170 lines
4.6 KiB
C++
170 lines
4.6 KiB
C++
/*
|
|
* 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
|