699 lines
16 KiB
C++
699 lines
16 KiB
C++
/*
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* Copyright (c) 2007-2009 Erin Catto http://www.box2d.org
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*
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* This software is provided 'as-is', without any express or implied
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* warranty. In no event will the authors be held liable for any damages
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* arising from the use of this software.
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* Permission is granted to anyone to use this software for any purpose,
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* including commercial applications, and to alter it and redistribute it
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* freely, subject to the following restrictions:
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* 1. The origin of this software must not be misrepresented; you must not
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* claim that you wrote the original software. If you use this software
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* in a product, an acknowledgment in the product documentation would be
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* appreciated but is not required.
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* 2. Altered source versions must be plainly marked as such, and must not be
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* misrepresented as being the original software.
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* 3. This notice may not be removed or altered from any source distribution.
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*/
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#include "b2Collision.h"
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#include "Shapes/b2CircleShape.h"
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#include "Shapes/b2EdgeShape.h"
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#include "Shapes/b2PolygonShape.h"
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// Compute contact points for edge versus circle.
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// This accounts for edge connectivity.
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void b2CollideEdgeAndCircle(b2Manifold* manifold,
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const b2EdgeShape* edgeA, const b2Transform& xfA,
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const b2CircleShape* circleB, const b2Transform& xfB)
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{
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manifold->pointCount = 0;
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// Compute circle in frame of edge
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b2Vec2 Q = b2MulT(xfA, b2Mul(xfB, circleB->m_p));
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b2Vec2 A = edgeA->m_vertex1, B = edgeA->m_vertex2;
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b2Vec2 e = B - A;
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// Barycentric coordinates
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float32 u = b2Dot(e, B - Q);
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float32 v = b2Dot(e, Q - A);
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float32 radius = edgeA->m_radius + circleB->m_radius;
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b2ContactFeature cf;
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cf.indexB = 0;
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cf.typeB = b2ContactFeature::e_vertex;
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// Region A
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if (v <= 0.0f)
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{
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b2Vec2 P = A;
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b2Vec2 d = Q - P;
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float32 dd = b2Dot(d, d);
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if (dd > radius * radius)
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{
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return;
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}
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// Is there an edge connected to A?
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if (edgeA->m_hasVertex0)
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{
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b2Vec2 A1 = edgeA->m_vertex0;
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b2Vec2 B1 = A;
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b2Vec2 e1 = B1 - A1;
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float32 u1 = b2Dot(e1, B1 - Q);
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// Is the circle in Region AB of the previous edge?
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if (u1 > 0.0f)
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{
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return;
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}
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}
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cf.indexA = 0;
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cf.typeA = b2ContactFeature::e_vertex;
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manifold->pointCount = 1;
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manifold->type = b2Manifold::e_circles;
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manifold->localNormal.SetZero();
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manifold->localPoint = P;
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manifold->points[0].id.key = 0;
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manifold->points[0].id.cf = cf;
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manifold->points[0].localPoint = circleB->m_p;
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return;
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}
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// Region B
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if (u <= 0.0f)
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{
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b2Vec2 P = B;
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b2Vec2 d = Q - P;
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float32 dd = b2Dot(d, d);
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if (dd > radius * radius)
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{
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return;
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}
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// Is there an edge connected to B?
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if (edgeA->m_hasVertex3)
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{
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b2Vec2 B2 = edgeA->m_vertex3;
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b2Vec2 A2 = B;
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b2Vec2 e2 = B2 - A2;
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float32 v2 = b2Dot(e2, Q - A2);
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// Is the circle in Region AB of the next edge?
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if (v2 > 0.0f)
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{
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return;
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}
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}
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cf.indexA = 1;
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cf.typeA = b2ContactFeature::e_vertex;
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manifold->pointCount = 1;
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manifold->type = b2Manifold::e_circles;
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manifold->localNormal.SetZero();
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manifold->localPoint = P;
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manifold->points[0].id.key = 0;
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manifold->points[0].id.cf = cf;
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manifold->points[0].localPoint = circleB->m_p;
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return;
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}
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// Region AB
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float32 den = b2Dot(e, e);
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b2Assert(den > 0.0f);
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b2Vec2 P = (1.0f / den) * (u * A + v * B);
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b2Vec2 d = Q - P;
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float32 dd = b2Dot(d, d);
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if (dd > radius * radius)
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{
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return;
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}
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b2Vec2 n(-e.y, e.x);
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if (b2Dot(n, Q - A) < 0.0f)
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{
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n.Set(-n.x, -n.y);
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}
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n.Normalize();
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cf.indexA = 0;
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cf.typeA = b2ContactFeature::e_face;
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manifold->pointCount = 1;
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manifold->type = b2Manifold::e_faceA;
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manifold->localNormal = n;
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manifold->localPoint = A;
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manifold->points[0].id.key = 0;
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manifold->points[0].id.cf = cf;
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manifold->points[0].localPoint = circleB->m_p;
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}
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// This structure is used to keep track of the best separating axis.
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struct b2EPAxis
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{
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enum Type
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{
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e_unknown,
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e_edgeA,
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e_edgeB
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};
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Type type;
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int32 index;
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float32 separation;
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};
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// This holds polygon B expressed in frame A.
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struct b2TempPolygon
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{
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b2Vec2 vertices[b2_maxPolygonVertices];
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b2Vec2 normals[b2_maxPolygonVertices];
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int32 count;
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};
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// Reference face used for clipping
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struct b2ReferenceFace
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{
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int32 i1, i2;
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b2Vec2 v1, v2;
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b2Vec2 normal;
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b2Vec2 sideNormal1;
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float32 sideOffset1;
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b2Vec2 sideNormal2;
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float32 sideOffset2;
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};
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// This class collides and edge and a polygon, taking into account edge adjacency.
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struct b2EPCollider
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{
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void Collide(b2Manifold* manifold, const b2EdgeShape* edgeA, const b2Transform& xfA,
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const b2PolygonShape* polygonB, const b2Transform& xfB);
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b2EPAxis ComputeEdgeSeparation();
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b2EPAxis ComputePolygonSeparation();
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enum VertexType
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{
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e_isolated,
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e_concave,
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e_convex
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};
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b2TempPolygon m_polygonB;
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b2Transform m_xf;
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b2Vec2 m_centroidB;
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b2Vec2 m_v0, m_v1, m_v2, m_v3;
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b2Vec2 m_normal0, m_normal1, m_normal2;
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b2Vec2 m_normal;
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VertexType m_type1, m_type2;
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b2Vec2 m_lowerLimit, m_upperLimit;
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float32 m_radius;
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bool m_front;
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};
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// Algorithm:
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// 1. Classify v1 and v2
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// 2. Classify polygon centroid as front or back
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// 3. Flip normal if necessary
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// 4. Initialize normal range to [-pi, pi] about face normal
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// 5. Adjust normal range according to adjacent edges
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// 6. Visit each separating axes, only accept axes within the range
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// 7. Return if _any_ axis indicates separation
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// 8. Clip
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void b2EPCollider::Collide(b2Manifold* manifold, const b2EdgeShape* edgeA, const b2Transform& xfA,
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const b2PolygonShape* polygonB, const b2Transform& xfB)
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{
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m_xf = b2MulT(xfA, xfB);
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m_centroidB = b2Mul(m_xf, polygonB->m_centroid);
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m_v0 = edgeA->m_vertex0;
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m_v1 = edgeA->m_vertex1;
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m_v2 = edgeA->m_vertex2;
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m_v3 = edgeA->m_vertex3;
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bool hasVertex0 = edgeA->m_hasVertex0;
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bool hasVertex3 = edgeA->m_hasVertex3;
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b2Vec2 edge1 = m_v2 - m_v1;
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edge1.Normalize();
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m_normal1.Set(edge1.y, -edge1.x);
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float32 offset1 = b2Dot(m_normal1, m_centroidB - m_v1);
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float32 offset0 = 0.0f, offset2 = 0.0f;
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bool convex1 = false, convex2 = false;
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// Is there a preceding edge?
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if (hasVertex0)
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{
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b2Vec2 edge0 = m_v1 - m_v0;
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edge0.Normalize();
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m_normal0.Set(edge0.y, -edge0.x);
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convex1 = b2Cross(edge0, edge1) >= 0.0f;
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offset0 = b2Dot(m_normal0, m_centroidB - m_v0);
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}
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// Is there a following edge?
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if (hasVertex3)
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{
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b2Vec2 edge2 = m_v3 - m_v2;
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edge2.Normalize();
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m_normal2.Set(edge2.y, -edge2.x);
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convex2 = b2Cross(edge1, edge2) > 0.0f;
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offset2 = b2Dot(m_normal2, m_centroidB - m_v2);
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}
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// Determine front or back collision. Determine collision normal limits.
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if (hasVertex0 && hasVertex3)
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{
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if (convex1 && convex2)
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{
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m_front = offset0 >= 0.0f || offset1 >= 0.0f || offset2 >= 0.0f;
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if (m_front)
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{
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m_normal = m_normal1;
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m_lowerLimit = m_normal0;
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m_upperLimit = m_normal2;
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}
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else
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{
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m_normal = -m_normal1;
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m_lowerLimit = -m_normal1;
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m_upperLimit = -m_normal1;
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}
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}
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else if (convex1)
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{
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m_front = offset0 >= 0.0f || (offset1 >= 0.0f && offset2 >= 0.0f);
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if (m_front)
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{
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m_normal = m_normal1;
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m_lowerLimit = m_normal0;
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m_upperLimit = m_normal1;
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}
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else
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{
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m_normal = -m_normal1;
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m_lowerLimit = -m_normal2;
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m_upperLimit = -m_normal1;
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}
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}
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else if (convex2)
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{
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m_front = offset2 >= 0.0f || (offset0 >= 0.0f && offset1 >= 0.0f);
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if (m_front)
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{
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m_normal = m_normal1;
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m_lowerLimit = m_normal1;
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m_upperLimit = m_normal2;
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}
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else
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{
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m_normal = -m_normal1;
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m_lowerLimit = -m_normal1;
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m_upperLimit = -m_normal0;
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}
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}
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else
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{
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m_front = offset0 >= 0.0f && offset1 >= 0.0f && offset2 >= 0.0f;
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if (m_front)
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{
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m_normal = m_normal1;
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m_lowerLimit = m_normal1;
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m_upperLimit = m_normal1;
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}
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else
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{
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m_normal = -m_normal1;
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m_lowerLimit = -m_normal2;
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m_upperLimit = -m_normal0;
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}
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}
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}
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else if (hasVertex0)
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{
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if (convex1)
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{
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m_front = offset0 >= 0.0f || offset1 >= 0.0f;
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if (m_front)
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{
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m_normal = m_normal1;
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m_lowerLimit = m_normal0;
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m_upperLimit = -m_normal1;
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}
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else
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{
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m_normal = -m_normal1;
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m_lowerLimit = m_normal1;
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m_upperLimit = -m_normal1;
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}
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}
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else
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{
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m_front = offset0 >= 0.0f && offset1 >= 0.0f;
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if (m_front)
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{
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m_normal = m_normal1;
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m_lowerLimit = m_normal1;
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m_upperLimit = -m_normal1;
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}
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else
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{
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m_normal = -m_normal1;
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m_lowerLimit = m_normal1;
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m_upperLimit = -m_normal0;
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}
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}
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}
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else if (hasVertex3)
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{
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if (convex2)
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{
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m_front = offset1 >= 0.0f || offset2 >= 0.0f;
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if (m_front)
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{
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m_normal = m_normal1;
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m_lowerLimit = -m_normal1;
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m_upperLimit = m_normal2;
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}
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else
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{
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m_normal = -m_normal1;
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m_lowerLimit = -m_normal1;
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m_upperLimit = m_normal1;
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}
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}
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else
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{
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m_front = offset1 >= 0.0f && offset2 >= 0.0f;
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if (m_front)
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{
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m_normal = m_normal1;
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m_lowerLimit = -m_normal1;
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m_upperLimit = m_normal1;
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}
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else
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{
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m_normal = -m_normal1;
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m_lowerLimit = -m_normal2;
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m_upperLimit = m_normal1;
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}
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}
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}
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else
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{
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m_front = offset1 >= 0.0f;
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if (m_front)
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{
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m_normal = m_normal1;
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m_lowerLimit = -m_normal1;
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m_upperLimit = -m_normal1;
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}
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else
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{
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m_normal = -m_normal1;
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m_lowerLimit = m_normal1;
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m_upperLimit = m_normal1;
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}
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}
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// Get polygonB in frameA
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m_polygonB.count = polygonB->m_vertexCount;
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for (int32 i = 0; i < polygonB->m_vertexCount; ++i)
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{
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m_polygonB.vertices[i] = b2Mul(m_xf, polygonB->m_vertices[i]);
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m_polygonB.normals[i] = b2Mul(m_xf.q, polygonB->m_normals[i]);
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}
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m_radius = 2.0f * b2_polygonRadius;
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manifold->pointCount = 0;
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b2EPAxis edgeAxis = ComputeEdgeSeparation();
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// If no valid normal can be found than this edge should not collide.
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if (edgeAxis.type == b2EPAxis::e_unknown)
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{
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return;
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}
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if (edgeAxis.separation > m_radius)
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{
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return;
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}
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b2EPAxis polygonAxis = ComputePolygonSeparation();
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if (polygonAxis.type != b2EPAxis::e_unknown && polygonAxis.separation > m_radius)
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{
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return;
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}
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// Use hysteresis for jitter reduction.
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const float32 k_relativeTol = 0.98f;
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const float32 k_absoluteTol = 0.001f;
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b2EPAxis primaryAxis;
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if (polygonAxis.type == b2EPAxis::e_unknown)
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{
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primaryAxis = edgeAxis;
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}
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else if (polygonAxis.separation > k_relativeTol * edgeAxis.separation + k_absoluteTol)
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{
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primaryAxis = polygonAxis;
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}
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else
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{
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primaryAxis = edgeAxis;
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}
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b2ClipVertex ie[2];
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b2ReferenceFace rf;
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if (primaryAxis.type == b2EPAxis::e_edgeA)
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{
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manifold->type = b2Manifold::e_faceA;
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// Search for the polygon normal that is most anti-parallel to the edge normal.
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int32 bestIndex = 0;
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float32 bestValue = b2Dot(m_normal, m_polygonB.normals[0]);
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for (int32 i = 1; i < m_polygonB.count; ++i)
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{
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float32 value = b2Dot(m_normal, m_polygonB.normals[i]);
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if (value < bestValue)
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{
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bestValue = value;
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bestIndex = i;
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}
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}
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int32 i1 = bestIndex;
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int32 i2 = i1 + 1 < m_polygonB.count ? i1 + 1 : 0;
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ie[0].v = m_polygonB.vertices[i1];
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ie[0].id.cf.indexA = 0;
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ie[0].id.cf.indexB = (uint8) i1;
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ie[0].id.cf.typeA = b2ContactFeature::e_face;
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ie[0].id.cf.typeB = b2ContactFeature::e_vertex;
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ie[1].v = m_polygonB.vertices[i2];
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ie[1].id.cf.indexA = 0;
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ie[1].id.cf.indexB = (uint8) i2;
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ie[1].id.cf.typeA = b2ContactFeature::e_face;
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ie[1].id.cf.typeB = b2ContactFeature::e_vertex;
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if (m_front)
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{
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rf.i1 = 0;
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rf.i2 = 1;
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rf.v1 = m_v1;
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rf.v2 = m_v2;
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rf.normal = m_normal1;
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}
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else
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{
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rf.i1 = 1;
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rf.i2 = 0;
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rf.v1 = m_v2;
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rf.v2 = m_v1;
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rf.normal = -m_normal1;
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}
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}
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else
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{
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manifold->type = b2Manifold::e_faceB;
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ie[0].v = m_v1;
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ie[0].id.cf.indexA = 0;
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ie[0].id.cf.indexB = (uint8) primaryAxis.index;
|
|
ie[0].id.cf.typeA = b2ContactFeature::e_vertex;
|
|
ie[0].id.cf.typeB = b2ContactFeature::e_face;
|
|
|
|
ie[1].v = m_v2;
|
|
ie[1].id.cf.indexA = 0;
|
|
ie[1].id.cf.indexB = (uint8) primaryAxis.index;
|
|
ie[1].id.cf.typeA = b2ContactFeature::e_vertex;
|
|
ie[1].id.cf.typeB = b2ContactFeature::e_face;
|
|
|
|
rf.i1 = primaryAxis.index;
|
|
rf.i2 = rf.i1 + 1 < m_polygonB.count ? rf.i1 + 1 : 0;
|
|
rf.v1 = m_polygonB.vertices[rf.i1];
|
|
rf.v2 = m_polygonB.vertices[rf.i2];
|
|
rf.normal = m_polygonB.normals[rf.i1];
|
|
}
|
|
|
|
rf.sideNormal1.Set(rf.normal.y, -rf.normal.x);
|
|
rf.sideNormal2 = -rf.sideNormal1;
|
|
rf.sideOffset1 = b2Dot(rf.sideNormal1, rf.v1);
|
|
rf.sideOffset2 = b2Dot(rf.sideNormal2, rf.v2);
|
|
|
|
// Clip incident edge against extruded edge1 side edges.
|
|
b2ClipVertex clipPoints1[2];
|
|
b2ClipVertex clipPoints2[2];
|
|
int32 np;
|
|
|
|
// Clip to box side 1
|
|
np = b2ClipSegmentToLine(clipPoints1, ie, rf.sideNormal1, rf.sideOffset1, rf.i1);
|
|
|
|
if (np < b2_maxManifoldPoints)
|
|
{
|
|
return;
|
|
}
|
|
|
|
// Clip to negative box side 1
|
|
np = b2ClipSegmentToLine(clipPoints2, clipPoints1, rf.sideNormal2, rf.sideOffset2, rf.i2);
|
|
|
|
if (np < b2_maxManifoldPoints)
|
|
{
|
|
return;
|
|
}
|
|
|
|
// Now clipPoints2 contains the clipped points.
|
|
if (primaryAxis.type == b2EPAxis::e_edgeA)
|
|
{
|
|
manifold->localNormal = rf.normal;
|
|
manifold->localPoint = rf.v1;
|
|
}
|
|
else
|
|
{
|
|
manifold->localNormal = polygonB->m_normals[rf.i1];
|
|
manifold->localPoint = polygonB->m_vertices[rf.i1];
|
|
}
|
|
|
|
int32 pointCount = 0;
|
|
for (int32 i = 0; i < b2_maxManifoldPoints; ++i)
|
|
{
|
|
float32 separation;
|
|
|
|
separation = b2Dot(rf.normal, clipPoints2[i].v - rf.v1);
|
|
|
|
if (separation <= m_radius)
|
|
{
|
|
b2ManifoldPoint* cp = manifold->points + pointCount;
|
|
|
|
if (primaryAxis.type == b2EPAxis::e_edgeA)
|
|
{
|
|
cp->localPoint = b2MulT(m_xf, clipPoints2[i].v);
|
|
cp->id = clipPoints2[i].id;
|
|
}
|
|
else
|
|
{
|
|
cp->localPoint = clipPoints2[i].v;
|
|
cp->id.cf.typeA = clipPoints2[i].id.cf.typeB;
|
|
cp->id.cf.typeB = clipPoints2[i].id.cf.typeA;
|
|
cp->id.cf.indexA = clipPoints2[i].id.cf.indexB;
|
|
cp->id.cf.indexB = clipPoints2[i].id.cf.indexA;
|
|
}
|
|
|
|
++pointCount;
|
|
}
|
|
}
|
|
|
|
manifold->pointCount = pointCount;
|
|
}
|
|
|
|
b2EPAxis b2EPCollider::ComputeEdgeSeparation()
|
|
{
|
|
b2EPAxis axis;
|
|
axis.type = b2EPAxis::e_edgeA;
|
|
axis.index = m_front ? 0 : 1;
|
|
axis.separation = FLT_MAX;
|
|
|
|
for (int32 i = 0; i < m_polygonB.count; ++i)
|
|
{
|
|
float32 s = b2Dot(m_normal, m_polygonB.vertices[i] - m_v1);
|
|
if (s < axis.separation)
|
|
{
|
|
axis.separation = s;
|
|
}
|
|
}
|
|
|
|
return axis;
|
|
}
|
|
|
|
b2EPAxis b2EPCollider::ComputePolygonSeparation()
|
|
{
|
|
b2EPAxis axis;
|
|
axis.type = b2EPAxis::e_unknown;
|
|
axis.index = -1;
|
|
axis.separation = -FLT_MAX;
|
|
|
|
b2Vec2 perp(-m_normal.y, m_normal.x);
|
|
|
|
for (int32 i = 0; i < m_polygonB.count; ++i)
|
|
{
|
|
b2Vec2 n = -m_polygonB.normals[i];
|
|
|
|
float32 s1 = b2Dot(n, m_polygonB.vertices[i] - m_v1);
|
|
float32 s2 = b2Dot(n, m_polygonB.vertices[i] - m_v2);
|
|
float32 s = b2Min(s1, s2);
|
|
|
|
if (s > m_radius)
|
|
{
|
|
// No collision
|
|
axis.type = b2EPAxis::e_edgeB;
|
|
axis.index = i;
|
|
axis.separation = s;
|
|
return axis;
|
|
}
|
|
|
|
// Adjacency
|
|
if (b2Dot(n, perp) >= 0.0f)
|
|
{
|
|
if (b2Dot(n - m_upperLimit, m_normal) < -b2_angularSlop)
|
|
{
|
|
continue;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
if (b2Dot(n - m_lowerLimit, m_normal) < -b2_angularSlop)
|
|
{
|
|
continue;
|
|
}
|
|
}
|
|
|
|
if (s > axis.separation)
|
|
{
|
|
axis.type = b2EPAxis::e_edgeB;
|
|
axis.index = i;
|
|
axis.separation = s;
|
|
}
|
|
}
|
|
|
|
return axis;
|
|
}
|
|
|
|
void b2CollideEdgeAndPolygon( b2Manifold* manifold,
|
|
const b2EdgeShape* edgeA, const b2Transform& xfA,
|
|
const b2PolygonShape* polygonB, const b2Transform& xfB)
|
|
{
|
|
b2EPCollider collider;
|
|
collider.Collide(manifold, edgeA, xfA, polygonB, xfB);
|
|
}
|