fix macOS build (following Projucer changes made in Windows, which removed /Applications/JUCE/modules from its headers). move JUCE headers under source control, so that Windows and macOS can both build against same version of JUCE. remove AUv3 target (I think it's an iOS thing, so it will never work with this macOS fluidsynth dylib).

modules/juce_box2d/box2d/Dynamics/Joints/b2DistanceJoint.cpp

@@ -0,0 +1,260 @@
+/*
+* Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#include "b2DistanceJoint.h"
+#include "../b2Body.h"
+#include "../b2TimeStep.h"
+
+// 1-D constrained system
+// m (v2 - v1) = lambda
+// v2 + (beta/h) * x1 + gamma * lambda = 0, gamma has units of inverse mass.
+// x2 = x1 + h * v2
+
+// 1-D mass-damper-spring system
+// m (v2 - v1) + h * d * v2 + h * k *
+
+// C = norm(p2 - p1) - L
+// u = (p2 - p1) / norm(p2 - p1)
+// Cdot = dot(u, v2 + cross(w2, r2) - v1 - cross(w1, r1))
+// J = [-u -cross(r1, u) u cross(r2, u)]
+// K = J * invM * JT
+//   = invMass1 + invI1 * cross(r1, u)^2 + invMass2 + invI2 * cross(r2, u)^2
+
+void b2DistanceJointDef::Initialize(b2Body* b1, b2Body* b2,
+									const b2Vec2& anchor1, const b2Vec2& anchor2)
+{
+	bodyA = b1;
+	bodyB = b2;
+	localAnchorA = bodyA->GetLocalPoint(anchor1);
+	localAnchorB = bodyB->GetLocalPoint(anchor2);
+	b2Vec2 d = anchor2 - anchor1;
+	length = d.Length();
+}
+
+b2DistanceJoint::b2DistanceJoint(const b2DistanceJointDef* def)
+: b2Joint(def)
+{
+	m_localAnchorA = def->localAnchorA;
+	m_localAnchorB = def->localAnchorB;
+	m_length = def->length;
+	m_frequencyHz = def->frequencyHz;
+	m_dampingRatio = def->dampingRatio;
+	m_impulse = 0.0f;
+	m_gamma = 0.0f;
+	m_bias = 0.0f;
+}
+
+void b2DistanceJoint::InitVelocityConstraints(const b2SolverData& data)
+{
+	m_indexA = m_bodyA->m_islandIndex;
+	m_indexB = m_bodyB->m_islandIndex;
+	m_localCenterA = m_bodyA->m_sweep.localCenter;
+	m_localCenterB = m_bodyB->m_sweep.localCenter;
+	m_invMassA = m_bodyA->m_invMass;
+	m_invMassB = m_bodyB->m_invMass;
+	m_invIA = m_bodyA->m_invI;
+	m_invIB = m_bodyB->m_invI;
+
+	b2Vec2 cA = data.positions[m_indexA].c;
+	float32 aA = data.positions[m_indexA].a;
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float32 wA = data.velocities[m_indexA].w;
+
+	b2Vec2 cB = data.positions[m_indexB].c;
+	float32 aB = data.positions[m_indexB].a;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	b2Rot qA(aA), qB(aB);
+
+	m_rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
+	m_rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
+	m_u = cB + m_rB - cA - m_rA;
+
+	// Handle singularity.
+	float32 length = m_u.Length();
+	if (length > b2_linearSlop)
+	{
+		m_u *= 1.0f / length;
+	}
+	else
+	{
+		m_u.Set(0.0f, 0.0f);
+	}
+
+	float32 crAu = b2Cross(m_rA, m_u);
+	float32 crBu = b2Cross(m_rB, m_u);
+	float32 invMass = m_invMassA + m_invIA * crAu * crAu + m_invMassB + m_invIB * crBu * crBu;
+
+	// Compute the effective mass matrix.
+	m_mass = invMass != 0.0f ? 1.0f / invMass : 0.0f;
+
+	if (m_frequencyHz > 0.0f)
+	{
+		float32 C = length - m_length;
+
+		// Frequency
+		float32 omega = 2.0f * b2_pi * m_frequencyHz;
+
+		// Damping coefficient
+		float32 d = 2.0f * m_mass * m_dampingRatio * omega;
+
+		// Spring stiffness
+		float32 k = m_mass * omega * omega;
+
+		// magic formulas
+		float32 h = data.step.dt;
+		m_gamma = h * (d + h * k);
+		m_gamma = m_gamma != 0.0f ? 1.0f / m_gamma : 0.0f;
+		m_bias = C * h * k * m_gamma;
+
+		invMass += m_gamma;
+		m_mass = invMass != 0.0f ? 1.0f / invMass : 0.0f;
+	}
+	else
+	{
+		m_gamma = 0.0f;
+		m_bias = 0.0f;
+	}
+
+	if (data.step.warmStarting)
+	{
+		// Scale the impulse to support a variable time step.
+		m_impulse *= data.step.dtRatio;
+
+		b2Vec2 P = m_impulse * m_u;
+		vA -= m_invMassA * P;
+		wA -= m_invIA * b2Cross(m_rA, P);
+		vB += m_invMassB * P;
+		wB += m_invIB * b2Cross(m_rB, P);
+	}
+	else
+	{
+		m_impulse = 0.0f;
+	}
+
+	data.velocities[m_indexA].v = vA;
+	data.velocities[m_indexA].w = wA;
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+}
+
+void b2DistanceJoint::SolveVelocityConstraints(const b2SolverData& data)
+{
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float32 wA = data.velocities[m_indexA].w;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	// Cdot = dot(u, v + cross(w, r))
+	b2Vec2 vpA = vA + b2Cross(wA, m_rA);
+	b2Vec2 vpB = vB + b2Cross(wB, m_rB);
+	float32 Cdot = b2Dot(m_u, vpB - vpA);
+
+	float32 impulse = -m_mass * (Cdot + m_bias + m_gamma * m_impulse);
+	m_impulse += impulse;
+
+	b2Vec2 P = impulse * m_u;
+	vA -= m_invMassA * P;
+	wA -= m_invIA * b2Cross(m_rA, P);
+	vB += m_invMassB * P;
+	wB += m_invIB * b2Cross(m_rB, P);
+
+	data.velocities[m_indexA].v = vA;
+	data.velocities[m_indexA].w = wA;
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+}
+
+bool b2DistanceJoint::SolvePositionConstraints(const b2SolverData& data)
+{
+	if (m_frequencyHz > 0.0f)
+	{
+		// There is no position correction for soft distance constraints.
+		return true;
+	}
+
+	b2Vec2 cA = data.positions[m_indexA].c;
+	float32 aA = data.positions[m_indexA].a;
+	b2Vec2 cB = data.positions[m_indexB].c;
+	float32 aB = data.positions[m_indexB].a;
+
+	b2Rot qA(aA), qB(aB);
+
+	b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
+	b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
+	b2Vec2 u = cB + rB - cA - rA;
+
+	float32 length = u.Normalize();
+	float32 C = length - m_length;
+	C = b2Clamp(C, -b2_maxLinearCorrection, b2_maxLinearCorrection);
+
+	float32 impulse = -m_mass * C;
+	b2Vec2 P = impulse * u;
+
+	cA -= m_invMassA * P;
+	aA -= m_invIA * b2Cross(rA, P);
+	cB += m_invMassB * P;
+	aB += m_invIB * b2Cross(rB, P);
+
+	data.positions[m_indexA].c = cA;
+	data.positions[m_indexA].a = aA;
+	data.positions[m_indexB].c = cB;
+	data.positions[m_indexB].a = aB;
+
+	return b2Abs(C) < b2_linearSlop;
+}
+
+b2Vec2 b2DistanceJoint::GetAnchorA() const
+{
+	return m_bodyA->GetWorldPoint(m_localAnchorA);
+}
+
+b2Vec2 b2DistanceJoint::GetAnchorB() const
+{
+	return m_bodyB->GetWorldPoint(m_localAnchorB);
+}
+
+b2Vec2 b2DistanceJoint::GetReactionForce(float32 inv_dt) const
+{
+	b2Vec2 F = (inv_dt * m_impulse) * m_u;
+	return F;
+}
+
+float32 b2DistanceJoint::GetReactionTorque(float32 inv_dt) const
+{
+	B2_NOT_USED(inv_dt);
+	return 0.0f;
+}
+
+void b2DistanceJoint::Dump()
+{
+	int32 indexA = m_bodyA->m_islandIndex;
+	int32 indexB = m_bodyB->m_islandIndex;
+
+	b2Log("  b2DistanceJointDef jd;\n");
+	b2Log("  jd.bodyA = bodies[%d];\n", indexA);
+	b2Log("  jd.bodyB = bodies[%d];\n", indexB);
+	b2Log("  jd.collideConnected = bool(%d);\n", m_collideConnected);
+	b2Log("  jd.localAnchorA.Set(%.15lef, %.15lef);\n", m_localAnchorA.x, m_localAnchorA.y);
+	b2Log("  jd.localAnchorB.Set(%.15lef, %.15lef);\n", m_localAnchorB.x, m_localAnchorB.y);
+	b2Log("  jd.length = %.15lef;\n", m_length);
+	b2Log("  jd.frequencyHz = %.15lef;\n", m_frequencyHz);
+	b2Log("  jd.dampingRatio = %.15lef;\n", m_dampingRatio);
+	b2Log("  joints[%d] = m_world->CreateJoint(&jd);\n", m_index);
+}

modules/juce_box2d/box2d/Dynamics/Joints/b2DistanceJoint.h

@@ -0,0 +1,169 @@
+/*
+* Copyright (c) 2006-2007 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#ifndef B2_DISTANCE_JOINT_H
+#define B2_DISTANCE_JOINT_H
+
+#include "b2Joint.h"
+
+/// Distance joint definition. This requires defining an
+/// anchor point on both bodies and the non-zero length of the
+/// distance joint. The definition uses local anchor points
+/// so that the initial configuration can violate the constraint
+/// slightly. This helps when saving and loading a game.
+/// @warning Do not use a zero or short length.
+struct b2DistanceJointDef : public b2JointDef
+{
+	b2DistanceJointDef()
+	{
+		type = e_distanceJoint;
+		localAnchorA.Set(0.0f, 0.0f);
+		localAnchorB.Set(0.0f, 0.0f);
+		length = 1.0f;
+		frequencyHz = 0.0f;
+		dampingRatio = 0.0f;
+	}
+
+	/// Initialize the bodies, anchors, and length using the world
+	/// anchors.
+	void Initialize(b2Body* bodyA, b2Body* bodyB,
+					const b2Vec2& anchorA, const b2Vec2& anchorB);
+
+	/// The local anchor point relative to bodyA's origin.
+	b2Vec2 localAnchorA;
+
+	/// The local anchor point relative to bodyB's origin.
+	b2Vec2 localAnchorB;
+
+	/// The natural length between the anchor points.
+	float32 length;
+
+	/// The mass-spring-damper frequency in Hertz. A value of 0
+	/// disables softness.
+	float32 frequencyHz;
+
+	/// The damping ratio. 0 = no damping, 1 = critical damping.
+	float32 dampingRatio;
+};
+
+/// A distance joint constrains two points on two bodies
+/// to remain at a fixed distance from each other. You can view
+/// this as a massless, rigid rod.
+class b2DistanceJoint : public b2Joint
+{
+public:
+
+	b2Vec2 GetAnchorA() const;
+	b2Vec2 GetAnchorB() const;
+
+	/// Get the reaction force given the inverse time step.
+	/// Unit is N.
+	b2Vec2 GetReactionForce(float32 inv_dt) const;
+
+	/// Get the reaction torque given the inverse time step.
+	/// Unit is N*m. This is always zero for a distance joint.
+	float32 GetReactionTorque(float32 inv_dt) const;
+
+	/// The local anchor point relative to bodyA's origin.
+	const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }
+
+	/// The local anchor point relative to bodyB's origin.
+	const b2Vec2& GetLocalAnchorB() const  { return m_localAnchorB; }
+
+	/// Set/get the natural length.
+	/// Manipulating the length can lead to non-physical behavior when the frequency is zero.
+	void SetLength(float32 length);
+	float32 GetLength() const;
+
+	/// Set/get frequency in Hz.
+	void SetFrequency(float32 hz);
+	float32 GetFrequency() const;
+
+	/// Set/get damping ratio.
+	void SetDampingRatio(float32 ratio);
+	float32 GetDampingRatio() const;
+
+	/// Dump joint to dmLog
+	void Dump();
+
+protected:
+
+	friend class b2Joint;
+	b2DistanceJoint(const b2DistanceJointDef* data);
+
+	void InitVelocityConstraints(const b2SolverData& data);
+	void SolveVelocityConstraints(const b2SolverData& data);
+	bool SolvePositionConstraints(const b2SolverData& data);
+
+	float32 m_frequencyHz;
+	float32 m_dampingRatio;
+	float32 m_bias;
+
+	// Solver shared
+	b2Vec2 m_localAnchorA;
+	b2Vec2 m_localAnchorB;
+	float32 m_gamma;
+	float32 m_impulse;
+	float32 m_length;
+
+	// Solver temp
+	juce::int32 m_indexA;
+	juce::int32 m_indexB;
+	b2Vec2 m_u;
+	b2Vec2 m_rA;
+	b2Vec2 m_rB;
+	b2Vec2 m_localCenterA;
+	b2Vec2 m_localCenterB;
+	float32 m_invMassA;
+	float32 m_invMassB;
+	float32 m_invIA;
+	float32 m_invIB;
+	float32 m_mass;
+};
+
+inline void b2DistanceJoint::SetLength(float32 length)
+{
+	m_length = length;
+}
+
+inline float32 b2DistanceJoint::GetLength() const
+{
+	return m_length;
+}
+
+inline void b2DistanceJoint::SetFrequency(float32 hz)
+{
+	m_frequencyHz = hz;
+}
+
+inline float32 b2DistanceJoint::GetFrequency() const
+{
+	return m_frequencyHz;
+}
+
+inline void b2DistanceJoint::SetDampingRatio(float32 ratio)
+{
+	m_dampingRatio = ratio;
+}
+
+inline float32 b2DistanceJoint::GetDampingRatio() const
+{
+	return m_dampingRatio;
+}
+
+#endif

modules/juce_box2d/box2d/Dynamics/Joints/b2FrictionJoint.cpp

@@ -0,0 +1,251 @@
+/*
+* Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#include "b2FrictionJoint.h"
+#include "../b2Body.h"
+#include "../b2TimeStep.h"
+
+// Point-to-point constraint
+// Cdot = v2 - v1
+//      = v2 + cross(w2, r2) - v1 - cross(w1, r1)
+// J = [-I -r1_skew I r2_skew ]
+// Identity used:
+// w k % (rx i + ry j) = w * (-ry i + rx j)
+
+// Angle constraint
+// Cdot = w2 - w1
+// J = [0 0 -1 0 0 1]
+// K = invI1 + invI2
+
+void b2FrictionJointDef::Initialize(b2Body* bA, b2Body* bB, const b2Vec2& anchor)
+{
+	bodyA = bA;
+	bodyB = bB;
+	localAnchorA = bodyA->GetLocalPoint(anchor);
+	localAnchorB = bodyB->GetLocalPoint(anchor);
+}
+
+b2FrictionJoint::b2FrictionJoint(const b2FrictionJointDef* def)
+: b2Joint(def)
+{
+	m_localAnchorA = def->localAnchorA;
+	m_localAnchorB = def->localAnchorB;
+
+	m_linearImpulse.SetZero();
+	m_angularImpulse = 0.0f;
+
+	m_maxForce = def->maxForce;
+	m_maxTorque = def->maxTorque;
+}
+
+void b2FrictionJoint::InitVelocityConstraints(const b2SolverData& data)
+{
+	m_indexA = m_bodyA->m_islandIndex;
+	m_indexB = m_bodyB->m_islandIndex;
+	m_localCenterA = m_bodyA->m_sweep.localCenter;
+	m_localCenterB = m_bodyB->m_sweep.localCenter;
+	m_invMassA = m_bodyA->m_invMass;
+	m_invMassB = m_bodyB->m_invMass;
+	m_invIA = m_bodyA->m_invI;
+	m_invIB = m_bodyB->m_invI;
+
+	float32 aA = data.positions[m_indexA].a;
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float32 wA = data.velocities[m_indexA].w;
+
+	float32 aB = data.positions[m_indexB].a;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	b2Rot qA(aA), qB(aB);
+
+	// Compute the effective mass matrix.
+	m_rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
+	m_rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
+
+	// J = [-I -r1_skew I r2_skew]
+	//     [ 0       -1 0       1]
+	// r_skew = [-ry; rx]
+
+	// Matlab
+	// K = [ mA+r1y^2*iA+mB+r2y^2*iB,  -r1y*iA*r1x-r2y*iB*r2x,          -r1y*iA-r2y*iB]
+	//     [  -r1y*iA*r1x-r2y*iB*r2x, mA+r1x^2*iA+mB+r2x^2*iB,           r1x*iA+r2x*iB]
+	//     [          -r1y*iA-r2y*iB,           r1x*iA+r2x*iB,                   iA+iB]
+
+	float32 mA = m_invMassA, mB = m_invMassB;
+	float32 iA = m_invIA, iB = m_invIB;
+
+	b2Mat22 K;
+	K.ex.x = mA + mB + iA * m_rA.y * m_rA.y + iB * m_rB.y * m_rB.y;
+	K.ex.y = -iA * m_rA.x * m_rA.y - iB * m_rB.x * m_rB.y;
+	K.ey.x = K.ex.y;
+	K.ey.y = mA + mB + iA * m_rA.x * m_rA.x + iB * m_rB.x * m_rB.x;
+
+	m_linearMass = K.GetInverse();
+
+	m_angularMass = iA + iB;
+	if (m_angularMass > 0.0f)
+	{
+		m_angularMass = 1.0f / m_angularMass;
+	}
+
+	if (data.step.warmStarting)
+	{
+		// Scale impulses to support a variable time step.
+		m_linearImpulse *= data.step.dtRatio;
+		m_angularImpulse *= data.step.dtRatio;
+
+		b2Vec2 P(m_linearImpulse.x, m_linearImpulse.y);
+		vA -= mA * P;
+		wA -= iA * (b2Cross(m_rA, P) + m_angularImpulse);
+		vB += mB * P;
+		wB += iB * (b2Cross(m_rB, P) + m_angularImpulse);
+	}
+	else
+	{
+		m_linearImpulse.SetZero();
+		m_angularImpulse = 0.0f;
+	}
+
+	data.velocities[m_indexA].v = vA;
+	data.velocities[m_indexA].w = wA;
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+}
+
+void b2FrictionJoint::SolveVelocityConstraints(const b2SolverData& data)
+{
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float32 wA = data.velocities[m_indexA].w;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	float32 mA = m_invMassA, mB = m_invMassB;
+	float32 iA = m_invIA, iB = m_invIB;
+
+	float32 h = data.step.dt;
+
+	// Solve angular friction
+	{
+		float32 Cdot = wB - wA;
+		float32 impulse = -m_angularMass * Cdot;
+
+		float32 oldImpulse = m_angularImpulse;
+		float32 maxImpulse = h * m_maxTorque;
+		m_angularImpulse = b2Clamp(m_angularImpulse + impulse, -maxImpulse, maxImpulse);
+		impulse = m_angularImpulse - oldImpulse;
+
+		wA -= iA * impulse;
+		wB += iB * impulse;
+	}
+
+	// Solve linear friction
+	{
+		b2Vec2 Cdot = vB + b2Cross(wB, m_rB) - vA - b2Cross(wA, m_rA);
+
+		b2Vec2 impulse = -b2Mul(m_linearMass, Cdot);
+		b2Vec2 oldImpulse = m_linearImpulse;
+		m_linearImpulse += impulse;
+
+		float32 maxImpulse = h * m_maxForce;
+
+		if (m_linearImpulse.LengthSquared() > maxImpulse * maxImpulse)
+		{
+			m_linearImpulse.Normalize();
+			m_linearImpulse *= maxImpulse;
+		}
+
+		impulse = m_linearImpulse - oldImpulse;
+
+		vA -= mA * impulse;
+		wA -= iA * b2Cross(m_rA, impulse);
+
+		vB += mB * impulse;
+		wB += iB * b2Cross(m_rB, impulse);
+	}
+
+	data.velocities[m_indexA].v = vA;
+	data.velocities[m_indexA].w = wA;
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+}
+
+bool b2FrictionJoint::SolvePositionConstraints(const b2SolverData& data)
+{
+	B2_NOT_USED(data);
+
+	return true;
+}
+
+b2Vec2 b2FrictionJoint::GetAnchorA() const
+{
+	return m_bodyA->GetWorldPoint(m_localAnchorA);
+}
+
+b2Vec2 b2FrictionJoint::GetAnchorB() const
+{
+	return m_bodyB->GetWorldPoint(m_localAnchorB);
+}
+
+b2Vec2 b2FrictionJoint::GetReactionForce(float32 inv_dt) const
+{
+	return inv_dt * m_linearImpulse;
+}
+
+float32 b2FrictionJoint::GetReactionTorque(float32 inv_dt) const
+{
+	return inv_dt * m_angularImpulse;
+}
+
+void b2FrictionJoint::SetMaxForce(float32 force)
+{
+	b2Assert(b2IsValid(force) && force >= 0.0f);
+	m_maxForce = force;
+}
+
+float32 b2FrictionJoint::GetMaxForce() const
+{
+	return m_maxForce;
+}
+
+void b2FrictionJoint::SetMaxTorque(float32 torque)
+{
+	b2Assert(b2IsValid(torque) && torque >= 0.0f);
+	m_maxTorque = torque;
+}
+
+float32 b2FrictionJoint::GetMaxTorque() const
+{
+	return m_maxTorque;
+}
+
+void b2FrictionJoint::Dump()
+{
+	int32 indexA = m_bodyA->m_islandIndex;
+	int32 indexB = m_bodyB->m_islandIndex;
+
+	b2Log("  b2FrictionJointDef jd;\n");
+	b2Log("  jd.bodyA = bodies[%d];\n", indexA);
+	b2Log("  jd.bodyB = bodies[%d];\n", indexB);
+	b2Log("  jd.collideConnected = bool(%d);\n", m_collideConnected);
+	b2Log("  jd.localAnchorA.Set(%.15lef, %.15lef);\n", m_localAnchorA.x, m_localAnchorA.y);
+	b2Log("  jd.localAnchorB.Set(%.15lef, %.15lef);\n", m_localAnchorB.x, m_localAnchorB.y);
+	b2Log("  jd.maxForce = %.15lef;\n", m_maxForce);
+	b2Log("  jd.maxTorque = %.15lef;\n", m_maxTorque);
+	b2Log("  joints[%d] = m_world->CreateJoint(&jd);\n", m_index);
+}

modules/juce_box2d/box2d/Dynamics/Joints/b2FrictionJoint.h

@@ -0,0 +1,119 @@
+/*
+* Copyright (c) 2006-2007 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#ifndef B2_FRICTION_JOINT_H
+#define B2_FRICTION_JOINT_H
+
+#include "b2Joint.h"
+
+/// Friction joint definition.
+struct b2FrictionJointDef : public b2JointDef
+{
+	b2FrictionJointDef()
+	{
+		type = e_frictionJoint;
+		localAnchorA.SetZero();
+		localAnchorB.SetZero();
+		maxForce = 0.0f;
+		maxTorque = 0.0f;
+	}
+
+	/// Initialize the bodies, anchors, axis, and reference angle using the world
+	/// anchor and world axis.
+	void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor);
+
+	/// The local anchor point relative to bodyA's origin.
+	b2Vec2 localAnchorA;
+
+	/// The local anchor point relative to bodyB's origin.
+	b2Vec2 localAnchorB;
+
+	/// The maximum friction force in N.
+	float32 maxForce;
+
+	/// The maximum friction torque in N-m.
+	float32 maxTorque;
+};
+
+/// Friction joint. This is used for top-down friction.
+/// It provides 2D translational friction and angular friction.
+class b2FrictionJoint : public b2Joint
+{
+public:
+	b2Vec2 GetAnchorA() const;
+	b2Vec2 GetAnchorB() const;
+
+	b2Vec2 GetReactionForce(float32 inv_dt) const;
+	float32 GetReactionTorque(float32 inv_dt) const;
+
+	/// The local anchor point relative to bodyA's origin.
+	const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }
+
+	/// The local anchor point relative to bodyB's origin.
+	const b2Vec2& GetLocalAnchorB() const  { return m_localAnchorB; }
+
+	/// Set the maximum friction force in N.
+	void SetMaxForce(float32 force);
+
+	/// Get the maximum friction force in N.
+	float32 GetMaxForce() const;
+
+	/// Set the maximum friction torque in N*m.
+	void SetMaxTorque(float32 torque);
+
+	/// Get the maximum friction torque in N*m.
+	float32 GetMaxTorque() const;
+
+	/// Dump joint to dmLog
+	void Dump();
+
+protected:
+
+	friend class b2Joint;
+
+	b2FrictionJoint(const b2FrictionJointDef* def);
+
+	void InitVelocityConstraints(const b2SolverData& data);
+	void SolveVelocityConstraints(const b2SolverData& data);
+	bool SolvePositionConstraints(const b2SolverData& data);
+
+	b2Vec2 m_localAnchorA;
+	b2Vec2 m_localAnchorB;
+
+	// Solver shared
+	b2Vec2 m_linearImpulse;
+	float32 m_angularImpulse;
+	float32 m_maxForce;
+	float32 m_maxTorque;
+
+	// Solver temp
+	juce::int32 m_indexA;
+	juce::int32 m_indexB;
+	b2Vec2 m_rA;
+	b2Vec2 m_rB;
+	b2Vec2 m_localCenterA;
+	b2Vec2 m_localCenterB;
+	float32 m_invMassA;
+	float32 m_invMassB;
+	float32 m_invIA;
+	float32 m_invIB;
+	b2Mat22 m_linearMass;
+	float32 m_angularMass;
+};
+
+#endif

modules/juce_box2d/box2d/Dynamics/Joints/b2GearJoint.cpp

@@ -0,0 +1,419 @@
+/*
+* Copyright (c) 2007-2011 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#include "b2GearJoint.h"
+#include "b2RevoluteJoint.h"
+#include "b2PrismaticJoint.h"
+#include "../b2Body.h"
+#include "../b2TimeStep.h"
+
+// Gear Joint:
+// C0 = (coordinate1 + ratio * coordinate2)_initial
+// C = (coordinate1 + ratio * coordinate2) - C0 = 0
+// J = [J1 ratio * J2]
+// K = J * invM * JT
+//   = J1 * invM1 * J1T + ratio * ratio * J2 * invM2 * J2T
+//
+// Revolute:
+// coordinate = rotation
+// Cdot = angularVelocity
+// J = [0 0 1]
+// K = J * invM * JT = invI
+//
+// Prismatic:
+// coordinate = dot(p - pg, ug)
+// Cdot = dot(v + cross(w, r), ug)
+// J = [ug cross(r, ug)]
+// K = J * invM * JT = invMass + invI * cross(r, ug)^2
+
+b2GearJoint::b2GearJoint(const b2GearJointDef* def)
+: b2Joint(def)
+{
+	m_joint1 = def->joint1;
+	m_joint2 = def->joint2;
+
+	m_typeA = m_joint1->GetType();
+	m_typeB = m_joint2->GetType();
+
+	b2Assert(m_typeA == e_revoluteJoint || m_typeA == e_prismaticJoint);
+	b2Assert(m_typeB == e_revoluteJoint || m_typeB == e_prismaticJoint);
+
+	float32 coordinateA, coordinateB;
+
+	// TODO_ERIN there might be some problem with the joint edges in b2Joint.
+
+	m_bodyC = m_joint1->GetBodyA();
+	m_bodyA = m_joint1->GetBodyB();
+
+	// Get geometry of joint1
+	b2Transform xfA = m_bodyA->m_xf;
+	float32 aA = m_bodyA->m_sweep.a;
+	b2Transform xfC = m_bodyC->m_xf;
+	float32 aC = m_bodyC->m_sweep.a;
+
+	if (m_typeA == e_revoluteJoint)
+	{
+		b2RevoluteJoint* revolute = (b2RevoluteJoint*)def->joint1;
+		m_localAnchorC = revolute->m_localAnchorA;
+		m_localAnchorA = revolute->m_localAnchorB;
+		m_referenceAngleA = revolute->m_referenceAngle;
+		m_localAxisC.SetZero();
+
+		coordinateA = aA - aC - m_referenceAngleA;
+	}
+	else
+	{
+		b2PrismaticJoint* prismatic = (b2PrismaticJoint*)def->joint1;
+		m_localAnchorC = prismatic->m_localAnchorA;
+		m_localAnchorA = prismatic->m_localAnchorB;
+		m_referenceAngleA = prismatic->m_referenceAngle;
+		m_localAxisC = prismatic->m_localXAxisA;
+
+		b2Vec2 pC = m_localAnchorC;
+		b2Vec2 pA = b2MulT(xfC.q, b2Mul(xfA.q, m_localAnchorA) + (xfA.p - xfC.p));
+		coordinateA = b2Dot(pA - pC, m_localAxisC);
+	}
+
+	m_bodyD = m_joint2->GetBodyA();
+	m_bodyB = m_joint2->GetBodyB();
+
+	// Get geometry of joint2
+	b2Transform xfB = m_bodyB->m_xf;
+	float32 aB = m_bodyB->m_sweep.a;
+	b2Transform xfD = m_bodyD->m_xf;
+	float32 aD = m_bodyD->m_sweep.a;
+
+	if (m_typeB == e_revoluteJoint)
+	{
+		b2RevoluteJoint* revolute = (b2RevoluteJoint*)def->joint2;
+		m_localAnchorD = revolute->m_localAnchorA;
+		m_localAnchorB = revolute->m_localAnchorB;
+		m_referenceAngleB = revolute->m_referenceAngle;
+		m_localAxisD.SetZero();
+
+		coordinateB = aB - aD - m_referenceAngleB;
+	}
+	else
+	{
+		b2PrismaticJoint* prismatic = (b2PrismaticJoint*)def->joint2;
+		m_localAnchorD = prismatic->m_localAnchorA;
+		m_localAnchorB = prismatic->m_localAnchorB;
+		m_referenceAngleB = prismatic->m_referenceAngle;
+		m_localAxisD = prismatic->m_localXAxisA;
+
+		b2Vec2 pD = m_localAnchorD;
+		b2Vec2 pB = b2MulT(xfD.q, b2Mul(xfB.q, m_localAnchorB) + (xfB.p - xfD.p));
+		coordinateB = b2Dot(pB - pD, m_localAxisD);
+	}
+
+	m_ratio = def->ratio;
+
+	m_constant = coordinateA + m_ratio * coordinateB;
+
+	m_impulse = 0.0f;
+}
+
+void b2GearJoint::InitVelocityConstraints(const b2SolverData& data)
+{
+	m_indexA = m_bodyA->m_islandIndex;
+	m_indexB = m_bodyB->m_islandIndex;
+	m_indexC = m_bodyC->m_islandIndex;
+	m_indexD = m_bodyD->m_islandIndex;
+	m_lcA = m_bodyA->m_sweep.localCenter;
+	m_lcB = m_bodyB->m_sweep.localCenter;
+	m_lcC = m_bodyC->m_sweep.localCenter;
+	m_lcD = m_bodyD->m_sweep.localCenter;
+	m_mA = m_bodyA->m_invMass;
+	m_mB = m_bodyB->m_invMass;
+	m_mC = m_bodyC->m_invMass;
+	m_mD = m_bodyD->m_invMass;
+	m_iA = m_bodyA->m_invI;
+	m_iB = m_bodyB->m_invI;
+	m_iC = m_bodyC->m_invI;
+	m_iD = m_bodyD->m_invI;
+
+	float32 aA = data.positions[m_indexA].a;
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float32 wA = data.velocities[m_indexA].w;
+
+	float32 aB = data.positions[m_indexB].a;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	float32 aC = data.positions[m_indexC].a;
+	b2Vec2 vC = data.velocities[m_indexC].v;
+	float32 wC = data.velocities[m_indexC].w;
+
+	float32 aD = data.positions[m_indexD].a;
+	b2Vec2 vD = data.velocities[m_indexD].v;
+	float32 wD = data.velocities[m_indexD].w;
+
+	b2Rot qA(aA), qB(aB), qC(aC), qD(aD);
+
+	m_mass = 0.0f;
+
+	if (m_typeA == e_revoluteJoint)
+	{
+		m_JvAC.SetZero();
+		m_JwA = 1.0f;
+		m_JwC = 1.0f;
+		m_mass += m_iA + m_iC;
+	}
+	else
+	{
+		b2Vec2 u = b2Mul(qC, m_localAxisC);
+		b2Vec2 rC = b2Mul(qC, m_localAnchorC - m_lcC);
+		b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_lcA);
+		m_JvAC = u;
+		m_JwC = b2Cross(rC, u);
+		m_JwA = b2Cross(rA, u);
+		m_mass += m_mC + m_mA + m_iC * m_JwC * m_JwC + m_iA * m_JwA * m_JwA;
+	}
+
+	if (m_typeB == e_revoluteJoint)
+	{
+		m_JvBD.SetZero();
+		m_JwB = m_ratio;
+		m_JwD = m_ratio;
+		m_mass += m_ratio * m_ratio * (m_iB + m_iD);
+	}
+	else
+	{
+		b2Vec2 u = b2Mul(qD, m_localAxisD);
+		b2Vec2 rD = b2Mul(qD, m_localAnchorD - m_lcD);
+		b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_lcB);
+		m_JvBD = m_ratio * u;
+		m_JwD = m_ratio * b2Cross(rD, u);
+		m_JwB = m_ratio * b2Cross(rB, u);
+		m_mass += m_ratio * m_ratio * (m_mD + m_mB) + m_iD * m_JwD * m_JwD + m_iB * m_JwB * m_JwB;
+	}
+
+	// Compute effective mass.
+	m_mass = m_mass > 0.0f ? 1.0f / m_mass : 0.0f;
+
+	if (data.step.warmStarting)
+	{
+		vA += (m_mA * m_impulse) * m_JvAC;
+		wA += m_iA * m_impulse * m_JwA;
+		vB += (m_mB * m_impulse) * m_JvBD;
+		wB += m_iB * m_impulse * m_JwB;
+		vC -= (m_mC * m_impulse) * m_JvAC;
+		wC -= m_iC * m_impulse * m_JwC;
+		vD -= (m_mD * m_impulse) * m_JvBD;
+		wD -= m_iD * m_impulse * m_JwD;
+	}
+	else
+	{
+		m_impulse = 0.0f;
+	}
+
+	data.velocities[m_indexA].v = vA;
+	data.velocities[m_indexA].w = wA;
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+	data.velocities[m_indexC].v = vC;
+	data.velocities[m_indexC].w = wC;
+	data.velocities[m_indexD].v = vD;
+	data.velocities[m_indexD].w = wD;
+}
+
+void b2GearJoint::SolveVelocityConstraints(const b2SolverData& data)
+{
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float32 wA = data.velocities[m_indexA].w;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+	b2Vec2 vC = data.velocities[m_indexC].v;
+	float32 wC = data.velocities[m_indexC].w;
+	b2Vec2 vD = data.velocities[m_indexD].v;
+	float32 wD = data.velocities[m_indexD].w;
+
+	float32 Cdot = b2Dot(m_JvAC, vA - vC) + b2Dot(m_JvBD, vB - vD);
+	Cdot += (m_JwA * wA - m_JwC * wC) + (m_JwB * wB - m_JwD * wD);
+
+	float32 impulse = -m_mass * Cdot;
+	m_impulse += impulse;
+
+	vA += (m_mA * impulse) * m_JvAC;
+	wA += m_iA * impulse * m_JwA;
+	vB += (m_mB * impulse) * m_JvBD;
+	wB += m_iB * impulse * m_JwB;
+	vC -= (m_mC * impulse) * m_JvAC;
+	wC -= m_iC * impulse * m_JwC;
+	vD -= (m_mD * impulse) * m_JvBD;
+	wD -= m_iD * impulse * m_JwD;
+
+	data.velocities[m_indexA].v = vA;
+	data.velocities[m_indexA].w = wA;
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+	data.velocities[m_indexC].v = vC;
+	data.velocities[m_indexC].w = wC;
+	data.velocities[m_indexD].v = vD;
+	data.velocities[m_indexD].w = wD;
+}
+
+bool b2GearJoint::SolvePositionConstraints(const b2SolverData& data)
+{
+	b2Vec2 cA = data.positions[m_indexA].c;
+	float32 aA = data.positions[m_indexA].a;
+	b2Vec2 cB = data.positions[m_indexB].c;
+	float32 aB = data.positions[m_indexB].a;
+	b2Vec2 cC = data.positions[m_indexC].c;
+	float32 aC = data.positions[m_indexC].a;
+	b2Vec2 cD = data.positions[m_indexD].c;
+	float32 aD = data.positions[m_indexD].a;
+
+	b2Rot qA(aA), qB(aB), qC(aC), qD(aD);
+
+	float32 linearError = 0.0f;
+
+	float32 coordinateA, coordinateB;
+
+	b2Vec2 JvAC, JvBD;
+	float32 JwA, JwB, JwC, JwD;
+	float32 mass = 0.0f;
+
+	if (m_typeA == e_revoluteJoint)
+	{
+		JvAC.SetZero();
+		JwA = 1.0f;
+		JwC = 1.0f;
+		mass += m_iA + m_iC;
+
+		coordinateA = aA - aC - m_referenceAngleA;
+	}
+	else
+	{
+		b2Vec2 u = b2Mul(qC, m_localAxisC);
+		b2Vec2 rC = b2Mul(qC, m_localAnchorC - m_lcC);
+		b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_lcA);
+		JvAC = u;
+		JwC = b2Cross(rC, u);
+		JwA = b2Cross(rA, u);
+		mass += m_mC + m_mA + m_iC * JwC * JwC + m_iA * JwA * JwA;
+
+		b2Vec2 pC = m_localAnchorC - m_lcC;
+		b2Vec2 pA = b2MulT(qC, rA + (cA - cC));
+		coordinateA = b2Dot(pA - pC, m_localAxisC);
+	}
+
+	if (m_typeB == e_revoluteJoint)
+	{
+		JvBD.SetZero();
+		JwB = m_ratio;
+		JwD = m_ratio;
+		mass += m_ratio * m_ratio * (m_iB + m_iD);
+
+		coordinateB = aB - aD - m_referenceAngleB;
+	}
+	else
+	{
+		b2Vec2 u = b2Mul(qD, m_localAxisD);
+		b2Vec2 rD = b2Mul(qD, m_localAnchorD - m_lcD);
+		b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_lcB);
+		JvBD = m_ratio * u;
+		JwD = m_ratio * b2Cross(rD, u);
+		JwB = m_ratio * b2Cross(rB, u);
+		mass += m_ratio * m_ratio * (m_mD + m_mB) + m_iD * JwD * JwD + m_iB * JwB * JwB;
+
+		b2Vec2 pD = m_localAnchorD - m_lcD;
+		b2Vec2 pB = b2MulT(qD, rB + (cB - cD));
+		coordinateB = b2Dot(pB - pD, m_localAxisD);
+	}
+
+	float32 C = (coordinateA + m_ratio * coordinateB) - m_constant;
+
+	float32 impulse = 0.0f;
+	if (mass > 0.0f)
+	{
+		impulse = -C / mass;
+	}
+
+	cA += m_mA * impulse * JvAC;
+	aA += m_iA * impulse * JwA;
+	cB += m_mB * impulse * JvBD;
+	aB += m_iB * impulse * JwB;
+	cC -= m_mC * impulse * JvAC;
+	aC -= m_iC * impulse * JwC;
+	cD -= m_mD * impulse * JvBD;
+	aD -= m_iD * impulse * JwD;
+
+	data.positions[m_indexA].c = cA;
+	data.positions[m_indexA].a = aA;
+	data.positions[m_indexB].c = cB;
+	data.positions[m_indexB].a = aB;
+	data.positions[m_indexC].c = cC;
+	data.positions[m_indexC].a = aC;
+	data.positions[m_indexD].c = cD;
+	data.positions[m_indexD].a = aD;
+
+	// TODO_ERIN not implemented
+	return linearError < b2_linearSlop;
+}
+
+b2Vec2 b2GearJoint::GetAnchorA() const
+{
+	return m_bodyA->GetWorldPoint(m_localAnchorA);
+}
+
+b2Vec2 b2GearJoint::GetAnchorB() const
+{
+	return m_bodyB->GetWorldPoint(m_localAnchorB);
+}
+
+b2Vec2 b2GearJoint::GetReactionForce(float32 inv_dt) const
+{
+	b2Vec2 P = m_impulse * m_JvAC;
+	return inv_dt * P;
+}
+
+float32 b2GearJoint::GetReactionTorque(float32 inv_dt) const
+{
+	float32 L = m_impulse * m_JwA;
+	return inv_dt * L;
+}
+
+void b2GearJoint::SetRatio(float32 ratio)
+{
+	b2Assert(b2IsValid(ratio));
+	m_ratio = ratio;
+}
+
+float32 b2GearJoint::GetRatio() const
+{
+	return m_ratio;
+}
+
+void b2GearJoint::Dump()
+{
+	int32 indexA = m_bodyA->m_islandIndex;
+	int32 indexB = m_bodyB->m_islandIndex;
+
+	int32 index1 = m_joint1->m_index;
+	int32 index2 = m_joint2->m_index;
+
+	b2Log("  b2GearJointDef jd;\n");
+	b2Log("  jd.bodyA = bodies[%d];\n", indexA);
+	b2Log("  jd.bodyB = bodies[%d];\n", indexB);
+	b2Log("  jd.collideConnected = bool(%d);\n", m_collideConnected);
+	b2Log("  jd.joint1 = joints[%d];\n", index1);
+	b2Log("  jd.joint2 = joints[%d];\n", index2);
+	b2Log("  jd.ratio = %.15lef;\n", m_ratio);
+	b2Log("  joints[%d] = m_world->CreateJoint(&jd);\n", m_index);
+}

modules/juce_box2d/box2d/Dynamics/Joints/b2GearJoint.h

@@ -0,0 +1,125 @@
+/*
+* Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#ifndef B2_GEAR_JOINT_H
+#define B2_GEAR_JOINT_H
+
+#include "b2Joint.h"
+
+/// Gear joint definition. This definition requires two existing
+/// revolute or prismatic joints (any combination will work).
+struct b2GearJointDef : public b2JointDef
+{
+	b2GearJointDef()
+	{
+		type = e_gearJoint;
+		joint1 = NULL;
+		joint2 = NULL;
+		ratio = 1.0f;
+	}
+
+	/// The first revolute/prismatic joint attached to the gear joint.
+	b2Joint* joint1;
+
+	/// The second revolute/prismatic joint attached to the gear joint.
+	b2Joint* joint2;
+
+	/// The gear ratio.
+	/// @see b2GearJoint for explanation.
+	float32 ratio;
+};
+
+/// A gear joint is used to connect two joints together. Either joint
+/// can be a revolute or prismatic joint. You specify a gear ratio
+/// to bind the motions together:
+/// coordinate1 + ratio * coordinate2 = constant
+/// The ratio can be negative or positive. If one joint is a revolute joint
+/// and the other joint is a prismatic joint, then the ratio will have units
+/// of length or units of 1/length.
+/// @warning You have to manually destroy the gear joint if joint1 or joint2
+/// is destroyed.
+class b2GearJoint : public b2Joint
+{
+public:
+	b2Vec2 GetAnchorA() const;
+	b2Vec2 GetAnchorB() const;
+
+	b2Vec2 GetReactionForce(float32 inv_dt) const;
+	float32 GetReactionTorque(float32 inv_dt) const;
+
+	/// Get the first joint.
+	b2Joint* GetJoint1() { return m_joint1; }
+
+	/// Get the second joint.
+	b2Joint* GetJoint2() { return m_joint2; }
+
+	/// Set/Get the gear ratio.
+	void SetRatio(float32 ratio);
+	float32 GetRatio() const;
+
+	/// Dump joint to dmLog
+	void Dump();
+
+protected:
+
+	friend class b2Joint;
+	b2GearJoint(const b2GearJointDef* data);
+
+	void InitVelocityConstraints(const b2SolverData& data);
+	void SolveVelocityConstraints(const b2SolverData& data);
+	bool SolvePositionConstraints(const b2SolverData& data);
+
+	b2Joint* m_joint1;
+	b2Joint* m_joint2;
+
+	b2JointType m_typeA;
+	b2JointType m_typeB;
+
+	// Body A is connected to body C
+	// Body B is connected to body D
+	b2Body* m_bodyC;
+	b2Body* m_bodyD;
+
+	// Solver shared
+	b2Vec2 m_localAnchorA;
+	b2Vec2 m_localAnchorB;
+	b2Vec2 m_localAnchorC;
+	b2Vec2 m_localAnchorD;
+
+	b2Vec2 m_localAxisC;
+	b2Vec2 m_localAxisD;
+
+	float32 m_referenceAngleA;
+	float32 m_referenceAngleB;
+
+	float32 m_constant;
+	float32 m_ratio;
+
+	float32 m_impulse;
+
+	// Solver temp
+	juce::int32 m_indexA, m_indexB, m_indexC, m_indexD;
+	b2Vec2 m_lcA, m_lcB, m_lcC, m_lcD;
+	float32 m_mA, m_mB, m_mC, m_mD;
+	float32 m_iA, m_iB, m_iC, m_iD;
+	b2Vec2 m_JvAC, m_JvBD;
+	float32 m_JwA, m_JwB, m_JwC, m_JwD;
+	float32 m_mass;
+};
+
+#endif

modules/juce_box2d/box2d/Dynamics/Joints/b2Joint.cpp

@@ -0,0 +1,199 @@
+/*
+* Copyright (c) 2006-2007 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#include "b2Joint.h"
+#include "b2DistanceJoint.h"
+#include "b2WheelJoint.h"
+#include "b2MouseJoint.h"
+#include "b2RevoluteJoint.h"
+#include "b2PrismaticJoint.h"
+#include "b2PulleyJoint.h"
+#include "b2GearJoint.h"
+#include "b2WeldJoint.h"
+#include "b2FrictionJoint.h"
+#include "b2RopeJoint.h"
+#include "../b2Body.h"
+#include "../b2World.h"
+#include "../../Common/b2BlockAllocator.h"
+
+#include <new>
+
+b2Joint* b2Joint::Create(const b2JointDef* def, b2BlockAllocator* allocator)
+{
+	b2Joint* joint = NULL;
+
+	switch (def->type)
+	{
+	case e_distanceJoint:
+		{
+			void* mem = allocator->Allocate(sizeof(b2DistanceJoint));
+			joint = new (mem) b2DistanceJoint((b2DistanceJointDef*)def);
+		}
+		break;
+
+	case e_mouseJoint:
+		{
+			void* mem = allocator->Allocate(sizeof(b2MouseJoint));
+			joint = new (mem) b2MouseJoint((b2MouseJointDef*)def);
+		}
+		break;
+
+	case e_prismaticJoint:
+		{
+			void* mem = allocator->Allocate(sizeof(b2PrismaticJoint));
+			joint = new (mem) b2PrismaticJoint((b2PrismaticJointDef*)def);
+		}
+		break;
+
+	case e_revoluteJoint:
+		{
+			void* mem = allocator->Allocate(sizeof(b2RevoluteJoint));
+			joint = new (mem) b2RevoluteJoint((b2RevoluteJointDef*)def);
+		}
+		break;
+
+	case e_pulleyJoint:
+		{
+			void* mem = allocator->Allocate(sizeof(b2PulleyJoint));
+			joint = new (mem) b2PulleyJoint((b2PulleyJointDef*)def);
+		}
+		break;
+
+	case e_gearJoint:
+		{
+			void* mem = allocator->Allocate(sizeof(b2GearJoint));
+			joint = new (mem) b2GearJoint((b2GearJointDef*)def);
+		}
+		break;
+
+	case e_wheelJoint:
+		{
+			void* mem = allocator->Allocate(sizeof(b2WheelJoint));
+			joint = new (mem) b2WheelJoint((b2WheelJointDef*)def);
+		}
+		break;
+
+	case e_weldJoint:
+		{
+			void* mem = allocator->Allocate(sizeof(b2WeldJoint));
+			joint = new (mem) b2WeldJoint((b2WeldJointDef*)def);
+		}
+		break;
+
+	case e_frictionJoint:
+		{
+			void* mem = allocator->Allocate(sizeof(b2FrictionJoint));
+			joint = new (mem) b2FrictionJoint((b2FrictionJointDef*)def);
+		}
+		break;
+
+	case e_ropeJoint:
+		{
+			void* mem = allocator->Allocate(sizeof(b2RopeJoint));
+			joint = new (mem) b2RopeJoint((b2RopeJointDef*)def);
+		}
+		break;
+
+	default:
+		b2Assert(false);
+		break;
+	}
+
+	return joint;
+}
+
+void b2Joint::Destroy(b2Joint* joint, b2BlockAllocator* allocator)
+{
+	joint->~b2Joint();
+	switch (joint->m_type)
+	{
+	case e_distanceJoint:
+		allocator->Free(joint, sizeof(b2DistanceJoint));
+		break;
+
+	case e_mouseJoint:
+		allocator->Free(joint, sizeof(b2MouseJoint));
+		break;
+
+	case e_prismaticJoint:
+		allocator->Free(joint, sizeof(b2PrismaticJoint));
+		break;
+
+	case e_revoluteJoint:
+		allocator->Free(joint, sizeof(b2RevoluteJoint));
+		break;
+
+	case e_pulleyJoint:
+		allocator->Free(joint, sizeof(b2PulleyJoint));
+		break;
+
+	case e_gearJoint:
+		allocator->Free(joint, sizeof(b2GearJoint));
+		break;
+
+	case e_wheelJoint:
+		allocator->Free(joint, sizeof(b2WheelJoint));
+		break;
+
+	case e_weldJoint:
+		allocator->Free(joint, sizeof(b2WeldJoint));
+		break;
+
+	case e_frictionJoint:
+		allocator->Free(joint, sizeof(b2FrictionJoint));
+		break;
+
+	case e_ropeJoint:
+		allocator->Free(joint, sizeof(b2RopeJoint));
+		break;
+
+	default:
+		b2Assert(false);
+		break;
+	}
+}
+
+b2Joint::b2Joint(const b2JointDef* def)
+{
+	b2Assert(def->bodyA != def->bodyB);
+
+	m_type = def->type;
+	m_prev = NULL;
+	m_next = NULL;
+	m_bodyA = def->bodyA;
+	m_bodyB = def->bodyB;
+	m_index = 0;
+	m_collideConnected = def->collideConnected;
+	m_islandFlag = false;
+	m_userData = def->userData;
+
+	m_edgeA.joint = NULL;
+	m_edgeA.other = NULL;
+	m_edgeA.prev = NULL;
+	m_edgeA.next = NULL;
+
+	m_edgeB.joint = NULL;
+	m_edgeB.other = NULL;
+	m_edgeB.prev = NULL;
+	m_edgeB.next = NULL;
+}
+
+bool b2Joint::IsActive() const
+{
+	return m_bodyA->IsActive() && m_bodyB->IsActive();
+}

modules/juce_box2d/box2d/Dynamics/Joints/b2Joint.h

@@ -0,0 +1,222 @@
+/*
+* Copyright (c) 2006-2007 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#ifndef B2_JOINT_H
+#define B2_JOINT_H
+
+#include "../../Common/b2Math.h"
+
+class b2Body;
+class b2Joint;
+struct b2SolverData;
+class b2BlockAllocator;
+
+enum b2JointType
+{
+	e_unknownJoint,
+	e_revoluteJoint,
+	e_prismaticJoint,
+	e_distanceJoint,
+	e_pulleyJoint,
+	e_mouseJoint,
+	e_gearJoint,
+	e_wheelJoint,
+    e_weldJoint,
+	e_frictionJoint,
+	e_ropeJoint
+};
+
+enum b2LimitState
+{
+	e_inactiveLimit,
+	e_atLowerLimit,
+	e_atUpperLimit,
+	e_equalLimits
+};
+
+struct b2Jacobian
+{
+	b2Vec2 linear;
+	float32 angularA;
+	float32 angularB;
+};
+
+/// A joint edge is used to connect bodies and joints together
+/// in a joint graph where each body is a node and each joint
+/// is an edge. A joint edge belongs to a doubly linked list
+/// maintained in each attached body. Each joint has two joint
+/// nodes, one for each attached body.
+struct b2JointEdge
+{
+	b2Body* other;			///< provides quick access to the other body attached.
+	b2Joint* joint;			///< the joint
+	b2JointEdge* prev;		///< the previous joint edge in the body's joint list
+	b2JointEdge* next;		///< the next joint edge in the body's joint list
+};
+
+/// Joint definitions are used to construct joints.
+struct b2JointDef
+{
+	b2JointDef()
+	{
+		type = e_unknownJoint;
+		userData = NULL;
+		bodyA = NULL;
+		bodyB = NULL;
+		collideConnected = false;
+	}
+
+	/// The joint type is set automatically for concrete joint types.
+	b2JointType type;
+
+	/// Use this to attach application specific data to your joints.
+	void* userData;
+
+	/// The first attached body.
+	b2Body* bodyA;
+
+	/// The second attached body.
+	b2Body* bodyB;
+
+	/// Set this flag to true if the attached bodies should collide.
+	bool collideConnected;
+};
+
+/// The base joint class. Joints are used to constraint two bodies together in
+/// various fashions. Some joints also feature limits and motors.
+class b2Joint
+{
+public:
+
+	/// Get the type of the concrete joint.
+	b2JointType GetType() const;
+
+	/// Get the first body attached to this joint.
+	b2Body* GetBodyA();
+
+	/// Get the second body attached to this joint.
+	b2Body* GetBodyB();
+
+	/// Get the anchor point on bodyA in world coordinates.
+	virtual b2Vec2 GetAnchorA() const = 0;
+
+	/// Get the anchor point on bodyB in world coordinates.
+	virtual b2Vec2 GetAnchorB() const = 0;
+
+	/// Get the reaction force on bodyB at the joint anchor in Newtons.
+	virtual b2Vec2 GetReactionForce(float32 inv_dt) const = 0;
+
+	/// Get the reaction torque on bodyB in N*m.
+	virtual float32 GetReactionTorque(float32 inv_dt) const = 0;
+
+	/// Get the next joint the world joint list.
+	b2Joint* GetNext();
+	const b2Joint* GetNext() const;
+
+	/// Get the user data pointer.
+	void* GetUserData() const;
+
+	/// Set the user data pointer.
+	void SetUserData(void* data);
+
+	/// Short-cut function to determine if either body is inactive.
+	bool IsActive() const;
+
+	/// Get collide connected.
+	/// Note: modifying the collide connect flag won't work correctly because
+	/// the flag is only checked when fixture AABBs begin to overlap.
+	bool GetCollideConnected() const;
+
+	/// Dump this joint to the log file.
+	virtual void Dump() { b2Log("// Dump is not supported for this joint type.\n"); }
+
+protected:
+	friend class b2World;
+	friend class b2Body;
+	friend class b2Island;
+	friend class b2GearJoint;
+
+	static b2Joint* Create(const b2JointDef* def, b2BlockAllocator* allocator);
+	static void Destroy(b2Joint* joint, b2BlockAllocator* allocator);
+
+	b2Joint(const b2JointDef* def);
+	virtual ~b2Joint() {}
+
+	virtual void InitVelocityConstraints(const b2SolverData& data) = 0;
+	virtual void SolveVelocityConstraints(const b2SolverData& data) = 0;
+
+	// This returns true if the position errors are within tolerance.
+	virtual bool SolvePositionConstraints(const b2SolverData& data) = 0;
+
+	b2JointType m_type;
+	b2Joint* m_prev;
+	b2Joint* m_next;
+	b2JointEdge m_edgeA;
+	b2JointEdge m_edgeB;
+	b2Body* m_bodyA;
+	b2Body* m_bodyB;
+
+	juce::int32 m_index;
+
+	bool m_islandFlag;
+	bool m_collideConnected;
+
+	void* m_userData;
+};
+
+inline b2JointType b2Joint::GetType() const
+{
+	return m_type;
+}
+
+inline b2Body* b2Joint::GetBodyA()
+{
+	return m_bodyA;
+}
+
+inline b2Body* b2Joint::GetBodyB()
+{
+	return m_bodyB;
+}
+
+inline b2Joint* b2Joint::GetNext()
+{
+	return m_next;
+}
+
+inline const b2Joint* b2Joint::GetNext() const
+{
+	return m_next;
+}
+
+inline void* b2Joint::GetUserData() const
+{
+	return m_userData;
+}
+
+inline void b2Joint::SetUserData(void* data)
+{
+	m_userData = data;
+}
+
+inline bool b2Joint::GetCollideConnected() const
+{
+	return m_collideConnected;
+}
+
+#endif

modules/juce_box2d/box2d/Dynamics/Joints/b2MouseJoint.cpp

@@ -0,0 +1,217 @@
+/*
+* Copyright (c) 2006-2007 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#include "b2MouseJoint.h"
+#include "../b2Body.h"
+#include "../b2TimeStep.h"
+
+// p = attached point, m = mouse point
+// C = p - m
+// Cdot = v
+//      = v + cross(w, r)
+// J = [I r_skew]
+// Identity used:
+// w k % (rx i + ry j) = w * (-ry i + rx j)
+
+b2MouseJoint::b2MouseJoint(const b2MouseJointDef* def)
+: b2Joint(def)
+{
+	b2Assert(def->target.IsValid());
+	b2Assert(b2IsValid(def->maxForce) && def->maxForce >= 0.0f);
+	b2Assert(b2IsValid(def->frequencyHz) && def->frequencyHz >= 0.0f);
+	b2Assert(b2IsValid(def->dampingRatio) && def->dampingRatio >= 0.0f);
+
+	m_targetA = def->target;
+	m_localAnchorB = b2MulT(m_bodyB->GetTransform(), m_targetA);
+
+	m_maxForce = def->maxForce;
+	m_impulse.SetZero();
+
+	m_frequencyHz = def->frequencyHz;
+	m_dampingRatio = def->dampingRatio;
+
+	m_beta = 0.0f;
+	m_gamma = 0.0f;
+}
+
+void b2MouseJoint::SetTarget(const b2Vec2& target)
+{
+	if (m_bodyB->IsAwake() == false)
+	{
+		m_bodyB->SetAwake(true);
+	}
+	m_targetA = target;
+}
+
+const b2Vec2& b2MouseJoint::GetTarget() const
+{
+	return m_targetA;
+}
+
+void b2MouseJoint::SetMaxForce(float32 force)
+{
+	m_maxForce = force;
+}
+
+float32 b2MouseJoint::GetMaxForce() const
+{
+	return m_maxForce;
+}
+
+void b2MouseJoint::SetFrequency(float32 hz)
+{
+	m_frequencyHz = hz;
+}
+
+float32 b2MouseJoint::GetFrequency() const
+{
+	return m_frequencyHz;
+}
+
+void b2MouseJoint::SetDampingRatio(float32 ratio)
+{
+	m_dampingRatio = ratio;
+}
+
+float32 b2MouseJoint::GetDampingRatio() const
+{
+	return m_dampingRatio;
+}
+
+void b2MouseJoint::InitVelocityConstraints(const b2SolverData& data)
+{
+	m_indexB = m_bodyB->m_islandIndex;
+	m_localCenterB = m_bodyB->m_sweep.localCenter;
+	m_invMassB = m_bodyB->m_invMass;
+	m_invIB = m_bodyB->m_invI;
+
+	b2Vec2 cB = data.positions[m_indexB].c;
+	float32 aB = data.positions[m_indexB].a;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	b2Rot qB(aB);
+
+	float32 mass = m_bodyB->GetMass();
+
+	// Frequency
+	float32 omega = 2.0f * b2_pi * m_frequencyHz;
+
+	// Damping coefficient
+	float32 d = 2.0f * mass * m_dampingRatio * omega;
+
+	// Spring stiffness
+	float32 k = mass * (omega * omega);
+
+	// magic formulas
+	// gamma has units of inverse mass.
+	// beta has units of inverse time.
+	float32 h = data.step.dt;
+	b2Assert(d + h * k > b2_epsilon);
+	m_gamma = h * (d + h * k);
+	if (m_gamma != 0.0f)
+	{
+		m_gamma = 1.0f / m_gamma;
+	}
+	m_beta = h * k * m_gamma;
+
+	// Compute the effective mass matrix.
+	m_rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
+
+	// K    = [(1/m1 + 1/m2) * eye(2) - skew(r1) * invI1 * skew(r1) - skew(r2) * invI2 * skew(r2)]
+	//      = [1/m1+1/m2     0    ] + invI1 * [r1.y*r1.y -r1.x*r1.y] + invI2 * [r1.y*r1.y -r1.x*r1.y]
+	//        [    0     1/m1+1/m2]           [-r1.x*r1.y r1.x*r1.x]           [-r1.x*r1.y r1.x*r1.x]
+	b2Mat22 K;
+	K.ex.x = m_invMassB + m_invIB * m_rB.y * m_rB.y + m_gamma;
+	K.ex.y = -m_invIB * m_rB.x * m_rB.y;
+	K.ey.x = K.ex.y;
+	K.ey.y = m_invMassB + m_invIB * m_rB.x * m_rB.x + m_gamma;
+
+	m_mass = K.GetInverse();
+
+	m_C = cB + m_rB - m_targetA;
+	m_C *= m_beta;
+
+	// Cheat with some damping
+	wB *= 0.98f;
+
+	if (data.step.warmStarting)
+	{
+		m_impulse *= data.step.dtRatio;
+		vB += m_invMassB * m_impulse;
+		wB += m_invIB * b2Cross(m_rB, m_impulse);
+	}
+	else
+	{
+		m_impulse.SetZero();
+	}
+
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+}
+
+void b2MouseJoint::SolveVelocityConstraints(const b2SolverData& data)
+{
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	// Cdot = v + cross(w, r)
+	b2Vec2 Cdot = vB + b2Cross(wB, m_rB);
+	b2Vec2 impulse = b2Mul(m_mass, -(Cdot + m_C + m_gamma * m_impulse));
+
+	b2Vec2 oldImpulse = m_impulse;
+	m_impulse += impulse;
+	float32 maxImpulse = data.step.dt * m_maxForce;
+	if (m_impulse.LengthSquared() > maxImpulse * maxImpulse)
+	{
+		m_impulse *= maxImpulse / m_impulse.Length();
+	}
+	impulse = m_impulse - oldImpulse;
+
+	vB += m_invMassB * impulse;
+	wB += m_invIB * b2Cross(m_rB, impulse);
+
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+}
+
+bool b2MouseJoint::SolvePositionConstraints(const b2SolverData& data)
+{
+	B2_NOT_USED(data);
+	return true;
+}
+
+b2Vec2 b2MouseJoint::GetAnchorA() const
+{
+	return m_targetA;
+}
+
+b2Vec2 b2MouseJoint::GetAnchorB() const
+{
+	return m_bodyB->GetWorldPoint(m_localAnchorB);
+}
+
+b2Vec2 b2MouseJoint::GetReactionForce(float32 inv_dt) const
+{
+	return inv_dt * m_impulse;
+}
+
+float32 b2MouseJoint::GetReactionTorque(float32 inv_dt) const
+{
+	return inv_dt * 0.0f;
+}

modules/juce_box2d/box2d/Dynamics/Joints/b2MouseJoint.h

@@ -0,0 +1,126 @@
+/*
+* Copyright (c) 2006-2007 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#ifndef B2_MOUSE_JOINT_H
+#define B2_MOUSE_JOINT_H
+
+#include "b2Joint.h"
+
+/// Mouse joint definition. This requires a world target point,
+/// tuning parameters, and the time step.
+struct b2MouseJointDef : public b2JointDef
+{
+	b2MouseJointDef()
+	{
+		type = e_mouseJoint;
+		target.Set(0.0f, 0.0f);
+		maxForce = 0.0f;
+		frequencyHz = 5.0f;
+		dampingRatio = 0.7f;
+	}
+
+	/// The initial world target point. This is assumed
+	/// to coincide with the body anchor initially.
+	b2Vec2 target;
+
+	/// The maximum constraint force that can be exerted
+	/// to move the candidate body. Usually you will express
+	/// as some multiple of the weight (multiplier * mass * gravity).
+	float32 maxForce;
+
+	/// The response speed.
+	float32 frequencyHz;
+
+	/// The damping ratio. 0 = no damping, 1 = critical damping.
+	float32 dampingRatio;
+};
+
+/// A mouse joint is used to make a point on a body track a
+/// specified world point. This a soft constraint with a maximum
+/// force. This allows the constraint to stretch and without
+/// applying huge forces.
+/// NOTE: this joint is not documented in the manual because it was
+/// developed to be used in the testbed. If you want to learn how to
+/// use the mouse joint, look at the testbed.
+class b2MouseJoint : public b2Joint
+{
+public:
+
+	/// Implements b2Joint.
+	b2Vec2 GetAnchorA() const;
+
+	/// Implements b2Joint.
+	b2Vec2 GetAnchorB() const;
+
+	/// Implements b2Joint.
+	b2Vec2 GetReactionForce(float32 inv_dt) const;
+
+	/// Implements b2Joint.
+	float32 GetReactionTorque(float32 inv_dt) const;
+
+	/// Use this to update the target point.
+	void SetTarget(const b2Vec2& target);
+	const b2Vec2& GetTarget() const;
+
+	/// Set/get the maximum force in Newtons.
+	void SetMaxForce(float32 force);
+	float32 GetMaxForce() const;
+
+	/// Set/get the frequency in Hertz.
+	void SetFrequency(float32 hz);
+	float32 GetFrequency() const;
+
+	/// Set/get the damping ratio (dimensionless).
+	void SetDampingRatio(float32 ratio);
+	float32 GetDampingRatio() const;
+
+	/// The mouse joint does not support dumping.
+	void Dump() { b2Log("Mouse joint dumping is not supported.\n"); }
+
+protected:
+	friend class b2Joint;
+
+	b2MouseJoint(const b2MouseJointDef* def);
+
+	void InitVelocityConstraints(const b2SolverData& data);
+	void SolveVelocityConstraints(const b2SolverData& data);
+	bool SolvePositionConstraints(const b2SolverData& data);
+
+	b2Vec2 m_localAnchorB;
+	b2Vec2 m_targetA;
+	float32 m_frequencyHz;
+	float32 m_dampingRatio;
+	float32 m_beta;
+
+	// Solver shared
+	b2Vec2 m_impulse;
+	float32 m_maxForce;
+	float32 m_gamma;
+
+	// Solver temp
+	juce::int32 m_indexA;
+	juce::int32 m_indexB;
+	b2Vec2 m_rB;
+	b2Vec2 m_localCenterB;
+	float32 m_invMassB;
+	float32 m_invIB;
+	b2Mat22 m_mass;
+	b2Vec2 m_C;
+};
+
+#endif

modules/juce_box2d/box2d/Dynamics/Joints/b2PrismaticJoint.cpp

@@ -0,0 +1,635 @@
+/*
+* Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#include "b2PrismaticJoint.h"
+#include "../b2Body.h"
+#include "../b2TimeStep.h"
+
+// Linear constraint (point-to-line)
+// d = p2 - p1 = x2 + r2 - x1 - r1
+// C = dot(perp, d)
+// Cdot = dot(d, cross(w1, perp)) + dot(perp, v2 + cross(w2, r2) - v1 - cross(w1, r1))
+//      = -dot(perp, v1) - dot(cross(d + r1, perp), w1) + dot(perp, v2) + dot(cross(r2, perp), v2)
+// J = [-perp, -cross(d + r1, perp), perp, cross(r2,perp)]
+//
+// Angular constraint
+// C = a2 - a1 + a_initial
+// Cdot = w2 - w1
+// J = [0 0 -1 0 0 1]
+//
+// K = J * invM * JT
+//
+// J = [-a -s1 a s2]
+//     [0  -1  0  1]
+// a = perp
+// s1 = cross(d + r1, a) = cross(p2 - x1, a)
+// s2 = cross(r2, a) = cross(p2 - x2, a)
+
+
+// Motor/Limit linear constraint
+// C = dot(ax1, d)
+// Cdot = = -dot(ax1, v1) - dot(cross(d + r1, ax1), w1) + dot(ax1, v2) + dot(cross(r2, ax1), v2)
+// J = [-ax1 -cross(d+r1,ax1) ax1 cross(r2,ax1)]
+
+// Block Solver
+// We develop a block solver that includes the joint limit. This makes the limit stiff (inelastic) even
+// when the mass has poor distribution (leading to large torques about the joint anchor points).
+//
+// The Jacobian has 3 rows:
+// J = [-uT -s1 uT s2] // linear
+//     [0   -1   0  1] // angular
+//     [-vT -a1 vT a2] // limit
+//
+// u = perp
+// v = axis
+// s1 = cross(d + r1, u), s2 = cross(r2, u)
+// a1 = cross(d + r1, v), a2 = cross(r2, v)
+
+// M * (v2 - v1) = JT * df
+// J * v2 = bias
+//
+// v2 = v1 + invM * JT * df
+// J * (v1 + invM * JT * df) = bias
+// K * df = bias - J * v1 = -Cdot
+// K = J * invM * JT
+// Cdot = J * v1 - bias
+//
+// Now solve for f2.
+// df = f2 - f1
+// K * (f2 - f1) = -Cdot
+// f2 = invK * (-Cdot) + f1
+//
+// Clamp accumulated limit impulse.
+// lower: f2(3) = max(f2(3), 0)
+// upper: f2(3) = min(f2(3), 0)
+//
+// Solve for correct f2(1:2)
+// K(1:2, 1:2) * f2(1:2) = -Cdot(1:2) - K(1:2,3) * f2(3) + K(1:2,1:3) * f1
+//                       = -Cdot(1:2) - K(1:2,3) * f2(3) + K(1:2,1:2) * f1(1:2) + K(1:2,3) * f1(3)
+// K(1:2, 1:2) * f2(1:2) = -Cdot(1:2) - K(1:2,3) * (f2(3) - f1(3)) + K(1:2,1:2) * f1(1:2)
+// f2(1:2) = invK(1:2,1:2) * (-Cdot(1:2) - K(1:2,3) * (f2(3) - f1(3))) + f1(1:2)
+//
+// Now compute impulse to be applied:
+// df = f2 - f1
+
+void b2PrismaticJointDef::Initialize(b2Body* bA, b2Body* bB, const b2Vec2& anchor, const b2Vec2& axis)
+{
+	bodyA = bA;
+	bodyB = bB;
+	localAnchorA = bodyA->GetLocalPoint(anchor);
+	localAnchorB = bodyB->GetLocalPoint(anchor);
+	localAxisA = bodyA->GetLocalVector(axis);
+	referenceAngle = bodyB->GetAngle() - bodyA->GetAngle();
+}
+
+b2PrismaticJoint::b2PrismaticJoint(const b2PrismaticJointDef* def)
+: b2Joint(def)
+{
+	m_localAnchorA = def->localAnchorA;
+	m_localAnchorB = def->localAnchorB;
+	m_localXAxisA = def->localAxisA;
+	m_localXAxisA.Normalize();
+	m_localYAxisA = b2Cross(1.0f, m_localXAxisA);
+	m_referenceAngle = def->referenceAngle;
+
+	m_impulse.SetZero();
+	m_motorMass = 0.0f;
+	m_motorImpulse = 0.0f;
+
+	m_lowerTranslation = def->lowerTranslation;
+	m_upperTranslation = def->upperTranslation;
+	m_maxMotorForce = def->maxMotorForce;
+	m_motorSpeed = def->motorSpeed;
+	m_enableLimit = def->enableLimit;
+	m_enableMotor = def->enableMotor;
+	m_limitState = e_inactiveLimit;
+
+	m_axis.SetZero();
+	m_perp.SetZero();
+}
+
+void b2PrismaticJoint::InitVelocityConstraints(const b2SolverData& data)
+{
+	m_indexA = m_bodyA->m_islandIndex;
+	m_indexB = m_bodyB->m_islandIndex;
+	m_localCenterA = m_bodyA->m_sweep.localCenter;
+	m_localCenterB = m_bodyB->m_sweep.localCenter;
+	m_invMassA = m_bodyA->m_invMass;
+	m_invMassB = m_bodyB->m_invMass;
+	m_invIA = m_bodyA->m_invI;
+	m_invIB = m_bodyB->m_invI;
+
+	b2Vec2 cA = data.positions[m_indexA].c;
+	float32 aA = data.positions[m_indexA].a;
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float32 wA = data.velocities[m_indexA].w;
+
+	b2Vec2 cB = data.positions[m_indexB].c;
+	float32 aB = data.positions[m_indexB].a;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	b2Rot qA(aA), qB(aB);
+
+	// Compute the effective masses.
+	b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
+	b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
+	b2Vec2 d = (cB - cA) + rB - rA;
+
+	float32 mA = m_invMassA, mB = m_invMassB;
+	float32 iA = m_invIA, iB = m_invIB;
+
+	// Compute motor Jacobian and effective mass.
+	{
+		m_axis = b2Mul(qA, m_localXAxisA);
+		m_a1 = b2Cross(d + rA, m_axis);
+		m_a2 = b2Cross(rB, m_axis);
+
+		m_motorMass = mA + mB + iA * m_a1 * m_a1 + iB * m_a2 * m_a2;
+		if (m_motorMass > 0.0f)
+		{
+			m_motorMass = 1.0f / m_motorMass;
+		}
+	}
+
+	// Prismatic constraint.
+	{
+		m_perp = b2Mul(qA, m_localYAxisA);
+
+		m_s1 = b2Cross(d + rA, m_perp);
+		m_s2 = b2Cross(rB, m_perp);
+
+		float32 k11 = mA + mB + iA * m_s1 * m_s1 + iB * m_s2 * m_s2;
+		float32 k12 = iA * m_s1 + iB * m_s2;
+		float32 k13 = iA * m_s1 * m_a1 + iB * m_s2 * m_a2;
+		float32 k22 = iA + iB;
+		if (k22 == 0.0f)
+		{
+			// For bodies with fixed rotation.
+			k22 = 1.0f;
+		}
+		float32 k23 = iA * m_a1 + iB * m_a2;
+		float32 k33 = mA + mB + iA * m_a1 * m_a1 + iB * m_a2 * m_a2;
+
+		m_K.ex.Set(k11, k12, k13);
+		m_K.ey.Set(k12, k22, k23);
+		m_K.ez.Set(k13, k23, k33);
+	}
+
+	// Compute motor and limit terms.
+	if (m_enableLimit)
+	{
+		float32 jointTranslation = b2Dot(m_axis, d);
+		if (b2Abs(m_upperTranslation - m_lowerTranslation) < 2.0f * b2_linearSlop)
+		{
+			m_limitState = e_equalLimits;
+		}
+		else if (jointTranslation <= m_lowerTranslation)
+		{
+			if (m_limitState != e_atLowerLimit)
+			{
+				m_limitState = e_atLowerLimit;
+				m_impulse.z = 0.0f;
+			}
+		}
+		else if (jointTranslation >= m_upperTranslation)
+		{
+			if (m_limitState != e_atUpperLimit)
+			{
+				m_limitState = e_atUpperLimit;
+				m_impulse.z = 0.0f;
+			}
+		}
+		else
+		{
+			m_limitState = e_inactiveLimit;
+			m_impulse.z = 0.0f;
+		}
+	}
+	else
+	{
+		m_limitState = e_inactiveLimit;
+		m_impulse.z = 0.0f;
+	}
+
+	if (m_enableMotor == false)
+	{
+		m_motorImpulse = 0.0f;
+	}
+
+	if (data.step.warmStarting)
+	{
+		// Account for variable time step.
+		m_impulse *= data.step.dtRatio;
+		m_motorImpulse *= data.step.dtRatio;
+
+		b2Vec2 P = m_impulse.x * m_perp + (m_motorImpulse + m_impulse.z) * m_axis;
+		float32 LA = m_impulse.x * m_s1 + m_impulse.y + (m_motorImpulse + m_impulse.z) * m_a1;
+		float32 LB = m_impulse.x * m_s2 + m_impulse.y + (m_motorImpulse + m_impulse.z) * m_a2;
+
+		vA -= mA * P;
+		wA -= iA * LA;
+
+		vB += mB * P;
+		wB += iB * LB;
+	}
+	else
+	{
+		m_impulse.SetZero();
+		m_motorImpulse = 0.0f;
+	}
+
+	data.velocities[m_indexA].v = vA;
+	data.velocities[m_indexA].w = wA;
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+}
+
+void b2PrismaticJoint::SolveVelocityConstraints(const b2SolverData& data)
+{
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float32 wA = data.velocities[m_indexA].w;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	float32 mA = m_invMassA, mB = m_invMassB;
+	float32 iA = m_invIA, iB = m_invIB;
+
+	// Solve linear motor constraint.
+	if (m_enableMotor && m_limitState != e_equalLimits)
+	{
+		float32 Cdot = b2Dot(m_axis, vB - vA) + m_a2 * wB - m_a1 * wA;
+		float32 impulse = m_motorMass * (m_motorSpeed - Cdot);
+		float32 oldImpulse = m_motorImpulse;
+		float32 maxImpulse = data.step.dt * m_maxMotorForce;
+		m_motorImpulse = b2Clamp(m_motorImpulse + impulse, -maxImpulse, maxImpulse);
+		impulse = m_motorImpulse - oldImpulse;
+
+		b2Vec2 P = impulse * m_axis;
+		float32 LA = impulse * m_a1;
+		float32 LB = impulse * m_a2;
+
+		vA -= mA * P;
+		wA -= iA * LA;
+
+		vB += mB * P;
+		wB += iB * LB;
+	}
+
+	b2Vec2 Cdot1;
+	Cdot1.x = b2Dot(m_perp, vB - vA) + m_s2 * wB - m_s1 * wA;
+	Cdot1.y = wB - wA;
+
+	if (m_enableLimit && m_limitState != e_inactiveLimit)
+	{
+		// Solve prismatic and limit constraint in block form.
+		float32 Cdot2;
+		Cdot2 = b2Dot(m_axis, vB - vA) + m_a2 * wB - m_a1 * wA;
+		b2Vec3 Cdot(Cdot1.x, Cdot1.y, Cdot2);
+
+		b2Vec3 f1 = m_impulse;
+		b2Vec3 df =  m_K.Solve33(-Cdot);
+		m_impulse += df;
+
+		if (m_limitState == e_atLowerLimit)
+		{
+			m_impulse.z = b2Max(m_impulse.z, 0.0f);
+		}
+		else if (m_limitState == e_atUpperLimit)
+		{
+			m_impulse.z = b2Min(m_impulse.z, 0.0f);
+		}
+
+		// f2(1:2) = invK(1:2,1:2) * (-Cdot(1:2) - K(1:2,3) * (f2(3) - f1(3))) + f1(1:2)
+		b2Vec2 b = -Cdot1 - (m_impulse.z - f1.z) * b2Vec2(m_K.ez.x, m_K.ez.y);
+		b2Vec2 f2r = m_K.Solve22(b) + b2Vec2(f1.x, f1.y);
+		m_impulse.x = f2r.x;
+		m_impulse.y = f2r.y;
+
+		df = m_impulse - f1;
+
+		b2Vec2 P = df.x * m_perp + df.z * m_axis;
+		float32 LA = df.x * m_s1 + df.y + df.z * m_a1;
+		float32 LB = df.x * m_s2 + df.y + df.z * m_a2;
+
+		vA -= mA * P;
+		wA -= iA * LA;
+
+		vB += mB * P;
+		wB += iB * LB;
+	}
+	else
+	{
+		// Limit is inactive, just solve the prismatic constraint in block form.
+		b2Vec2 df = m_K.Solve22(-Cdot1);
+		m_impulse.x += df.x;
+		m_impulse.y += df.y;
+
+		b2Vec2 P = df.x * m_perp;
+		float32 LA = df.x * m_s1 + df.y;
+		float32 LB = df.x * m_s2 + df.y;
+
+		vA -= mA * P;
+		wA -= iA * LA;
+
+		vB += mB * P;
+		wB += iB * LB;
+
+		Cdot1.x = b2Dot(m_perp, vB - vA) + m_s2 * wB - m_s1 * wA;
+		Cdot1.y = wB - wA;
+
+		/*if (b2Abs(Cdot1.x) > 0.01f || b2Abs(Cdot1.y) > 0.01f)
+		{
+			b2Vec2 test = b2Mul22(m_K, df);
+			Cdot1.x += 0.0f;
+		}*/
+	}
+
+	data.velocities[m_indexA].v = vA;
+	data.velocities[m_indexA].w = wA;
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+}
+
+bool b2PrismaticJoint::SolvePositionConstraints(const b2SolverData& data)
+{
+	b2Vec2 cA = data.positions[m_indexA].c;
+	float32 aA = data.positions[m_indexA].a;
+	b2Vec2 cB = data.positions[m_indexB].c;
+	float32 aB = data.positions[m_indexB].a;
+
+	b2Rot qA(aA), qB(aB);
+
+	float32 mA = m_invMassA, mB = m_invMassB;
+	float32 iA = m_invIA, iB = m_invIB;
+
+	// Compute fresh Jacobians
+	b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
+	b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
+	b2Vec2 d = cB + rB - cA - rA;
+
+	b2Vec2 axis = b2Mul(qA, m_localXAxisA);
+	float32 a1 = b2Cross(d + rA, axis);
+	float32 a2 = b2Cross(rB, axis);
+	b2Vec2 perp = b2Mul(qA, m_localYAxisA);
+
+	float32 s1 = b2Cross(d + rA, perp);
+	float32 s2 = b2Cross(rB, perp);
+
+	b2Vec3 impulse;
+	b2Vec2 C1;
+	C1.x = b2Dot(perp, d);
+	C1.y = aB - aA - m_referenceAngle;
+
+	float32 linearError = b2Abs(C1.x);
+	float32 angularError = b2Abs(C1.y);
+
+	bool active = false;
+	float32 C2 = 0.0f;
+	if (m_enableLimit)
+	{
+		float32 translation = b2Dot(axis, d);
+		if (b2Abs(m_upperTranslation - m_lowerTranslation) < 2.0f * b2_linearSlop)
+		{
+			// Prevent large angular corrections
+			C2 = b2Clamp(translation, -b2_maxLinearCorrection, b2_maxLinearCorrection);
+			linearError = b2Max(linearError, b2Abs(translation));
+			active = true;
+		}
+		else if (translation <= m_lowerTranslation)
+		{
+			// Prevent large linear corrections and allow some slop.
+			C2 = b2Clamp(translation - m_lowerTranslation + b2_linearSlop, -b2_maxLinearCorrection, 0.0f);
+			linearError = b2Max(linearError, m_lowerTranslation - translation);
+			active = true;
+		}
+		else if (translation >= m_upperTranslation)
+		{
+			// Prevent large linear corrections and allow some slop.
+			C2 = b2Clamp(translation - m_upperTranslation - b2_linearSlop, 0.0f, b2_maxLinearCorrection);
+			linearError = b2Max(linearError, translation - m_upperTranslation);
+			active = true;
+		}
+	}
+
+	if (active)
+	{
+		float32 k11 = mA + mB + iA * s1 * s1 + iB * s2 * s2;
+		float32 k12 = iA * s1 + iB * s2;
+		float32 k13 = iA * s1 * a1 + iB * s2 * a2;
+		float32 k22 = iA + iB;
+		if (k22 == 0.0f)
+		{
+			// For fixed rotation
+			k22 = 1.0f;
+		}
+		float32 k23 = iA * a1 + iB * a2;
+		float32 k33 = mA + mB + iA * a1 * a1 + iB * a2 * a2;
+
+		b2Mat33 K;
+		K.ex.Set(k11, k12, k13);
+		K.ey.Set(k12, k22, k23);
+		K.ez.Set(k13, k23, k33);
+
+		b2Vec3 C;
+		C.x = C1.x;
+		C.y = C1.y;
+		C.z = C2;
+
+		impulse = K.Solve33(-C);
+	}
+	else
+	{
+		float32 k11 = mA + mB + iA * s1 * s1 + iB * s2 * s2;
+		float32 k12 = iA * s1 + iB * s2;
+		float32 k22 = iA + iB;
+		if (k22 == 0.0f)
+		{
+			k22 = 1.0f;
+		}
+
+		b2Mat22 K;
+		K.ex.Set(k11, k12);
+		K.ey.Set(k12, k22);
+
+		b2Vec2 impulse1 = K.Solve(-C1);
+		impulse.x = impulse1.x;
+		impulse.y = impulse1.y;
+		impulse.z = 0.0f;
+	}
+
+	b2Vec2 P = impulse.x * perp + impulse.z * axis;
+	float32 LA = impulse.x * s1 + impulse.y + impulse.z * a1;
+	float32 LB = impulse.x * s2 + impulse.y + impulse.z * a2;
+
+	cA -= mA * P;
+	aA -= iA * LA;
+	cB += mB * P;
+	aB += iB * LB;
+
+	data.positions[m_indexA].c = cA;
+	data.positions[m_indexA].a = aA;
+	data.positions[m_indexB].c = cB;
+	data.positions[m_indexB].a = aB;
+
+	return linearError <= b2_linearSlop && angularError <= b2_angularSlop;
+}
+
+b2Vec2 b2PrismaticJoint::GetAnchorA() const
+{
+	return m_bodyA->GetWorldPoint(m_localAnchorA);
+}
+
+b2Vec2 b2PrismaticJoint::GetAnchorB() const
+{
+	return m_bodyB->GetWorldPoint(m_localAnchorB);
+}
+
+b2Vec2 b2PrismaticJoint::GetReactionForce(float32 inv_dt) const
+{
+	return inv_dt * (m_impulse.x * m_perp + (m_motorImpulse + m_impulse.z) * m_axis);
+}
+
+float32 b2PrismaticJoint::GetReactionTorque(float32 inv_dt) const
+{
+	return inv_dt * m_impulse.y;
+}
+
+float32 b2PrismaticJoint::GetJointTranslation() const
+{
+	b2Vec2 pA = m_bodyA->GetWorldPoint(m_localAnchorA);
+	b2Vec2 pB = m_bodyB->GetWorldPoint(m_localAnchorB);
+	b2Vec2 d = pB - pA;
+	b2Vec2 axis = m_bodyA->GetWorldVector(m_localXAxisA);
+
+	float32 translation = b2Dot(d, axis);
+	return translation;
+}
+
+float32 b2PrismaticJoint::GetJointSpeed() const
+{
+	b2Body* bA = m_bodyA;
+	b2Body* bB = m_bodyB;
+
+	b2Vec2 rA = b2Mul(bA->m_xf.q, m_localAnchorA - bA->m_sweep.localCenter);
+	b2Vec2 rB = b2Mul(bB->m_xf.q, m_localAnchorB - bB->m_sweep.localCenter);
+	b2Vec2 p1 = bA->m_sweep.c + rA;
+	b2Vec2 p2 = bB->m_sweep.c + rB;
+	b2Vec2 d = p2 - p1;
+	b2Vec2 axis = b2Mul(bA->m_xf.q, m_localXAxisA);
+
+	b2Vec2 vA = bA->m_linearVelocity;
+	b2Vec2 vB = bB->m_linearVelocity;
+	float32 wA = bA->m_angularVelocity;
+	float32 wB = bB->m_angularVelocity;
+
+	float32 speed = b2Dot(d, b2Cross(wA, axis)) + b2Dot(axis, vB + b2Cross(wB, rB) - vA - b2Cross(wA, rA));
+	return speed;
+}
+
+bool b2PrismaticJoint::IsLimitEnabled() const
+{
+	return m_enableLimit;
+}
+
+void b2PrismaticJoint::EnableLimit(bool flag)
+{
+	if (flag != m_enableLimit)
+	{
+		m_bodyA->SetAwake(true);
+		m_bodyB->SetAwake(true);
+		m_enableLimit = flag;
+		m_impulse.z = 0.0f;
+	}
+}
+
+float32 b2PrismaticJoint::GetLowerLimit() const
+{
+	return m_lowerTranslation;
+}
+
+float32 b2PrismaticJoint::GetUpperLimit() const
+{
+	return m_upperTranslation;
+}
+
+void b2PrismaticJoint::SetLimits(float32 lower, float32 upper)
+{
+	b2Assert(lower <= upper);
+	if (lower != m_lowerTranslation || upper != m_upperTranslation)
+	{
+		m_bodyA->SetAwake(true);
+		m_bodyB->SetAwake(true);
+		m_lowerTranslation = lower;
+		m_upperTranslation = upper;
+		m_impulse.z = 0.0f;
+	}
+}
+
+bool b2PrismaticJoint::IsMotorEnabled() const
+{
+	return m_enableMotor;
+}
+
+void b2PrismaticJoint::EnableMotor(bool flag)
+{
+	m_bodyA->SetAwake(true);
+	m_bodyB->SetAwake(true);
+	m_enableMotor = flag;
+}
+
+void b2PrismaticJoint::SetMotorSpeed(float32 speed)
+{
+	m_bodyA->SetAwake(true);
+	m_bodyB->SetAwake(true);
+	m_motorSpeed = speed;
+}
+
+void b2PrismaticJoint::SetMaxMotorForce(float32 force)
+{
+	m_bodyA->SetAwake(true);
+	m_bodyB->SetAwake(true);
+	m_maxMotorForce = force;
+}
+
+float32 b2PrismaticJoint::GetMotorForce(float32 inv_dt) const
+{
+	return inv_dt * m_motorImpulse;
+}
+
+void b2PrismaticJoint::Dump()
+{
+	int32 indexA = m_bodyA->m_islandIndex;
+	int32 indexB = m_bodyB->m_islandIndex;
+
+	b2Log("  b2PrismaticJointDef jd;\n");
+	b2Log("  jd.bodyA = bodies[%d];\n", indexA);
+	b2Log("  jd.bodyB = bodies[%d];\n", indexB);
+	b2Log("  jd.collideConnected = bool(%d);\n", m_collideConnected);
+	b2Log("  jd.localAnchorA.Set(%.15lef, %.15lef);\n", m_localAnchorA.x, m_localAnchorA.y);
+	b2Log("  jd.localAnchorB.Set(%.15lef, %.15lef);\n", m_localAnchorB.x, m_localAnchorB.y);
+	b2Log("  jd.localAxisA.Set(%.15lef, %.15lef);\n", m_localXAxisA.x, m_localXAxisA.y);
+	b2Log("  jd.referenceAngle = %.15lef;\n", m_referenceAngle);
+	b2Log("  jd.enableLimit = bool(%d);\n", m_enableLimit);
+	b2Log("  jd.lowerTranslation = %.15lef;\n", m_lowerTranslation);
+	b2Log("  jd.upperTranslation = %.15lef;\n", m_upperTranslation);
+	b2Log("  jd.enableMotor = bool(%d);\n", m_enableMotor);
+	b2Log("  jd.motorSpeed = %.15lef;\n", m_motorSpeed);
+	b2Log("  jd.maxMotorForce = %.15lef;\n", m_maxMotorForce);
+	b2Log("  joints[%d] = m_world->CreateJoint(&jd);\n", m_index);
+}

modules/juce_box2d/box2d/Dynamics/Joints/b2PrismaticJoint.h

@@ -0,0 +1,196 @@
+/*
+* Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#ifndef B2_PRISMATIC_JOINT_H
+#define B2_PRISMATIC_JOINT_H
+
+#include "b2Joint.h"
+
+/// Prismatic joint definition. This requires defining a line of
+/// motion using an axis and an anchor point. The definition uses local
+/// anchor points and a local axis so that the initial configuration
+/// can violate the constraint slightly. The joint translation is zero
+/// when the local anchor points coincide in world space. Using local
+/// anchors and a local axis helps when saving and loading a game.
+struct b2PrismaticJointDef : public b2JointDef
+{
+	b2PrismaticJointDef()
+	{
+		type = e_prismaticJoint;
+		localAnchorA.SetZero();
+		localAnchorB.SetZero();
+		localAxisA.Set(1.0f, 0.0f);
+		referenceAngle = 0.0f;
+		enableLimit = false;
+		lowerTranslation = 0.0f;
+		upperTranslation = 0.0f;
+		enableMotor = false;
+		maxMotorForce = 0.0f;
+		motorSpeed = 0.0f;
+	}
+
+	/// Initialize the bodies, anchors, axis, and reference angle using the world
+	/// anchor and unit world axis.
+	void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor, const b2Vec2& axis);
+
+	/// The local anchor point relative to bodyA's origin.
+	b2Vec2 localAnchorA;
+
+	/// The local anchor point relative to bodyB's origin.
+	b2Vec2 localAnchorB;
+
+	/// The local translation unit axis in bodyA.
+	b2Vec2 localAxisA;
+
+	/// The constrained angle between the bodies: bodyB_angle - bodyA_angle.
+	float32 referenceAngle;
+
+	/// Enable/disable the joint limit.
+	bool enableLimit;
+
+	/// The lower translation limit, usually in meters.
+	float32 lowerTranslation;
+
+	/// The upper translation limit, usually in meters.
+	float32 upperTranslation;
+
+	/// Enable/disable the joint motor.
+	bool enableMotor;
+
+	/// The maximum motor torque, usually in N-m.
+	float32 maxMotorForce;
+
+	/// The desired motor speed in radians per second.
+	float32 motorSpeed;
+};
+
+/// A prismatic joint. This joint provides one degree of freedom: translation
+/// along an axis fixed in bodyA. Relative rotation is prevented. You can
+/// use a joint limit to restrict the range of motion and a joint motor to
+/// drive the motion or to model joint friction.
+class b2PrismaticJoint : public b2Joint
+{
+public:
+	b2Vec2 GetAnchorA() const;
+	b2Vec2 GetAnchorB() const;
+
+	b2Vec2 GetReactionForce(float32 inv_dt) const;
+	float32 GetReactionTorque(float32 inv_dt) const;
+
+	/// The local anchor point relative to bodyA's origin.
+	const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }
+
+	/// The local anchor point relative to bodyB's origin.
+	const b2Vec2& GetLocalAnchorB() const  { return m_localAnchorB; }
+
+	/// The local joint axis relative to bodyA.
+	const b2Vec2& GetLocalAxisA() const { return m_localXAxisA; }
+
+	/// Get the reference angle.
+	float32 GetReferenceAngle() const { return m_referenceAngle; }
+
+	/// Get the current joint translation, usually in meters.
+	float32 GetJointTranslation() const;
+
+	/// Get the current joint translation speed, usually in meters per second.
+	float32 GetJointSpeed() const;
+
+	/// Is the joint limit enabled?
+	bool IsLimitEnabled() const;
+
+	/// Enable/disable the joint limit.
+	void EnableLimit(bool flag);
+
+	/// Get the lower joint limit, usually in meters.
+	float32 GetLowerLimit() const;
+
+	/// Get the upper joint limit, usually in meters.
+	float32 GetUpperLimit() const;
+
+	/// Set the joint limits, usually in meters.
+	void SetLimits(float32 lower, float32 upper);
+
+	/// Is the joint motor enabled?
+	bool IsMotorEnabled() const;
+
+	/// Enable/disable the joint motor.
+	void EnableMotor(bool flag);
+
+	/// Set the motor speed, usually in meters per second.
+	void SetMotorSpeed(float32 speed);
+
+	/// Get the motor speed, usually in meters per second.
+	float32 GetMotorSpeed() const;
+
+	/// Set the maximum motor force, usually in N.
+	void SetMaxMotorForce(float32 force);
+	float32 GetMaxMotorForce() const { return m_maxMotorForce; }
+
+	/// Get the current motor force given the inverse time step, usually in N.
+	float32 GetMotorForce(float32 inv_dt) const;
+
+	/// Dump to b2Log
+	void Dump();
+
+protected:
+	friend class b2Joint;
+	friend class b2GearJoint;
+	b2PrismaticJoint(const b2PrismaticJointDef* def);
+
+	void InitVelocityConstraints(const b2SolverData& data);
+	void SolveVelocityConstraints(const b2SolverData& data);
+	bool SolvePositionConstraints(const b2SolverData& data);
+
+	// Solver shared
+	b2Vec2 m_localAnchorA;
+	b2Vec2 m_localAnchorB;
+	b2Vec2 m_localXAxisA;
+	b2Vec2 m_localYAxisA;
+	float32 m_referenceAngle;
+	b2Vec3 m_impulse;
+	float32 m_motorImpulse;
+	float32 m_lowerTranslation;
+	float32 m_upperTranslation;
+	float32 m_maxMotorForce;
+	float32 m_motorSpeed;
+	bool m_enableLimit;
+	bool m_enableMotor;
+	b2LimitState m_limitState;
+
+	// Solver temp
+	juce::int32 m_indexA;
+	juce::int32 m_indexB;
+	b2Vec2 m_localCenterA;
+	b2Vec2 m_localCenterB;
+	float32 m_invMassA;
+	float32 m_invMassB;
+	float32 m_invIA;
+	float32 m_invIB;
+	b2Vec2 m_axis, m_perp;
+	float32 m_s1, m_s2;
+	float32 m_a1, m_a2;
+	b2Mat33 m_K;
+	float32 m_motorMass;
+};
+
+inline float32 b2PrismaticJoint::GetMotorSpeed() const
+{
+	return m_motorSpeed;
+}
+
+#endif

modules/juce_box2d/box2d/Dynamics/Joints/b2PulleyJoint.cpp

@@ -0,0 +1,332 @@
+/*
+* Copyright (c) 2007 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#include "b2PulleyJoint.h"
+#include "../b2Body.h"
+#include "../b2TimeStep.h"
+
+// Pulley:
+// length1 = norm(p1 - s1)
+// length2 = norm(p2 - s2)
+// C0 = (length1 + ratio * length2)_initial
+// C = C0 - (length1 + ratio * length2)
+// u1 = (p1 - s1) / norm(p1 - s1)
+// u2 = (p2 - s2) / norm(p2 - s2)
+// Cdot = -dot(u1, v1 + cross(w1, r1)) - ratio * dot(u2, v2 + cross(w2, r2))
+// J = -[u1 cross(r1, u1) ratio * u2  ratio * cross(r2, u2)]
+// K = J * invM * JT
+//   = invMass1 + invI1 * cross(r1, u1)^2 + ratio^2 * (invMass2 + invI2 * cross(r2, u2)^2)
+
+void b2PulleyJointDef::Initialize(b2Body* bA, b2Body* bB,
+				const b2Vec2& groundA, const b2Vec2& groundB,
+				const b2Vec2& anchorA, const b2Vec2& anchorB,
+				float32 r)
+{
+	bodyA = bA;
+	bodyB = bB;
+	groundAnchorA = groundA;
+	groundAnchorB = groundB;
+	localAnchorA = bodyA->GetLocalPoint(anchorA);
+	localAnchorB = bodyB->GetLocalPoint(anchorB);
+	b2Vec2 dA = anchorA - groundA;
+	lengthA = dA.Length();
+	b2Vec2 dB = anchorB - groundB;
+	lengthB = dB.Length();
+	ratio = r;
+	b2Assert(ratio > b2_epsilon);
+}
+
+b2PulleyJoint::b2PulleyJoint(const b2PulleyJointDef* def)
+: b2Joint(def)
+{
+	m_groundAnchorA = def->groundAnchorA;
+	m_groundAnchorB = def->groundAnchorB;
+	m_localAnchorA = def->localAnchorA;
+	m_localAnchorB = def->localAnchorB;
+
+	m_lengthA = def->lengthA;
+	m_lengthB = def->lengthB;
+
+	b2Assert(def->ratio != 0.0f);
+	m_ratio = def->ratio;
+
+	m_constant = def->lengthA + m_ratio * def->lengthB;
+
+	m_impulse = 0.0f;
+}
+
+void b2PulleyJoint::InitVelocityConstraints(const b2SolverData& data)
+{
+	m_indexA = m_bodyA->m_islandIndex;
+	m_indexB = m_bodyB->m_islandIndex;
+	m_localCenterA = m_bodyA->m_sweep.localCenter;
+	m_localCenterB = m_bodyB->m_sweep.localCenter;
+	m_invMassA = m_bodyA->m_invMass;
+	m_invMassB = m_bodyB->m_invMass;
+	m_invIA = m_bodyA->m_invI;
+	m_invIB = m_bodyB->m_invI;
+
+	b2Vec2 cA = data.positions[m_indexA].c;
+	float32 aA = data.positions[m_indexA].a;
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float32 wA = data.velocities[m_indexA].w;
+
+	b2Vec2 cB = data.positions[m_indexB].c;
+	float32 aB = data.positions[m_indexB].a;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	b2Rot qA(aA), qB(aB);
+
+	m_rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
+	m_rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
+
+	// Get the pulley axes.
+	m_uA = cA + m_rA - m_groundAnchorA;
+	m_uB = cB + m_rB - m_groundAnchorB;
+
+	float32 lengthA = m_uA.Length();
+	float32 lengthB = m_uB.Length();
+
+	if (lengthA > 10.0f * b2_linearSlop)
+	{
+		m_uA *= 1.0f / lengthA;
+	}
+	else
+	{
+		m_uA.SetZero();
+	}
+
+	if (lengthB > 10.0f * b2_linearSlop)
+	{
+		m_uB *= 1.0f / lengthB;
+	}
+	else
+	{
+		m_uB.SetZero();
+	}
+
+	// Compute effective mass.
+	float32 ruA = b2Cross(m_rA, m_uA);
+	float32 ruB = b2Cross(m_rB, m_uB);
+
+	float32 mA = m_invMassA + m_invIA * ruA * ruA;
+	float32 mB = m_invMassB + m_invIB * ruB * ruB;
+
+	m_mass = mA + m_ratio * m_ratio * mB;
+
+	if (m_mass > 0.0f)
+	{
+		m_mass = 1.0f / m_mass;
+	}
+
+	if (data.step.warmStarting)
+	{
+		// Scale impulses to support variable time steps.
+		m_impulse *= data.step.dtRatio;
+
+		// Warm starting.
+		b2Vec2 PA = -(m_impulse) * m_uA;
+		b2Vec2 PB = (-m_ratio * m_impulse) * m_uB;
+
+		vA += m_invMassA * PA;
+		wA += m_invIA * b2Cross(m_rA, PA);
+		vB += m_invMassB * PB;
+		wB += m_invIB * b2Cross(m_rB, PB);
+	}
+	else
+	{
+		m_impulse = 0.0f;
+	}
+
+	data.velocities[m_indexA].v = vA;
+	data.velocities[m_indexA].w = wA;
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+}
+
+void b2PulleyJoint::SolveVelocityConstraints(const b2SolverData& data)
+{
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float32 wA = data.velocities[m_indexA].w;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	b2Vec2 vpA = vA + b2Cross(wA, m_rA);
+	b2Vec2 vpB = vB + b2Cross(wB, m_rB);
+
+	float32 Cdot = -b2Dot(m_uA, vpA) - m_ratio * b2Dot(m_uB, vpB);
+	float32 impulse = -m_mass * Cdot;
+	m_impulse += impulse;
+
+	b2Vec2 PA = -impulse * m_uA;
+	b2Vec2 PB = -m_ratio * impulse * m_uB;
+	vA += m_invMassA * PA;
+	wA += m_invIA * b2Cross(m_rA, PA);
+	vB += m_invMassB * PB;
+	wB += m_invIB * b2Cross(m_rB, PB);
+
+	data.velocities[m_indexA].v = vA;
+	data.velocities[m_indexA].w = wA;
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+}
+
+bool b2PulleyJoint::SolvePositionConstraints(const b2SolverData& data)
+{
+	b2Vec2 cA = data.positions[m_indexA].c;
+	float32 aA = data.positions[m_indexA].a;
+	b2Vec2 cB = data.positions[m_indexB].c;
+	float32 aB = data.positions[m_indexB].a;
+
+	b2Rot qA(aA), qB(aB);
+
+	b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
+	b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
+
+	// Get the pulley axes.
+	b2Vec2 uA = cA + rA - m_groundAnchorA;
+	b2Vec2 uB = cB + rB - m_groundAnchorB;
+
+	float32 lengthA = uA.Length();
+	float32 lengthB = uB.Length();
+
+	if (lengthA > 10.0f * b2_linearSlop)
+	{
+		uA *= 1.0f / lengthA;
+	}
+	else
+	{
+		uA.SetZero();
+	}
+
+	if (lengthB > 10.0f * b2_linearSlop)
+	{
+		uB *= 1.0f / lengthB;
+	}
+	else
+	{
+		uB.SetZero();
+	}
+
+	// Compute effective mass.
+	float32 ruA = b2Cross(rA, uA);
+	float32 ruB = b2Cross(rB, uB);
+
+	float32 mA = m_invMassA + m_invIA * ruA * ruA;
+	float32 mB = m_invMassB + m_invIB * ruB * ruB;
+
+	float32 mass = mA + m_ratio * m_ratio * mB;
+
+	if (mass > 0.0f)
+	{
+		mass = 1.0f / mass;
+	}
+
+	float32 C = m_constant - lengthA - m_ratio * lengthB;
+	float32 linearError = b2Abs(C);
+
+	float32 impulse = -mass * C;
+
+	b2Vec2 PA = -impulse * uA;
+	b2Vec2 PB = -m_ratio * impulse * uB;
+
+	cA += m_invMassA * PA;
+	aA += m_invIA * b2Cross(rA, PA);
+	cB += m_invMassB * PB;
+	aB += m_invIB * b2Cross(rB, PB);
+
+	data.positions[m_indexA].c = cA;
+	data.positions[m_indexA].a = aA;
+	data.positions[m_indexB].c = cB;
+	data.positions[m_indexB].a = aB;
+
+	return linearError < b2_linearSlop;
+}
+
+b2Vec2 b2PulleyJoint::GetAnchorA() const
+{
+	return m_bodyA->GetWorldPoint(m_localAnchorA);
+}
+
+b2Vec2 b2PulleyJoint::GetAnchorB() const
+{
+	return m_bodyB->GetWorldPoint(m_localAnchorB);
+}
+
+b2Vec2 b2PulleyJoint::GetReactionForce(float32 inv_dt) const
+{
+	b2Vec2 P = m_impulse * m_uB;
+	return inv_dt * P;
+}
+
+float32 b2PulleyJoint::GetReactionTorque(float32 inv_dt) const
+{
+	B2_NOT_USED(inv_dt);
+	return 0.0f;
+}
+
+b2Vec2 b2PulleyJoint::GetGroundAnchorA() const
+{
+	return m_groundAnchorA;
+}
+
+b2Vec2 b2PulleyJoint::GetGroundAnchorB() const
+{
+	return m_groundAnchorB;
+}
+
+float32 b2PulleyJoint::GetLengthA() const
+{
+	b2Vec2 p = m_bodyA->GetWorldPoint(m_localAnchorA);
+	b2Vec2 s = m_groundAnchorA;
+	b2Vec2 d = p - s;
+	return d.Length();
+}
+
+float32 b2PulleyJoint::GetLengthB() const
+{
+	b2Vec2 p = m_bodyB->GetWorldPoint(m_localAnchorB);
+	b2Vec2 s = m_groundAnchorB;
+	b2Vec2 d = p - s;
+	return d.Length();
+}
+
+float32 b2PulleyJoint::GetRatio() const
+{
+	return m_ratio;
+}
+
+void b2PulleyJoint::Dump()
+{
+	int32 indexA = m_bodyA->m_islandIndex;
+	int32 indexB = m_bodyB->m_islandIndex;
+
+	b2Log("  b2PulleyJointDef jd;\n");
+	b2Log("  jd.bodyA = bodies[%d];\n", indexA);
+	b2Log("  jd.bodyB = bodies[%d];\n", indexB);
+	b2Log("  jd.collideConnected = bool(%d);\n", m_collideConnected);
+	b2Log("  jd.groundAnchorA.Set(%.15lef, %.15lef);\n", m_groundAnchorA.x, m_groundAnchorA.y);
+	b2Log("  jd.groundAnchorB.Set(%.15lef, %.15lef);\n", m_groundAnchorB.x, m_groundAnchorB.y);
+	b2Log("  jd.localAnchorA.Set(%.15lef, %.15lef);\n", m_localAnchorA.x, m_localAnchorA.y);
+	b2Log("  jd.localAnchorB.Set(%.15lef, %.15lef);\n", m_localAnchorB.x, m_localAnchorB.y);
+	b2Log("  jd.lengthA = %.15lef;\n", m_lengthA);
+	b2Log("  jd.lengthB = %.15lef;\n", m_lengthB);
+	b2Log("  jd.ratio = %.15lef;\n", m_ratio);
+	b2Log("  joints[%d] = m_world->CreateJoint(&jd);\n", m_index);
+}

modules/juce_box2d/box2d/Dynamics/Joints/b2PulleyJoint.h

@@ -0,0 +1,143 @@
+/*
+* Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#ifndef B2_PULLEY_JOINT_H
+#define B2_PULLEY_JOINT_H
+
+#include "b2Joint.h"
+
+const float32 b2_minPulleyLength = 2.0f;
+
+/// Pulley joint definition. This requires two ground anchors,
+/// two dynamic body anchor points, and a pulley ratio.
+struct b2PulleyJointDef : public b2JointDef
+{
+	b2PulleyJointDef()
+	{
+		type = e_pulleyJoint;
+		groundAnchorA.Set(-1.0f, 1.0f);
+		groundAnchorB.Set(1.0f, 1.0f);
+		localAnchorA.Set(-1.0f, 0.0f);
+		localAnchorB.Set(1.0f, 0.0f);
+		lengthA = 0.0f;
+		lengthB = 0.0f;
+		ratio = 1.0f;
+		collideConnected = true;
+	}
+
+	/// Initialize the bodies, anchors, lengths, max lengths, and ratio using the world anchors.
+	void Initialize(b2Body* bodyA, b2Body* bodyB,
+					const b2Vec2& groundAnchorA, const b2Vec2& groundAnchorB,
+					const b2Vec2& anchorA, const b2Vec2& anchorB,
+					float32 ratio);
+
+	/// The first ground anchor in world coordinates. This point never moves.
+	b2Vec2 groundAnchorA;
+
+	/// The second ground anchor in world coordinates. This point never moves.
+	b2Vec2 groundAnchorB;
+
+	/// The local anchor point relative to bodyA's origin.
+	b2Vec2 localAnchorA;
+
+	/// The local anchor point relative to bodyB's origin.
+	b2Vec2 localAnchorB;
+
+	/// The a reference length for the segment attached to bodyA.
+	float32 lengthA;
+
+	/// The a reference length for the segment attached to bodyB.
+	float32 lengthB;
+
+	/// The pulley ratio, used to simulate a block-and-tackle.
+	float32 ratio;
+};
+
+/// The pulley joint is connected to two bodies and two fixed ground points.
+/// The pulley supports a ratio such that:
+/// length1 + ratio * length2 <= constant
+/// Yes, the force transmitted is scaled by the ratio.
+/// Warning: the pulley joint can get a bit squirrelly by itself. They often
+/// work better when combined with prismatic joints. You should also cover the
+/// the anchor points with static shapes to prevent one side from going to
+/// zero length.
+class b2PulleyJoint : public b2Joint
+{
+public:
+	b2Vec2 GetAnchorA() const;
+	b2Vec2 GetAnchorB() const;
+
+	b2Vec2 GetReactionForce(float32 inv_dt) const;
+	float32 GetReactionTorque(float32 inv_dt) const;
+
+	/// Get the first ground anchor.
+	b2Vec2 GetGroundAnchorA() const;
+
+	/// Get the second ground anchor.
+	b2Vec2 GetGroundAnchorB() const;
+
+	/// Get the current length of the segment attached to bodyA.
+	float32 GetLengthA() const;
+
+	/// Get the current length of the segment attached to bodyB.
+	float32 GetLengthB() const;
+
+	/// Get the pulley ratio.
+	float32 GetRatio() const;
+
+	/// Dump joint to dmLog
+	void Dump();
+
+protected:
+
+	friend class b2Joint;
+	b2PulleyJoint(const b2PulleyJointDef* data);
+
+	void InitVelocityConstraints(const b2SolverData& data);
+	void SolveVelocityConstraints(const b2SolverData& data);
+	bool SolvePositionConstraints(const b2SolverData& data);
+
+	b2Vec2 m_groundAnchorA;
+	b2Vec2 m_groundAnchorB;
+	float32 m_lengthA;
+	float32 m_lengthB;
+
+	// Solver shared
+	b2Vec2 m_localAnchorA;
+	b2Vec2 m_localAnchorB;
+	float32 m_constant;
+	float32 m_ratio;
+	float32 m_impulse;
+
+	// Solver temp
+	juce::int32 m_indexA;
+	juce::int32 m_indexB;
+	b2Vec2 m_uA;
+	b2Vec2 m_uB;
+	b2Vec2 m_rA;
+	b2Vec2 m_rB;
+	b2Vec2 m_localCenterA;
+	b2Vec2 m_localCenterB;
+	float32 m_invMassA;
+	float32 m_invMassB;
+	float32 m_invIA;
+	float32 m_invIB;
+	float32 m_mass;
+};
+
+#endif

modules/juce_box2d/box2d/Dynamics/Joints/b2RevoluteJoint.cpp

@@ -0,0 +1,502 @@
+/*
+* Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#include "b2RevoluteJoint.h"
+#include "../b2Body.h"
+#include "../b2TimeStep.h"
+
+// Point-to-point constraint
+// C = p2 - p1
+// Cdot = v2 - v1
+//      = v2 + cross(w2, r2) - v1 - cross(w1, r1)
+// J = [-I -r1_skew I r2_skew ]
+// Identity used:
+// w k % (rx i + ry j) = w * (-ry i + rx j)
+
+// Motor constraint
+// Cdot = w2 - w1
+// J = [0 0 -1 0 0 1]
+// K = invI1 + invI2
+
+void b2RevoluteJointDef::Initialize(b2Body* bA, b2Body* bB, const b2Vec2& anchor)
+{
+	bodyA = bA;
+	bodyB = bB;
+	localAnchorA = bodyA->GetLocalPoint(anchor);
+	localAnchorB = bodyB->GetLocalPoint(anchor);
+	referenceAngle = bodyB->GetAngle() - bodyA->GetAngle();
+}
+
+b2RevoluteJoint::b2RevoluteJoint(const b2RevoluteJointDef* def)
+: b2Joint(def)
+{
+	m_localAnchorA = def->localAnchorA;
+	m_localAnchorB = def->localAnchorB;
+	m_referenceAngle = def->referenceAngle;
+
+	m_impulse.SetZero();
+	m_motorImpulse = 0.0f;
+
+	m_lowerAngle = def->lowerAngle;
+	m_upperAngle = def->upperAngle;
+	m_maxMotorTorque = def->maxMotorTorque;
+	m_motorSpeed = def->motorSpeed;
+	m_enableLimit = def->enableLimit;
+	m_enableMotor = def->enableMotor;
+	m_limitState = e_inactiveLimit;
+}
+
+void b2RevoluteJoint::InitVelocityConstraints(const b2SolverData& data)
+{
+	m_indexA = m_bodyA->m_islandIndex;
+	m_indexB = m_bodyB->m_islandIndex;
+	m_localCenterA = m_bodyA->m_sweep.localCenter;
+	m_localCenterB = m_bodyB->m_sweep.localCenter;
+	m_invMassA = m_bodyA->m_invMass;
+	m_invMassB = m_bodyB->m_invMass;
+	m_invIA = m_bodyA->m_invI;
+	m_invIB = m_bodyB->m_invI;
+
+	float32 aA = data.positions[m_indexA].a;
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float32 wA = data.velocities[m_indexA].w;
+
+	float32 aB = data.positions[m_indexB].a;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	b2Rot qA(aA), qB(aB);
+
+	m_rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
+	m_rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
+
+	// J = [-I -r1_skew I r2_skew]
+	//     [ 0       -1 0       1]
+	// r_skew = [-ry; rx]
+
+	// Matlab
+	// K = [ mA+r1y^2*iA+mB+r2y^2*iB,  -r1y*iA*r1x-r2y*iB*r2x,          -r1y*iA-r2y*iB]
+	//     [  -r1y*iA*r1x-r2y*iB*r2x, mA+r1x^2*iA+mB+r2x^2*iB,           r1x*iA+r2x*iB]
+	//     [          -r1y*iA-r2y*iB,           r1x*iA+r2x*iB,                   iA+iB]
+
+	float32 mA = m_invMassA, mB = m_invMassB;
+	float32 iA = m_invIA, iB = m_invIB;
+
+	bool fixedRotation = (iA + iB == 0.0f);
+
+	m_mass.ex.x = mA + mB + m_rA.y * m_rA.y * iA + m_rB.y * m_rB.y * iB;
+	m_mass.ey.x = -m_rA.y * m_rA.x * iA - m_rB.y * m_rB.x * iB;
+	m_mass.ez.x = -m_rA.y * iA - m_rB.y * iB;
+	m_mass.ex.y = m_mass.ey.x;
+	m_mass.ey.y = mA + mB + m_rA.x * m_rA.x * iA + m_rB.x * m_rB.x * iB;
+	m_mass.ez.y = m_rA.x * iA + m_rB.x * iB;
+	m_mass.ex.z = m_mass.ez.x;
+	m_mass.ey.z = m_mass.ez.y;
+	m_mass.ez.z = iA + iB;
+
+	m_motorMass = iA + iB;
+	if (m_motorMass > 0.0f)
+	{
+		m_motorMass = 1.0f / m_motorMass;
+	}
+
+	if (m_enableMotor == false || fixedRotation)
+	{
+		m_motorImpulse = 0.0f;
+	}
+
+	if (m_enableLimit && fixedRotation == false)
+	{
+		float32 jointAngle = aB - aA - m_referenceAngle;
+		if (b2Abs(m_upperAngle - m_lowerAngle) < 2.0f * b2_angularSlop)
+		{
+			m_limitState = e_equalLimits;
+		}
+		else if (jointAngle <= m_lowerAngle)
+		{
+			if (m_limitState != e_atLowerLimit)
+			{
+				m_impulse.z = 0.0f;
+			}
+			m_limitState = e_atLowerLimit;
+		}
+		else if (jointAngle >= m_upperAngle)
+		{
+			if (m_limitState != e_atUpperLimit)
+			{
+				m_impulse.z = 0.0f;
+			}
+			m_limitState = e_atUpperLimit;
+		}
+		else
+		{
+			m_limitState = e_inactiveLimit;
+			m_impulse.z = 0.0f;
+		}
+	}
+	else
+	{
+		m_limitState = e_inactiveLimit;
+	}
+
+	if (data.step.warmStarting)
+	{
+		// Scale impulses to support a variable time step.
+		m_impulse *= data.step.dtRatio;
+		m_motorImpulse *= data.step.dtRatio;
+
+		b2Vec2 P(m_impulse.x, m_impulse.y);
+
+		vA -= mA * P;
+		wA -= iA * (b2Cross(m_rA, P) + m_motorImpulse + m_impulse.z);
+
+		vB += mB * P;
+		wB += iB * (b2Cross(m_rB, P) + m_motorImpulse + m_impulse.z);
+	}
+	else
+	{
+		m_impulse.SetZero();
+		m_motorImpulse = 0.0f;
+	}
+
+	data.velocities[m_indexA].v = vA;
+	data.velocities[m_indexA].w = wA;
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+}
+
+void b2RevoluteJoint::SolveVelocityConstraints(const b2SolverData& data)
+{
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float32 wA = data.velocities[m_indexA].w;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	float32 mA = m_invMassA, mB = m_invMassB;
+	float32 iA = m_invIA, iB = m_invIB;
+
+	bool fixedRotation = (iA + iB == 0.0f);
+
+	// Solve motor constraint.
+	if (m_enableMotor && m_limitState != e_equalLimits && fixedRotation == false)
+	{
+		float32 Cdot = wB - wA - m_motorSpeed;
+		float32 impulse = -m_motorMass * Cdot;
+		float32 oldImpulse = m_motorImpulse;
+		float32 maxImpulse = data.step.dt * m_maxMotorTorque;
+		m_motorImpulse = b2Clamp(m_motorImpulse + impulse, -maxImpulse, maxImpulse);
+		impulse = m_motorImpulse - oldImpulse;
+
+		wA -= iA * impulse;
+		wB += iB * impulse;
+	}
+
+	// Solve limit constraint.
+	if (m_enableLimit && m_limitState != e_inactiveLimit && fixedRotation == false)
+	{
+		b2Vec2 Cdot1 = vB + b2Cross(wB, m_rB) - vA - b2Cross(wA, m_rA);
+		float32 Cdot2 = wB - wA;
+		b2Vec3 Cdot(Cdot1.x, Cdot1.y, Cdot2);
+
+		b2Vec3 impulse = -m_mass.Solve33(Cdot);
+
+		if (m_limitState == e_equalLimits)
+		{
+			m_impulse += impulse;
+		}
+		else if (m_limitState == e_atLowerLimit)
+		{
+			float32 newImpulse = m_impulse.z + impulse.z;
+			if (newImpulse < 0.0f)
+			{
+				b2Vec2 rhs = -Cdot1 + m_impulse.z * b2Vec2(m_mass.ez.x, m_mass.ez.y);
+				b2Vec2 reduced = m_mass.Solve22(rhs);
+				impulse.x = reduced.x;
+				impulse.y = reduced.y;
+				impulse.z = -m_impulse.z;
+				m_impulse.x += reduced.x;
+				m_impulse.y += reduced.y;
+				m_impulse.z = 0.0f;
+			}
+			else
+			{
+				m_impulse += impulse;
+			}
+		}
+		else if (m_limitState == e_atUpperLimit)
+		{
+			float32 newImpulse = m_impulse.z + impulse.z;
+			if (newImpulse > 0.0f)
+			{
+				b2Vec2 rhs = -Cdot1 + m_impulse.z * b2Vec2(m_mass.ez.x, m_mass.ez.y);
+				b2Vec2 reduced = m_mass.Solve22(rhs);
+				impulse.x = reduced.x;
+				impulse.y = reduced.y;
+				impulse.z = -m_impulse.z;
+				m_impulse.x += reduced.x;
+				m_impulse.y += reduced.y;
+				m_impulse.z = 0.0f;
+			}
+			else
+			{
+				m_impulse += impulse;
+			}
+		}
+
+		b2Vec2 P(impulse.x, impulse.y);
+
+		vA -= mA * P;
+		wA -= iA * (b2Cross(m_rA, P) + impulse.z);
+
+		vB += mB * P;
+		wB += iB * (b2Cross(m_rB, P) + impulse.z);
+	}
+	else
+	{
+		// Solve point-to-point constraint
+		b2Vec2 Cdot = vB + b2Cross(wB, m_rB) - vA - b2Cross(wA, m_rA);
+		b2Vec2 impulse = m_mass.Solve22(-Cdot);
+
+		m_impulse.x += impulse.x;
+		m_impulse.y += impulse.y;
+
+		vA -= mA * impulse;
+		wA -= iA * b2Cross(m_rA, impulse);
+
+		vB += mB * impulse;
+		wB += iB * b2Cross(m_rB, impulse);
+	}
+
+	data.velocities[m_indexA].v = vA;
+	data.velocities[m_indexA].w = wA;
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+}
+
+bool b2RevoluteJoint::SolvePositionConstraints(const b2SolverData& data)
+{
+	b2Vec2 cA = data.positions[m_indexA].c;
+	float32 aA = data.positions[m_indexA].a;
+	b2Vec2 cB = data.positions[m_indexB].c;
+	float32 aB = data.positions[m_indexB].a;
+
+	b2Rot qA(aA), qB(aB);
+
+	float32 angularError = 0.0f;
+	float32 positionError = 0.0f;
+
+	bool fixedRotation = (m_invIA + m_invIB == 0.0f);
+
+	// Solve angular limit constraint.
+	if (m_enableLimit && m_limitState != e_inactiveLimit && fixedRotation == false)
+	{
+		float32 angle = aB - aA - m_referenceAngle;
+		float32 limitImpulse = 0.0f;
+
+		if (m_limitState == e_equalLimits)
+		{
+			// Prevent large angular corrections
+			float32 C = b2Clamp(angle - m_lowerAngle, -b2_maxAngularCorrection, b2_maxAngularCorrection);
+			limitImpulse = -m_motorMass * C;
+			angularError = b2Abs(C);
+		}
+		else if (m_limitState == e_atLowerLimit)
+		{
+			float32 C = angle - m_lowerAngle;
+			angularError = -C;
+
+			// Prevent large angular corrections and allow some slop.
+			C = b2Clamp(C + b2_angularSlop, -b2_maxAngularCorrection, 0.0f);
+			limitImpulse = -m_motorMass * C;
+		}
+		else if (m_limitState == e_atUpperLimit)
+		{
+			float32 C = angle - m_upperAngle;
+			angularError = C;
+
+			// Prevent large angular corrections and allow some slop.
+			C = b2Clamp(C - b2_angularSlop, 0.0f, b2_maxAngularCorrection);
+			limitImpulse = -m_motorMass * C;
+		}
+
+		aA -= m_invIA * limitImpulse;
+		aB += m_invIB * limitImpulse;
+	}
+
+	// Solve point-to-point constraint.
+	{
+		qA.Set(aA);
+		qB.Set(aB);
+		b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
+		b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
+
+		b2Vec2 C = cB + rB - cA - rA;
+		positionError = C.Length();
+
+		float32 mA = m_invMassA, mB = m_invMassB;
+		float32 iA = m_invIA, iB = m_invIB;
+
+		b2Mat22 K;
+		K.ex.x = mA + mB + iA * rA.y * rA.y + iB * rB.y * rB.y;
+		K.ex.y = -iA * rA.x * rA.y - iB * rB.x * rB.y;
+		K.ey.x = K.ex.y;
+		K.ey.y = mA + mB + iA * rA.x * rA.x + iB * rB.x * rB.x;
+
+		b2Vec2 impulse = -K.Solve(C);
+
+		cA -= mA * impulse;
+		aA -= iA * b2Cross(rA, impulse);
+
+		cB += mB * impulse;
+		aB += iB * b2Cross(rB, impulse);
+	}
+
+	data.positions[m_indexA].c = cA;
+	data.positions[m_indexA].a = aA;
+	data.positions[m_indexB].c = cB;
+	data.positions[m_indexB].a = aB;
+
+	return positionError <= b2_linearSlop && angularError <= b2_angularSlop;
+}
+
+b2Vec2 b2RevoluteJoint::GetAnchorA() const
+{
+	return m_bodyA->GetWorldPoint(m_localAnchorA);
+}
+
+b2Vec2 b2RevoluteJoint::GetAnchorB() const
+{
+	return m_bodyB->GetWorldPoint(m_localAnchorB);
+}
+
+b2Vec2 b2RevoluteJoint::GetReactionForce(float32 inv_dt) const
+{
+	b2Vec2 P(m_impulse.x, m_impulse.y);
+	return inv_dt * P;
+}
+
+float32 b2RevoluteJoint::GetReactionTorque(float32 inv_dt) const
+{
+	return inv_dt * m_impulse.z;
+}
+
+float32 b2RevoluteJoint::GetJointAngle() const
+{
+	b2Body* bA = m_bodyA;
+	b2Body* bB = m_bodyB;
+	return bB->m_sweep.a - bA->m_sweep.a - m_referenceAngle;
+}
+
+float32 b2RevoluteJoint::GetJointSpeed() const
+{
+	b2Body* bA = m_bodyA;
+	b2Body* bB = m_bodyB;
+	return bB->m_angularVelocity - bA->m_angularVelocity;
+}
+
+bool b2RevoluteJoint::IsMotorEnabled() const
+{
+	return m_enableMotor;
+}
+
+void b2RevoluteJoint::EnableMotor(bool flag)
+{
+	m_bodyA->SetAwake(true);
+	m_bodyB->SetAwake(true);
+	m_enableMotor = flag;
+}
+
+float32 b2RevoluteJoint::GetMotorTorque(float32 inv_dt) const
+{
+	return inv_dt * m_motorImpulse;
+}
+
+void b2RevoluteJoint::SetMotorSpeed(float32 speed)
+{
+	m_bodyA->SetAwake(true);
+	m_bodyB->SetAwake(true);
+	m_motorSpeed = speed;
+}
+
+void b2RevoluteJoint::SetMaxMotorTorque(float32 torque)
+{
+	m_bodyA->SetAwake(true);
+	m_bodyB->SetAwake(true);
+	m_maxMotorTorque = torque;
+}
+
+bool b2RevoluteJoint::IsLimitEnabled() const
+{
+	return m_enableLimit;
+}
+
+void b2RevoluteJoint::EnableLimit(bool flag)
+{
+	if (flag != m_enableLimit)
+	{
+		m_bodyA->SetAwake(true);
+		m_bodyB->SetAwake(true);
+		m_enableLimit = flag;
+		m_impulse.z = 0.0f;
+	}
+}
+
+float32 b2RevoluteJoint::GetLowerLimit() const
+{
+	return m_lowerAngle;
+}
+
+float32 b2RevoluteJoint::GetUpperLimit() const
+{
+	return m_upperAngle;
+}
+
+void b2RevoluteJoint::SetLimits(float32 lower, float32 upper)
+{
+	b2Assert(lower <= upper);
+
+	if (lower != m_lowerAngle || upper != m_upperAngle)
+	{
+		m_bodyA->SetAwake(true);
+		m_bodyB->SetAwake(true);
+		m_impulse.z = 0.0f;
+		m_lowerAngle = lower;
+		m_upperAngle = upper;
+	}
+}
+
+void b2RevoluteJoint::Dump()
+{
+	int32 indexA = m_bodyA->m_islandIndex;
+	int32 indexB = m_bodyB->m_islandIndex;
+
+	b2Log("  b2RevoluteJointDef jd;\n");
+	b2Log("  jd.bodyA = bodies[%d];\n", indexA);
+	b2Log("  jd.bodyB = bodies[%d];\n", indexB);
+	b2Log("  jd.collideConnected = bool(%d);\n", m_collideConnected);
+	b2Log("  jd.localAnchorA.Set(%.15lef, %.15lef);\n", m_localAnchorA.x, m_localAnchorA.y);
+	b2Log("  jd.localAnchorB.Set(%.15lef, %.15lef);\n", m_localAnchorB.x, m_localAnchorB.y);
+	b2Log("  jd.referenceAngle = %.15lef;\n", m_referenceAngle);
+	b2Log("  jd.enableLimit = bool(%d);\n", m_enableLimit);
+	b2Log("  jd.lowerAngle = %.15lef;\n", m_lowerAngle);
+	b2Log("  jd.upperAngle = %.15lef;\n", m_upperAngle);
+	b2Log("  jd.enableMotor = bool(%d);\n", m_enableMotor);
+	b2Log("  jd.motorSpeed = %.15lef;\n", m_motorSpeed);
+	b2Log("  jd.maxMotorTorque = %.15lef;\n", m_maxMotorTorque);
+	b2Log("  joints[%d] = m_world->CreateJoint(&jd);\n", m_index);
+}

modules/juce_box2d/box2d/Dynamics/Joints/b2RevoluteJoint.h

@@ -0,0 +1,204 @@
+/*
+* Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#ifndef B2_REVOLUTE_JOINT_H
+#define B2_REVOLUTE_JOINT_H
+
+#include "b2Joint.h"
+
+/// Revolute joint definition. This requires defining an
+/// anchor point where the bodies are joined. The definition
+/// uses local anchor points so that the initial configuration
+/// can violate the constraint slightly. You also need to
+/// specify the initial relative angle for joint limits. This
+/// helps when saving and loading a game.
+/// The local anchor points are measured from the body's origin
+/// rather than the center of mass because:
+/// 1. you might not know where the center of mass will be.
+/// 2. if you add/remove shapes from a body and recompute the mass,
+///    the joints will be broken.
+struct b2RevoluteJointDef : public b2JointDef
+{
+	b2RevoluteJointDef()
+	{
+		type = e_revoluteJoint;
+		localAnchorA.Set(0.0f, 0.0f);
+		localAnchorB.Set(0.0f, 0.0f);
+		referenceAngle = 0.0f;
+		lowerAngle = 0.0f;
+		upperAngle = 0.0f;
+		maxMotorTorque = 0.0f;
+		motorSpeed = 0.0f;
+		enableLimit = false;
+		enableMotor = false;
+	}
+
+	/// Initialize the bodies, anchors, and reference angle using a world
+	/// anchor point.
+	void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor);
+
+	/// The local anchor point relative to bodyA's origin.
+	b2Vec2 localAnchorA;
+
+	/// The local anchor point relative to bodyB's origin.
+	b2Vec2 localAnchorB;
+
+	/// The bodyB angle minus bodyA angle in the reference state (radians).
+	float32 referenceAngle;
+
+	/// A flag to enable joint limits.
+	bool enableLimit;
+
+	/// The lower angle for the joint limit (radians).
+	float32 lowerAngle;
+
+	/// The upper angle for the joint limit (radians).
+	float32 upperAngle;
+
+	/// A flag to enable the joint motor.
+	bool enableMotor;
+
+	/// The desired motor speed. Usually in radians per second.
+	float32 motorSpeed;
+
+	/// The maximum motor torque used to achieve the desired motor speed.
+	/// Usually in N-m.
+	float32 maxMotorTorque;
+};
+
+/// A revolute joint constrains two bodies to share a common point while they
+/// are free to rotate about the point. The relative rotation about the shared
+/// point is the joint angle. You can limit the relative rotation with
+/// a joint limit that specifies a lower and upper angle. You can use a motor
+/// to drive the relative rotation about the shared point. A maximum motor torque
+/// is provided so that infinite forces are not generated.
+class b2RevoluteJoint : public b2Joint
+{
+public:
+	b2Vec2 GetAnchorA() const;
+	b2Vec2 GetAnchorB() const;
+
+	/// The local anchor point relative to bodyA's origin.
+	const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }
+
+	/// The local anchor point relative to bodyB's origin.
+	const b2Vec2& GetLocalAnchorB() const  { return m_localAnchorB; }
+
+	/// Get the reference angle.
+	float32 GetReferenceAngle() const { return m_referenceAngle; }
+
+	/// Get the current joint angle in radians.
+	float32 GetJointAngle() const;
+
+	/// Get the current joint angle speed in radians per second.
+	float32 GetJointSpeed() const;
+
+	/// Is the joint limit enabled?
+	bool IsLimitEnabled() const;
+
+	/// Enable/disable the joint limit.
+	void EnableLimit(bool flag);
+
+	/// Get the lower joint limit in radians.
+	float32 GetLowerLimit() const;
+
+	/// Get the upper joint limit in radians.
+	float32 GetUpperLimit() const;
+
+	/// Set the joint limits in radians.
+	void SetLimits(float32 lower, float32 upper);
+
+	/// Is the joint motor enabled?
+	bool IsMotorEnabled() const;
+
+	/// Enable/disable the joint motor.
+	void EnableMotor(bool flag);
+
+	/// Set the motor speed in radians per second.
+	void SetMotorSpeed(float32 speed);
+
+	/// Get the motor speed in radians per second.
+	float32 GetMotorSpeed() const;
+
+	/// Set the maximum motor torque, usually in N-m.
+	void SetMaxMotorTorque(float32 torque);
+	float32 GetMaxMotorTorque() const { return m_maxMotorTorque; }
+
+	/// Get the reaction force given the inverse time step.
+	/// Unit is N.
+	b2Vec2 GetReactionForce(float32 inv_dt) const;
+
+	/// Get the reaction torque due to the joint limit given the inverse time step.
+	/// Unit is N*m.
+	float32 GetReactionTorque(float32 inv_dt) const;
+
+	/// Get the current motor torque given the inverse time step.
+	/// Unit is N*m.
+	float32 GetMotorTorque(float32 inv_dt) const;
+
+	/// Dump to b2Log.
+	void Dump();
+
+protected:
+
+	friend class b2Joint;
+	friend class b2GearJoint;
+
+	b2RevoluteJoint(const b2RevoluteJointDef* def);
+
+	void InitVelocityConstraints(const b2SolverData& data);
+	void SolveVelocityConstraints(const b2SolverData& data);
+	bool SolvePositionConstraints(const b2SolverData& data);
+
+	// Solver shared
+	b2Vec2 m_localAnchorA;
+	b2Vec2 m_localAnchorB;
+	b2Vec3 m_impulse;
+	float32 m_motorImpulse;
+
+	bool m_enableMotor;
+	float32 m_maxMotorTorque;
+	float32 m_motorSpeed;
+
+	bool m_enableLimit;
+	float32 m_referenceAngle;
+	float32 m_lowerAngle;
+	float32 m_upperAngle;
+
+	// Solver temp
+	juce::int32 m_indexA;
+	juce::int32 m_indexB;
+	b2Vec2 m_rA;
+	b2Vec2 m_rB;
+	b2Vec2 m_localCenterA;
+	b2Vec2 m_localCenterB;
+	float32 m_invMassA;
+	float32 m_invMassB;
+	float32 m_invIA;
+	float32 m_invIB;
+	b2Mat33 m_mass;			// effective mass for point-to-point constraint.
+	float32 m_motorMass;	// effective mass for motor/limit angular constraint.
+	b2LimitState m_limitState;
+};
+
+inline float32 b2RevoluteJoint::GetMotorSpeed() const
+{
+	return m_motorSpeed;
+}
+
+#endif

modules/juce_box2d/box2d/Dynamics/Joints/b2RopeJoint.cpp

@@ -0,0 +1,241 @@
+/*
+* Copyright (c) 2007-2011 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#include "b2RopeJoint.h"
+#include "../b2Body.h"
+#include "../b2TimeStep.h"
+
+
+// Limit:
+// C = norm(pB - pA) - L
+// u = (pB - pA) / norm(pB - pA)
+// Cdot = dot(u, vB + cross(wB, rB) - vA - cross(wA, rA))
+// J = [-u -cross(rA, u) u cross(rB, u)]
+// K = J * invM * JT
+//   = invMassA + invIA * cross(rA, u)^2 + invMassB + invIB * cross(rB, u)^2
+
+b2RopeJoint::b2RopeJoint(const b2RopeJointDef* def)
+: b2Joint(def)
+{
+	m_localAnchorA = def->localAnchorA;
+	m_localAnchorB = def->localAnchorB;
+
+	m_maxLength = def->maxLength;
+
+	m_mass = 0.0f;
+	m_impulse = 0.0f;
+	m_state = e_inactiveLimit;
+	m_length = 0.0f;
+}
+
+void b2RopeJoint::InitVelocityConstraints(const b2SolverData& data)
+{
+	m_indexA = m_bodyA->m_islandIndex;
+	m_indexB = m_bodyB->m_islandIndex;
+	m_localCenterA = m_bodyA->m_sweep.localCenter;
+	m_localCenterB = m_bodyB->m_sweep.localCenter;
+	m_invMassA = m_bodyA->m_invMass;
+	m_invMassB = m_bodyB->m_invMass;
+	m_invIA = m_bodyA->m_invI;
+	m_invIB = m_bodyB->m_invI;
+
+	b2Vec2 cA = data.positions[m_indexA].c;
+	float32 aA = data.positions[m_indexA].a;
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float32 wA = data.velocities[m_indexA].w;
+
+	b2Vec2 cB = data.positions[m_indexB].c;
+	float32 aB = data.positions[m_indexB].a;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	b2Rot qA(aA), qB(aB);
+
+	m_rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
+	m_rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
+	m_u = cB + m_rB - cA - m_rA;
+
+	m_length = m_u.Length();
+
+	float32 C = m_length - m_maxLength;
+	if (C > 0.0f)
+	{
+		m_state = e_atUpperLimit;
+	}
+	else
+	{
+		m_state = e_inactiveLimit;
+	}
+
+	if (m_length > b2_linearSlop)
+	{
+		m_u *= 1.0f / m_length;
+	}
+	else
+	{
+		m_u.SetZero();
+		m_mass = 0.0f;
+		m_impulse = 0.0f;
+		return;
+	}
+
+	// Compute effective mass.
+	float32 crA = b2Cross(m_rA, m_u);
+	float32 crB = b2Cross(m_rB, m_u);
+	float32 invMass = m_invMassA + m_invIA * crA * crA + m_invMassB + m_invIB * crB * crB;
+
+	m_mass = invMass != 0.0f ? 1.0f / invMass : 0.0f;
+
+	if (data.step.warmStarting)
+	{
+		// Scale the impulse to support a variable time step.
+		m_impulse *= data.step.dtRatio;
+
+		b2Vec2 P = m_impulse * m_u;
+		vA -= m_invMassA * P;
+		wA -= m_invIA * b2Cross(m_rA, P);
+		vB += m_invMassB * P;
+		wB += m_invIB * b2Cross(m_rB, P);
+	}
+	else
+	{
+		m_impulse = 0.0f;
+	}
+
+	data.velocities[m_indexA].v = vA;
+	data.velocities[m_indexA].w = wA;
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+}
+
+void b2RopeJoint::SolveVelocityConstraints(const b2SolverData& data)
+{
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float32 wA = data.velocities[m_indexA].w;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	// Cdot = dot(u, v + cross(w, r))
+	b2Vec2 vpA = vA + b2Cross(wA, m_rA);
+	b2Vec2 vpB = vB + b2Cross(wB, m_rB);
+	float32 C = m_length - m_maxLength;
+	float32 Cdot = b2Dot(m_u, vpB - vpA);
+
+	// Predictive constraint.
+	if (C < 0.0f)
+	{
+		Cdot += data.step.inv_dt * C;
+	}
+
+	float32 impulse = -m_mass * Cdot;
+	float32 oldImpulse = m_impulse;
+	m_impulse = b2Min(0.0f, m_impulse + impulse);
+	impulse = m_impulse - oldImpulse;
+
+	b2Vec2 P = impulse * m_u;
+	vA -= m_invMassA * P;
+	wA -= m_invIA * b2Cross(m_rA, P);
+	vB += m_invMassB * P;
+	wB += m_invIB * b2Cross(m_rB, P);
+
+	data.velocities[m_indexA].v = vA;
+	data.velocities[m_indexA].w = wA;
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+}
+
+bool b2RopeJoint::SolvePositionConstraints(const b2SolverData& data)
+{
+	b2Vec2 cA = data.positions[m_indexA].c;
+	float32 aA = data.positions[m_indexA].a;
+	b2Vec2 cB = data.positions[m_indexB].c;
+	float32 aB = data.positions[m_indexB].a;
+
+	b2Rot qA(aA), qB(aB);
+
+	b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
+	b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
+	b2Vec2 u = cB + rB - cA - rA;
+
+	float32 length = u.Normalize();
+	float32 C = length - m_maxLength;
+
+	C = b2Clamp(C, 0.0f, b2_maxLinearCorrection);
+
+	float32 impulse = -m_mass * C;
+	b2Vec2 P = impulse * u;
+
+	cA -= m_invMassA * P;
+	aA -= m_invIA * b2Cross(rA, P);
+	cB += m_invMassB * P;
+	aB += m_invIB * b2Cross(rB, P);
+
+	data.positions[m_indexA].c = cA;
+	data.positions[m_indexA].a = aA;
+	data.positions[m_indexB].c = cB;
+	data.positions[m_indexB].a = aB;
+
+	return length - m_maxLength < b2_linearSlop;
+}
+
+b2Vec2 b2RopeJoint::GetAnchorA() const
+{
+	return m_bodyA->GetWorldPoint(m_localAnchorA);
+}
+
+b2Vec2 b2RopeJoint::GetAnchorB() const
+{
+	return m_bodyB->GetWorldPoint(m_localAnchorB);
+}
+
+b2Vec2 b2RopeJoint::GetReactionForce(float32 inv_dt) const
+{
+	b2Vec2 F = (inv_dt * m_impulse) * m_u;
+	return F;
+}
+
+float32 b2RopeJoint::GetReactionTorque(float32 inv_dt) const
+{
+	B2_NOT_USED(inv_dt);
+	return 0.0f;
+}
+
+float32 b2RopeJoint::GetMaxLength() const
+{
+	return m_maxLength;
+}
+
+b2LimitState b2RopeJoint::GetLimitState() const
+{
+	return m_state;
+}
+
+void b2RopeJoint::Dump()
+{
+	int32 indexA = m_bodyA->m_islandIndex;
+	int32 indexB = m_bodyB->m_islandIndex;
+
+	b2Log("  b2RopeJointDef jd;\n");
+	b2Log("  jd.bodyA = bodies[%d];\n", indexA);
+	b2Log("  jd.bodyB = bodies[%d];\n", indexB);
+	b2Log("  jd.collideConnected = bool(%d);\n", m_collideConnected);
+	b2Log("  jd.localAnchorA.Set(%.15lef, %.15lef);\n", m_localAnchorA.x, m_localAnchorA.y);
+	b2Log("  jd.localAnchorB.Set(%.15lef, %.15lef);\n", m_localAnchorB.x, m_localAnchorB.y);
+	b2Log("  jd.maxLength = %.15lef;\n", m_maxLength);
+	b2Log("  joints[%d] = m_world->CreateJoint(&jd);\n", m_index);
+}

modules/juce_box2d/box2d/Dynamics/Joints/b2RopeJoint.h

@@ -0,0 +1,114 @@
+/*
+* Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#ifndef B2_ROPE_JOINT_H
+#define B2_ROPE_JOINT_H
+
+#include "b2Joint.h"
+
+/// Rope joint definition. This requires two body anchor points and
+/// a maximum lengths.
+/// Note: by default the connected objects will not collide.
+/// see collideConnected in b2JointDef.
+struct b2RopeJointDef : public b2JointDef
+{
+	b2RopeJointDef()
+	{
+		type = e_ropeJoint;
+		localAnchorA.Set(-1.0f, 0.0f);
+		localAnchorB.Set(1.0f, 0.0f);
+		maxLength = 0.0f;
+	}
+
+	/// The local anchor point relative to bodyA's origin.
+	b2Vec2 localAnchorA;
+
+	/// The local anchor point relative to bodyB's origin.
+	b2Vec2 localAnchorB;
+
+	/// The maximum length of the rope.
+	/// Warning: this must be larger than b2_linearSlop or
+	/// the joint will have no effect.
+	float32 maxLength;
+};
+
+/// A rope joint enforces a maximum distance between two points
+/// on two bodies. It has no other effect.
+/// Warning: if you attempt to change the maximum length during
+/// the simulation you will get some non-physical behavior.
+/// A model that would allow you to dynamically modify the length
+/// would have some sponginess, so I chose not to implement it
+/// that way. See b2DistanceJoint if you want to dynamically
+/// control length.
+class b2RopeJoint : public b2Joint
+{
+public:
+	b2Vec2 GetAnchorA() const;
+	b2Vec2 GetAnchorB() const;
+
+	b2Vec2 GetReactionForce(float32 inv_dt) const;
+	float32 GetReactionTorque(float32 inv_dt) const;
+
+	/// The local anchor point relative to bodyA's origin.
+	const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }
+
+	/// The local anchor point relative to bodyB's origin.
+	const b2Vec2& GetLocalAnchorB() const  { return m_localAnchorB; }
+
+	/// Set/Get the maximum length of the rope.
+	void SetMaxLength(float32 length) { m_maxLength = length; }
+	float32 GetMaxLength() const;
+
+	b2LimitState GetLimitState() const;
+
+	/// Dump joint to dmLog
+	void Dump();
+
+protected:
+
+	friend class b2Joint;
+	b2RopeJoint(const b2RopeJointDef* data);
+
+	void InitVelocityConstraints(const b2SolverData& data);
+	void SolveVelocityConstraints(const b2SolverData& data);
+	bool SolvePositionConstraints(const b2SolverData& data);
+
+	// Solver shared
+	b2Vec2 m_localAnchorA;
+	b2Vec2 m_localAnchorB;
+	float32 m_maxLength;
+	float32 m_length;
+	float32 m_impulse;
+
+	// Solver temp
+	juce::int32 m_indexA;
+	juce::int32 m_indexB;
+	b2Vec2 m_u;
+	b2Vec2 m_rA;
+	b2Vec2 m_rB;
+	b2Vec2 m_localCenterA;
+	b2Vec2 m_localCenterB;
+	float32 m_invMassA;
+	float32 m_invMassB;
+	float32 m_invIA;
+	float32 m_invIB;
+	float32 m_mass;
+	b2LimitState m_state;
+};
+
+#endif

modules/juce_box2d/box2d/Dynamics/Joints/b2WeldJoint.cpp

@@ -0,0 +1,328 @@
+/*
+* Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#include "b2WeldJoint.h"
+#include "../b2Body.h"
+#include "../b2TimeStep.h"
+
+// Point-to-point constraint
+// C = p2 - p1
+// Cdot = v2 - v1
+//      = v2 + cross(w2, r2) - v1 - cross(w1, r1)
+// J = [-I -r1_skew I r2_skew ]
+// Identity used:
+// w k % (rx i + ry j) = w * (-ry i + rx j)
+
+// Angle constraint
+// C = angle2 - angle1 - referenceAngle
+// Cdot = w2 - w1
+// J = [0 0 -1 0 0 1]
+// K = invI1 + invI2
+
+void b2WeldJointDef::Initialize(b2Body* bA, b2Body* bB, const b2Vec2& anchor)
+{
+	bodyA = bA;
+	bodyB = bB;
+	localAnchorA = bodyA->GetLocalPoint(anchor);
+	localAnchorB = bodyB->GetLocalPoint(anchor);
+	referenceAngle = bodyB->GetAngle() - bodyA->GetAngle();
+}
+
+b2WeldJoint::b2WeldJoint(const b2WeldJointDef* def)
+: b2Joint(def)
+{
+	m_localAnchorA = def->localAnchorA;
+	m_localAnchorB = def->localAnchorB;
+	m_referenceAngle = def->referenceAngle;
+	m_frequencyHz = def->frequencyHz;
+	m_dampingRatio = def->dampingRatio;
+
+	m_impulse.SetZero();
+}
+
+void b2WeldJoint::InitVelocityConstraints(const b2SolverData& data)
+{
+	m_indexA = m_bodyA->m_islandIndex;
+	m_indexB = m_bodyB->m_islandIndex;
+	m_localCenterA = m_bodyA->m_sweep.localCenter;
+	m_localCenterB = m_bodyB->m_sweep.localCenter;
+	m_invMassA = m_bodyA->m_invMass;
+	m_invMassB = m_bodyB->m_invMass;
+	m_invIA = m_bodyA->m_invI;
+	m_invIB = m_bodyB->m_invI;
+
+	float32 aA = data.positions[m_indexA].a;
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float32 wA = data.velocities[m_indexA].w;
+
+	float32 aB = data.positions[m_indexB].a;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	b2Rot qA(aA), qB(aB);
+
+	m_rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
+	m_rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
+
+	// J = [-I -r1_skew I r2_skew]
+	//     [ 0       -1 0       1]
+	// r_skew = [-ry; rx]
+
+	// Matlab
+	// K = [ mA+r1y^2*iA+mB+r2y^2*iB,  -r1y*iA*r1x-r2y*iB*r2x,          -r1y*iA-r2y*iB]
+	//     [  -r1y*iA*r1x-r2y*iB*r2x, mA+r1x^2*iA+mB+r2x^2*iB,           r1x*iA+r2x*iB]
+	//     [          -r1y*iA-r2y*iB,           r1x*iA+r2x*iB,                   iA+iB]
+
+	float32 mA = m_invMassA, mB = m_invMassB;
+	float32 iA = m_invIA, iB = m_invIB;
+
+	b2Mat33 K;
+	K.ex.x = mA + mB + m_rA.y * m_rA.y * iA + m_rB.y * m_rB.y * iB;
+	K.ey.x = -m_rA.y * m_rA.x * iA - m_rB.y * m_rB.x * iB;
+	K.ez.x = -m_rA.y * iA - m_rB.y * iB;
+	K.ex.y = K.ey.x;
+	K.ey.y = mA + mB + m_rA.x * m_rA.x * iA + m_rB.x * m_rB.x * iB;
+	K.ez.y = m_rA.x * iA + m_rB.x * iB;
+	K.ex.z = K.ez.x;
+	K.ey.z = K.ez.y;
+	K.ez.z = iA + iB;
+
+	if (m_frequencyHz > 0.0f)
+	{
+		K.GetInverse22(&m_mass);
+
+		float32 invM = iA + iB;
+		float32 m = invM > 0.0f ? 1.0f / invM : 0.0f;
+
+		float32 C = aB - aA - m_referenceAngle;
+
+		// Frequency
+		float32 omega = 2.0f * b2_pi * m_frequencyHz;
+
+		// Damping coefficient
+		float32 d = 2.0f * m * m_dampingRatio * omega;
+
+		// Spring stiffness
+		float32 k = m * omega * omega;
+
+		// magic formulas
+		float32 h = data.step.dt;
+		m_gamma = h * (d + h * k);
+		m_gamma = m_gamma != 0.0f ? 1.0f / m_gamma : 0.0f;
+		m_bias = C * h * k * m_gamma;
+
+		invM += m_gamma;
+		m_mass.ez.z = invM != 0.0f ? 1.0f / invM : 0.0f;
+	}
+	else
+	{
+		K.GetSymInverse33(&m_mass);
+		m_gamma = 0.0f;
+		m_bias = 0.0f;
+	}
+
+	if (data.step.warmStarting)
+	{
+		// Scale impulses to support a variable time step.
+		m_impulse *= data.step.dtRatio;
+
+		b2Vec2 P(m_impulse.x, m_impulse.y);
+
+		vA -= mA * P;
+		wA -= iA * (b2Cross(m_rA, P) + m_impulse.z);
+
+		vB += mB * P;
+		wB += iB * (b2Cross(m_rB, P) + m_impulse.z);
+	}
+	else
+	{
+		m_impulse.SetZero();
+	}
+
+	data.velocities[m_indexA].v = vA;
+	data.velocities[m_indexA].w = wA;
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+}
+
+void b2WeldJoint::SolveVelocityConstraints(const b2SolverData& data)
+{
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float32 wA = data.velocities[m_indexA].w;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	float32 mA = m_invMassA, mB = m_invMassB;
+	float32 iA = m_invIA, iB = m_invIB;
+
+	if (m_frequencyHz > 0.0f)
+	{
+		float32 Cdot2 = wB - wA;
+
+		float32 impulse2 = -m_mass.ez.z * (Cdot2 + m_bias + m_gamma * m_impulse.z);
+		m_impulse.z += impulse2;
+
+		wA -= iA * impulse2;
+		wB += iB * impulse2;
+
+		b2Vec2 Cdot1 = vB + b2Cross(wB, m_rB) - vA - b2Cross(wA, m_rA);
+
+		b2Vec2 impulse1 = -b2Mul22(m_mass, Cdot1);
+		m_impulse.x += impulse1.x;
+		m_impulse.y += impulse1.y;
+
+		b2Vec2 P = impulse1;
+
+		vA -= mA * P;
+		wA -= iA * b2Cross(m_rA, P);
+
+		vB += mB * P;
+		wB += iB * b2Cross(m_rB, P);
+	}
+	else
+	{
+		b2Vec2 Cdot1 = vB + b2Cross(wB, m_rB) - vA - b2Cross(wA, m_rA);
+		float32 Cdot2 = wB - wA;
+		b2Vec3 Cdot(Cdot1.x, Cdot1.y, Cdot2);
+
+		b2Vec3 impulse = -b2Mul(m_mass, Cdot);
+		m_impulse += impulse;
+
+		b2Vec2 P(impulse.x, impulse.y);
+
+		vA -= mA * P;
+		wA -= iA * (b2Cross(m_rA, P) + impulse.z);
+
+		vB += mB * P;
+		wB += iB * (b2Cross(m_rB, P) + impulse.z);
+	}
+
+	data.velocities[m_indexA].v = vA;
+	data.velocities[m_indexA].w = wA;
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+}
+
+bool b2WeldJoint::SolvePositionConstraints(const b2SolverData& data)
+{
+	b2Vec2 cA = data.positions[m_indexA].c;
+	float32 aA = data.positions[m_indexA].a;
+	b2Vec2 cB = data.positions[m_indexB].c;
+	float32 aB = data.positions[m_indexB].a;
+
+	b2Rot qA(aA), qB(aB);
+
+	float32 mA = m_invMassA, mB = m_invMassB;
+	float32 iA = m_invIA, iB = m_invIB;
+
+	b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
+	b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
+
+	float32 positionError, angularError;
+
+	b2Mat33 K;
+	K.ex.x = mA + mB + rA.y * rA.y * iA + rB.y * rB.y * iB;
+	K.ey.x = -rA.y * rA.x * iA - rB.y * rB.x * iB;
+	K.ez.x = -rA.y * iA - rB.y * iB;
+	K.ex.y = K.ey.x;
+	K.ey.y = mA + mB + rA.x * rA.x * iA + rB.x * rB.x * iB;
+	K.ez.y = rA.x * iA + rB.x * iB;
+	K.ex.z = K.ez.x;
+	K.ey.z = K.ez.y;
+	K.ez.z = iA + iB;
+
+	if (m_frequencyHz > 0.0f)
+	{
+		b2Vec2 C1 =  cB + rB - cA - rA;
+
+		positionError = C1.Length();
+		angularError = 0.0f;
+
+		b2Vec2 P = -K.Solve22(C1);
+
+		cA -= mA * P;
+		aA -= iA * b2Cross(rA, P);
+
+		cB += mB * P;
+		aB += iB * b2Cross(rB, P);
+	}
+	else
+	{
+		b2Vec2 C1 =  cB + rB - cA - rA;
+		float32 C2 = aB - aA - m_referenceAngle;
+
+		positionError = C1.Length();
+		angularError = b2Abs(C2);
+
+		b2Vec3 C(C1.x, C1.y, C2);
+
+		b2Vec3 impulse = -K.Solve33(C);
+		b2Vec2 P(impulse.x, impulse.y);
+
+		cA -= mA * P;
+		aA -= iA * (b2Cross(rA, P) + impulse.z);
+
+		cB += mB * P;
+		aB += iB * (b2Cross(rB, P) + impulse.z);
+	}
+
+	data.positions[m_indexA].c = cA;
+	data.positions[m_indexA].a = aA;
+	data.positions[m_indexB].c = cB;
+	data.positions[m_indexB].a = aB;
+
+	return positionError <= b2_linearSlop && angularError <= b2_angularSlop;
+}
+
+b2Vec2 b2WeldJoint::GetAnchorA() const
+{
+	return m_bodyA->GetWorldPoint(m_localAnchorA);
+}
+
+b2Vec2 b2WeldJoint::GetAnchorB() const
+{
+	return m_bodyB->GetWorldPoint(m_localAnchorB);
+}
+
+b2Vec2 b2WeldJoint::GetReactionForce(float32 inv_dt) const
+{
+	b2Vec2 P(m_impulse.x, m_impulse.y);
+	return inv_dt * P;
+}
+
+float32 b2WeldJoint::GetReactionTorque(float32 inv_dt) const
+{
+	return inv_dt * m_impulse.z;
+}
+
+void b2WeldJoint::Dump()
+{
+	int32 indexA = m_bodyA->m_islandIndex;
+	int32 indexB = m_bodyB->m_islandIndex;
+
+	b2Log("  b2WeldJointDef jd;\n");
+	b2Log("  jd.bodyA = bodies[%d];\n", indexA);
+	b2Log("  jd.bodyB = bodies[%d];\n", indexB);
+	b2Log("  jd.collideConnected = bool(%d);\n", m_collideConnected);
+	b2Log("  jd.localAnchorA.Set(%.15lef, %.15lef);\n", m_localAnchorA.x, m_localAnchorA.y);
+	b2Log("  jd.localAnchorB.Set(%.15lef, %.15lef);\n", m_localAnchorB.x, m_localAnchorB.y);
+	b2Log("  jd.referenceAngle = %.15lef;\n", m_referenceAngle);
+	b2Log("  jd.frequencyHz = %.15lef;\n", m_frequencyHz);
+	b2Log("  jd.dampingRatio = %.15lef;\n", m_dampingRatio);
+	b2Log("  joints[%d] = m_world->CreateJoint(&jd);\n", m_index);
+}

modules/juce_box2d/box2d/Dynamics/Joints/b2WeldJoint.h

@@ -0,0 +1,126 @@
+/*
+* Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#ifndef B2_WELD_JOINT_H
+#define B2_WELD_JOINT_H
+
+#include "b2Joint.h"
+
+/// Weld joint definition. You need to specify local anchor points
+/// where they are attached and the relative body angle. The position
+/// of the anchor points is important for computing the reaction torque.
+struct b2WeldJointDef : public b2JointDef
+{
+	b2WeldJointDef()
+	{
+		type = e_weldJoint;
+		localAnchorA.Set(0.0f, 0.0f);
+		localAnchorB.Set(0.0f, 0.0f);
+		referenceAngle = 0.0f;
+		frequencyHz = 0.0f;
+		dampingRatio = 0.0f;
+	}
+
+	/// Initialize the bodies, anchors, and reference angle using a world
+	/// anchor point.
+	void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor);
+
+	/// The local anchor point relative to bodyA's origin.
+	b2Vec2 localAnchorA;
+
+	/// The local anchor point relative to bodyB's origin.
+	b2Vec2 localAnchorB;
+
+	/// The bodyB angle minus bodyA angle in the reference state (radians).
+	float32 referenceAngle;
+
+	/// The mass-spring-damper frequency in Hertz. Rotation only.
+	/// Disable softness with a value of 0.
+	float32 frequencyHz;
+
+	/// The damping ratio. 0 = no damping, 1 = critical damping.
+	float32 dampingRatio;
+};
+
+/// A weld joint essentially glues two bodies together. A weld joint may
+/// distort somewhat because the island constraint solver is approximate.
+class b2WeldJoint : public b2Joint
+{
+public:
+	b2Vec2 GetAnchorA() const;
+	b2Vec2 GetAnchorB() const;
+
+	b2Vec2 GetReactionForce(float32 inv_dt) const;
+	float32 GetReactionTorque(float32 inv_dt) const;
+
+	/// The local anchor point relative to bodyA's origin.
+	const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }
+
+	/// The local anchor point relative to bodyB's origin.
+	const b2Vec2& GetLocalAnchorB() const  { return m_localAnchorB; }
+
+	/// Get the reference angle.
+	float32 GetReferenceAngle() const { return m_referenceAngle; }
+
+	/// Set/get frequency in Hz.
+	void SetFrequency(float32 hz) { m_frequencyHz = hz; }
+	float32 GetFrequency() const { return m_frequencyHz; }
+
+	/// Set/get damping ratio.
+	void SetDampingRatio(float32 ratio) { m_dampingRatio = ratio; }
+	float32 GetDampingRatio() const { return m_dampingRatio; }
+
+	/// Dump to b2Log
+	void Dump();
+
+protected:
+
+	friend class b2Joint;
+
+	b2WeldJoint(const b2WeldJointDef* def);
+
+	void InitVelocityConstraints(const b2SolverData& data);
+	void SolveVelocityConstraints(const b2SolverData& data);
+	bool SolvePositionConstraints(const b2SolverData& data);
+
+	float32 m_frequencyHz;
+	float32 m_dampingRatio;
+	float32 m_bias;
+
+	// Solver shared
+	b2Vec2 m_localAnchorA;
+	b2Vec2 m_localAnchorB;
+	float32 m_referenceAngle;
+	float32 m_gamma;
+	b2Vec3 m_impulse;
+
+	// Solver temp
+	juce::int32 m_indexA;
+	juce::int32 m_indexB;
+	b2Vec2 m_rA;
+	b2Vec2 m_rB;
+	b2Vec2 m_localCenterA;
+	b2Vec2 m_localCenterB;
+	float32 m_invMassA;
+	float32 m_invMassB;
+	float32 m_invIA;
+	float32 m_invIB;
+	b2Mat33 m_mass;
+};
+
+#endif

modules/juce_box2d/box2d/Dynamics/Joints/b2WheelJoint.cpp

@@ -0,0 +1,419 @@
+/*
+* Copyright (c) 2006-2007 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#include "b2WheelJoint.h"
+#include "../b2Body.h"
+#include "../b2TimeStep.h"
+
+// Linear constraint (point-to-line)
+// d = pB - pA = xB + rB - xA - rA
+// C = dot(ay, d)
+// Cdot = dot(d, cross(wA, ay)) + dot(ay, vB + cross(wB, rB) - vA - cross(wA, rA))
+//      = -dot(ay, vA) - dot(cross(d + rA, ay), wA) + dot(ay, vB) + dot(cross(rB, ay), vB)
+// J = [-ay, -cross(d + rA, ay), ay, cross(rB, ay)]
+
+// Spring linear constraint
+// C = dot(ax, d)
+// Cdot = = -dot(ax, vA) - dot(cross(d + rA, ax), wA) + dot(ax, vB) + dot(cross(rB, ax), vB)
+// J = [-ax -cross(d+rA, ax) ax cross(rB, ax)]
+
+// Motor rotational constraint
+// Cdot = wB - wA
+// J = [0 0 -1 0 0 1]
+
+void b2WheelJointDef::Initialize(b2Body* bA, b2Body* bB, const b2Vec2& anchor, const b2Vec2& axis)
+{
+	bodyA = bA;
+	bodyB = bB;
+	localAnchorA = bodyA->GetLocalPoint(anchor);
+	localAnchorB = bodyB->GetLocalPoint(anchor);
+	localAxisA = bodyA->GetLocalVector(axis);
+}
+
+b2WheelJoint::b2WheelJoint(const b2WheelJointDef* def)
+: b2Joint(def)
+{
+	m_localAnchorA = def->localAnchorA;
+	m_localAnchorB = def->localAnchorB;
+	m_localXAxisA = def->localAxisA;
+	m_localYAxisA = b2Cross(1.0f, m_localXAxisA);
+
+	m_mass = 0.0f;
+	m_impulse = 0.0f;
+	m_motorMass = 0.0f;
+	m_motorImpulse = 0.0f;
+	m_springMass = 0.0f;
+	m_springImpulse = 0.0f;
+
+	m_maxMotorTorque = def->maxMotorTorque;
+	m_motorSpeed = def->motorSpeed;
+	m_enableMotor = def->enableMotor;
+
+	m_frequencyHz = def->frequencyHz;
+	m_dampingRatio = def->dampingRatio;
+
+	m_bias = 0.0f;
+	m_gamma = 0.0f;
+
+	m_ax.SetZero();
+	m_ay.SetZero();
+}
+
+void b2WheelJoint::InitVelocityConstraints(const b2SolverData& data)
+{
+	m_indexA = m_bodyA->m_islandIndex;
+	m_indexB = m_bodyB->m_islandIndex;
+	m_localCenterA = m_bodyA->m_sweep.localCenter;
+	m_localCenterB = m_bodyB->m_sweep.localCenter;
+	m_invMassA = m_bodyA->m_invMass;
+	m_invMassB = m_bodyB->m_invMass;
+	m_invIA = m_bodyA->m_invI;
+	m_invIB = m_bodyB->m_invI;
+
+	float32 mA = m_invMassA, mB = m_invMassB;
+	float32 iA = m_invIA, iB = m_invIB;
+
+	b2Vec2 cA = data.positions[m_indexA].c;
+	float32 aA = data.positions[m_indexA].a;
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float32 wA = data.velocities[m_indexA].w;
+
+	b2Vec2 cB = data.positions[m_indexB].c;
+	float32 aB = data.positions[m_indexB].a;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	b2Rot qA(aA), qB(aB);
+
+	// Compute the effective masses.
+	b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
+	b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
+	b2Vec2 d = cB + rB - cA - rA;
+
+	// Point to line constraint
+	{
+		m_ay = b2Mul(qA, m_localYAxisA);
+		m_sAy = b2Cross(d + rA, m_ay);
+		m_sBy = b2Cross(rB, m_ay);
+
+		m_mass = mA + mB + iA * m_sAy * m_sAy + iB * m_sBy * m_sBy;
+
+		if (m_mass > 0.0f)
+		{
+			m_mass = 1.0f / m_mass;
+		}
+	}
+
+	// Spring constraint
+	m_springMass = 0.0f;
+	m_bias = 0.0f;
+	m_gamma = 0.0f;
+	if (m_frequencyHz > 0.0f)
+	{
+		m_ax = b2Mul(qA, m_localXAxisA);
+		m_sAx = b2Cross(d + rA, m_ax);
+		m_sBx = b2Cross(rB, m_ax);
+
+		float32 invMass = mA + mB + iA * m_sAx * m_sAx + iB * m_sBx * m_sBx;
+
+		if (invMass > 0.0f)
+		{
+			m_springMass = 1.0f / invMass;
+
+			float32 C = b2Dot(d, m_ax);
+
+			// Frequency
+			float32 omega = 2.0f * b2_pi * m_frequencyHz;
+
+			// Damping coefficient
+			float32 damp = 2.0f * m_springMass * m_dampingRatio * omega;
+
+			// Spring stiffness
+			float32 k = m_springMass * omega * omega;
+
+			// magic formulas
+			float32 h = data.step.dt;
+			m_gamma = h * (damp + h * k);
+			if (m_gamma > 0.0f)
+			{
+				m_gamma = 1.0f / m_gamma;
+			}
+
+			m_bias = C * h * k * m_gamma;
+
+			m_springMass = invMass + m_gamma;
+			if (m_springMass > 0.0f)
+			{
+				m_springMass = 1.0f / m_springMass;
+			}
+		}
+	}
+	else
+	{
+		m_springImpulse = 0.0f;
+	}
+
+	// Rotational motor
+	if (m_enableMotor)
+	{
+		m_motorMass = iA + iB;
+		if (m_motorMass > 0.0f)
+		{
+			m_motorMass = 1.0f / m_motorMass;
+		}
+	}
+	else
+	{
+		m_motorMass = 0.0f;
+		m_motorImpulse = 0.0f;
+	}
+
+	if (data.step.warmStarting)
+	{
+		// Account for variable time step.
+		m_impulse *= data.step.dtRatio;
+		m_springImpulse *= data.step.dtRatio;
+		m_motorImpulse *= data.step.dtRatio;
+
+		b2Vec2 P = m_impulse * m_ay + m_springImpulse * m_ax;
+		float32 LA = m_impulse * m_sAy + m_springImpulse * m_sAx + m_motorImpulse;
+		float32 LB = m_impulse * m_sBy + m_springImpulse * m_sBx + m_motorImpulse;
+
+		vA -= m_invMassA * P;
+		wA -= m_invIA * LA;
+
+		vB += m_invMassB * P;
+		wB += m_invIB * LB;
+	}
+	else
+	{
+		m_impulse = 0.0f;
+		m_springImpulse = 0.0f;
+		m_motorImpulse = 0.0f;
+	}
+
+	data.velocities[m_indexA].v = vA;
+	data.velocities[m_indexA].w = wA;
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+}
+
+void b2WheelJoint::SolveVelocityConstraints(const b2SolverData& data)
+{
+	float32 mA = m_invMassA, mB = m_invMassB;
+	float32 iA = m_invIA, iB = m_invIB;
+
+	b2Vec2 vA = data.velocities[m_indexA].v;
+	float32 wA = data.velocities[m_indexA].w;
+	b2Vec2 vB = data.velocities[m_indexB].v;
+	float32 wB = data.velocities[m_indexB].w;
+
+	// Solve spring constraint
+	{
+		float32 Cdot = b2Dot(m_ax, vB - vA) + m_sBx * wB - m_sAx * wA;
+		float32 impulse = -m_springMass * (Cdot + m_bias + m_gamma * m_springImpulse);
+		m_springImpulse += impulse;
+
+		b2Vec2 P = impulse * m_ax;
+		float32 LA = impulse * m_sAx;
+		float32 LB = impulse * m_sBx;
+
+		vA -= mA * P;
+		wA -= iA * LA;
+
+		vB += mB * P;
+		wB += iB * LB;
+	}
+
+	// Solve rotational motor constraint
+	{
+		float32 Cdot = wB - wA - m_motorSpeed;
+		float32 impulse = -m_motorMass * Cdot;
+
+		float32 oldImpulse = m_motorImpulse;
+		float32 maxImpulse = data.step.dt * m_maxMotorTorque;
+		m_motorImpulse = b2Clamp(m_motorImpulse + impulse, -maxImpulse, maxImpulse);
+		impulse = m_motorImpulse - oldImpulse;
+
+		wA -= iA * impulse;
+		wB += iB * impulse;
+	}
+
+	// Solve point to line constraint
+	{
+		float32 Cdot = b2Dot(m_ay, vB - vA) + m_sBy * wB - m_sAy * wA;
+		float32 impulse = -m_mass * Cdot;
+		m_impulse += impulse;
+
+		b2Vec2 P = impulse * m_ay;
+		float32 LA = impulse * m_sAy;
+		float32 LB = impulse * m_sBy;
+
+		vA -= mA * P;
+		wA -= iA * LA;
+
+		vB += mB * P;
+		wB += iB * LB;
+	}
+
+	data.velocities[m_indexA].v = vA;
+	data.velocities[m_indexA].w = wA;
+	data.velocities[m_indexB].v = vB;
+	data.velocities[m_indexB].w = wB;
+}
+
+bool b2WheelJoint::SolvePositionConstraints(const b2SolverData& data)
+{
+	b2Vec2 cA = data.positions[m_indexA].c;
+	float32 aA = data.positions[m_indexA].a;
+	b2Vec2 cB = data.positions[m_indexB].c;
+	float32 aB = data.positions[m_indexB].a;
+
+	b2Rot qA(aA), qB(aB);
+
+	b2Vec2 rA = b2Mul(qA, m_localAnchorA - m_localCenterA);
+	b2Vec2 rB = b2Mul(qB, m_localAnchorB - m_localCenterB);
+	b2Vec2 d = (cB - cA) + rB - rA;
+
+	b2Vec2 ay = b2Mul(qA, m_localYAxisA);
+
+	float32 sAy = b2Cross(d + rA, ay);
+	float32 sBy = b2Cross(rB, ay);
+
+	float32 C = b2Dot(d, ay);
+
+	float32 k = m_invMassA + m_invMassB + m_invIA * m_sAy * m_sAy + m_invIB * m_sBy * m_sBy;
+
+	float32 impulse;
+	if (k != 0.0f)
+	{
+		impulse = - C / k;
+	}
+	else
+	{
+		impulse = 0.0f;
+	}
+
+	b2Vec2 P = impulse * ay;
+	float32 LA = impulse * sAy;
+	float32 LB = impulse * sBy;
+
+	cA -= m_invMassA * P;
+	aA -= m_invIA * LA;
+	cB += m_invMassB * P;
+	aB += m_invIB * LB;
+
+	data.positions[m_indexA].c = cA;
+	data.positions[m_indexA].a = aA;
+	data.positions[m_indexB].c = cB;
+	data.positions[m_indexB].a = aB;
+
+	return b2Abs(C) <= b2_linearSlop;
+}
+
+b2Vec2 b2WheelJoint::GetAnchorA() const
+{
+	return m_bodyA->GetWorldPoint(m_localAnchorA);
+}
+
+b2Vec2 b2WheelJoint::GetAnchorB() const
+{
+	return m_bodyB->GetWorldPoint(m_localAnchorB);
+}
+
+b2Vec2 b2WheelJoint::GetReactionForce(float32 inv_dt) const
+{
+	return inv_dt * (m_impulse * m_ay + m_springImpulse * m_ax);
+}
+
+float32 b2WheelJoint::GetReactionTorque(float32 inv_dt) const
+{
+	return inv_dt * m_motorImpulse;
+}
+
+float32 b2WheelJoint::GetJointTranslation() const
+{
+	b2Body* bA = m_bodyA;
+	b2Body* bB = m_bodyB;
+
+	b2Vec2 pA = bA->GetWorldPoint(m_localAnchorA);
+	b2Vec2 pB = bB->GetWorldPoint(m_localAnchorB);
+	b2Vec2 d = pB - pA;
+	b2Vec2 axis = bA->GetWorldVector(m_localXAxisA);
+
+	float32 translation = b2Dot(d, axis);
+	return translation;
+}
+
+float32 b2WheelJoint::GetJointSpeed() const
+{
+	float32 wA = m_bodyA->m_angularVelocity;
+	float32 wB = m_bodyB->m_angularVelocity;
+	return wB - wA;
+}
+
+bool b2WheelJoint::IsMotorEnabled() const
+{
+	return m_enableMotor;
+}
+
+void b2WheelJoint::EnableMotor(bool flag)
+{
+	m_bodyA->SetAwake(true);
+	m_bodyB->SetAwake(true);
+	m_enableMotor = flag;
+}
+
+void b2WheelJoint::SetMotorSpeed(float32 speed)
+{
+	m_bodyA->SetAwake(true);
+	m_bodyB->SetAwake(true);
+	m_motorSpeed = speed;
+}
+
+void b2WheelJoint::SetMaxMotorTorque(float32 torque)
+{
+	m_bodyA->SetAwake(true);
+	m_bodyB->SetAwake(true);
+	m_maxMotorTorque = torque;
+}
+
+float32 b2WheelJoint::GetMotorTorque(float32 inv_dt) const
+{
+	return inv_dt * m_motorImpulse;
+}
+
+void b2WheelJoint::Dump()
+{
+	int32 indexA = m_bodyA->m_islandIndex;
+	int32 indexB = m_bodyB->m_islandIndex;
+
+	b2Log("  b2WheelJointDef jd;\n");
+	b2Log("  jd.bodyA = bodies[%d];\n", indexA);
+	b2Log("  jd.bodyB = bodies[%d];\n", indexB);
+	b2Log("  jd.collideConnected = bool(%d);\n", m_collideConnected);
+	b2Log("  jd.localAnchorA.Set(%.15lef, %.15lef);\n", m_localAnchorA.x, m_localAnchorA.y);
+	b2Log("  jd.localAnchorB.Set(%.15lef, %.15lef);\n", m_localAnchorB.x, m_localAnchorB.y);
+	b2Log("  jd.localAxisA.Set(%.15lef, %.15lef);\n", m_localXAxisA.x, m_localXAxisA.y);
+	b2Log("  jd.enableMotor = bool(%d);\n", m_enableMotor);
+	b2Log("  jd.motorSpeed = %.15lef;\n", m_motorSpeed);
+	b2Log("  jd.maxMotorTorque = %.15lef;\n", m_maxMotorTorque);
+	b2Log("  jd.frequencyHz = %.15lef;\n", m_frequencyHz);
+	b2Log("  jd.dampingRatio = %.15lef;\n", m_dampingRatio);
+	b2Log("  joints[%d] = m_world->CreateJoint(&jd);\n", m_index);
+}

modules/juce_box2d/box2d/Dynamics/Joints/b2WheelJoint.h

@@ -0,0 +1,213 @@
+/*
+* Copyright (c) 2006-2011 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#ifndef B2_WHEEL_JOINT_H
+#define B2_WHEEL_JOINT_H
+
+#include "b2Joint.h"
+
+/// Wheel joint definition. This requires defining a line of
+/// motion using an axis and an anchor point. The definition uses local
+/// anchor points and a local axis so that the initial configuration
+/// can violate the constraint slightly. The joint translation is zero
+/// when the local anchor points coincide in world space. Using local
+/// anchors and a local axis helps when saving and loading a game.
+struct b2WheelJointDef : public b2JointDef
+{
+	b2WheelJointDef()
+	{
+		type = e_wheelJoint;
+		localAnchorA.SetZero();
+		localAnchorB.SetZero();
+		localAxisA.Set(1.0f, 0.0f);
+		enableMotor = false;
+		maxMotorTorque = 0.0f;
+		motorSpeed = 0.0f;
+		frequencyHz = 2.0f;
+		dampingRatio = 0.7f;
+	}
+
+	/// Initialize the bodies, anchors, axis, and reference angle using the world
+	/// anchor and world axis.
+	void Initialize(b2Body* bodyA, b2Body* bodyB, const b2Vec2& anchor, const b2Vec2& axis);
+
+	/// The local anchor point relative to bodyA's origin.
+	b2Vec2 localAnchorA;
+
+	/// The local anchor point relative to bodyB's origin.
+	b2Vec2 localAnchorB;
+
+	/// The local translation axis in bodyA.
+	b2Vec2 localAxisA;
+
+	/// Enable/disable the joint motor.
+	bool enableMotor;
+
+	/// The maximum motor torque, usually in N-m.
+	float32 maxMotorTorque;
+
+	/// The desired motor speed in radians per second.
+	float32 motorSpeed;
+
+	/// Suspension frequency, zero indicates no suspension
+	float32 frequencyHz;
+
+	/// Suspension damping ratio, one indicates critical damping
+	float32 dampingRatio;
+};
+
+/// A wheel joint. This joint provides two degrees of freedom: translation
+/// along an axis fixed in bodyA and rotation in the plane. You can use a
+/// joint limit to restrict the range of motion and a joint motor to drive
+/// the rotation or to model rotational friction.
+/// This joint is designed for vehicle suspensions.
+class b2WheelJoint : public b2Joint
+{
+public:
+	void GetDefinition(b2WheelJointDef* def) const;
+
+	b2Vec2 GetAnchorA() const;
+	b2Vec2 GetAnchorB() const;
+
+	b2Vec2 GetReactionForce(float32 inv_dt) const;
+	float32 GetReactionTorque(float32 inv_dt) const;
+
+	/// The local anchor point relative to bodyA's origin.
+	const b2Vec2& GetLocalAnchorA() const { return m_localAnchorA; }
+
+	/// The local anchor point relative to bodyB's origin.
+	const b2Vec2& GetLocalAnchorB() const  { return m_localAnchorB; }
+
+	/// The local joint axis relative to bodyA.
+	const b2Vec2& GetLocalAxisA() const { return m_localXAxisA; }
+
+	/// Get the current joint translation, usually in meters.
+	float32 GetJointTranslation() const;
+
+	/// Get the current joint translation speed, usually in meters per second.
+	float32 GetJointSpeed() const;
+
+	/// Is the joint motor enabled?
+	bool IsMotorEnabled() const;
+
+	/// Enable/disable the joint motor.
+	void EnableMotor(bool flag);
+
+	/// Set the motor speed, usually in radians per second.
+	void SetMotorSpeed(float32 speed);
+
+	/// Get the motor speed, usually in radians per second.
+	float32 GetMotorSpeed() const;
+
+	/// Set/Get the maximum motor force, usually in N-m.
+	void SetMaxMotorTorque(float32 torque);
+	float32 GetMaxMotorTorque() const;
+
+	/// Get the current motor torque given the inverse time step, usually in N-m.
+	float32 GetMotorTorque(float32 inv_dt) const;
+
+	/// Set/Get the spring frequency in hertz. Setting the frequency to zero disables the spring.
+	void SetSpringFrequencyHz(float32 hz);
+	float32 GetSpringFrequencyHz() const;
+
+	/// Set/Get the spring damping ratio
+	void SetSpringDampingRatio(float32 ratio);
+	float32 GetSpringDampingRatio() const;
+
+	/// Dump to b2Log
+	void Dump();
+
+protected:
+
+	friend class b2Joint;
+	b2WheelJoint(const b2WheelJointDef* def);
+
+	void InitVelocityConstraints(const b2SolverData& data);
+	void SolveVelocityConstraints(const b2SolverData& data);
+	bool SolvePositionConstraints(const b2SolverData& data);
+
+	float32 m_frequencyHz;
+	float32 m_dampingRatio;
+
+	// Solver shared
+	b2Vec2 m_localAnchorA;
+	b2Vec2 m_localAnchorB;
+	b2Vec2 m_localXAxisA;
+	b2Vec2 m_localYAxisA;
+
+	float32 m_impulse;
+	float32 m_motorImpulse;
+	float32 m_springImpulse;
+
+	float32 m_maxMotorTorque;
+	float32 m_motorSpeed;
+	bool m_enableMotor;
+
+	// Solver temp
+	juce::int32 m_indexA;
+	juce::int32 m_indexB;
+	b2Vec2 m_localCenterA;
+	b2Vec2 m_localCenterB;
+	float32 m_invMassA;
+	float32 m_invMassB;
+	float32 m_invIA;
+	float32 m_invIB;
+
+	b2Vec2 m_ax, m_ay;
+	float32 m_sAx, m_sBx;
+	float32 m_sAy, m_sBy;
+
+	float32 m_mass;
+	float32 m_motorMass;
+	float32 m_springMass;
+
+	float32 m_bias;
+	float32 m_gamma;
+};
+
+inline float32 b2WheelJoint::GetMotorSpeed() const
+{
+	return m_motorSpeed;
+}
+
+inline float32 b2WheelJoint::GetMaxMotorTorque() const
+{
+	return m_maxMotorTorque;
+}
+
+inline void b2WheelJoint::SetSpringFrequencyHz(float32 hz)
+{
+	m_frequencyHz = hz;
+}
+
+inline float32 b2WheelJoint::GetSpringFrequencyHz() const
+{
+	return m_frequencyHz;
+}
+
+inline void b2WheelJoint::SetSpringDampingRatio(float32 ratio)
+{
+	m_dampingRatio = ratio;
+}
+
+inline float32 b2WheelJoint::GetSpringDampingRatio() const
+{
+	return m_dampingRatio;
+}
+
+#endif