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Simplify GJK. Still needs double precision for large differences of feature scales.

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Extract faces directly from btConvexHullComputer (in initializePolyhedralFeatures), instead of reconstructing them, thanks to Josh Klint in #1654
PyBullet: use initializePolyhedralFeatures for convex hulls and boxes (to allow SAT)
PyBullet: expose setPhysicsEngineParameter(enableSAT=0 or 1) to enable Separating Axis Test based collision detection for convex vs convex/box and convex versus concave triangles (in a triangle mesh).
This commit is contained in:
erwincoumans
2018-06-12 16:08:46 -07:00
parent a342af0382
commit 97c6937388
13 changed files with 257 additions and 211 deletions
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146
src/BulletCollision/CollisionDispatch/btConvexConvexAlgorithm.cpp
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@@ -28,6 +28,7 @@ subject to the following restrictions:
#include "BulletCollision/CollisionShapes/btConvexShape.h"
#include "BulletCollision/CollisionShapes/btCapsuleShape.h"
#include "BulletCollision/CollisionShapes/btTriangleShape.h"
#include "BulletCollision/CollisionShapes/btConvexPolyhedron.h"
@@ -442,10 +443,26 @@ void btConvexConvexAlgorithm ::processCollision (const btCollisionObjectWrapper*
struct btDummyResult : public btDiscreteCollisionDetectorInterface::Result
{
btVector3 m_normalOnBInWorld;
btVector3 m_pointInWorld;
btScalar m_depth;
bool m_hasContact;
btDummyResult()
: m_hasContact(false)
{
}
virtual void setShapeIdentifiersA(int partId0,int index0){}
virtual void setShapeIdentifiersB(int partId1,int index1){}
virtual void addContactPoint(const btVector3& normalOnBInWorld,const btVector3& pointInWorld,btScalar depth)
{
m_hasContact = true;
m_normalOnBInWorld = normalOnBInWorld;
m_pointInWorld = pointInWorld;
m_depth = depth;
}
};
@@ -560,15 +577,18 @@ void btConvexConvexAlgorithm ::processCollision (const btCollisionObjectWrapper*
} else
{
//we can also deal with convex versus triangle (without connectivity data)
if (polyhedronA->getConvexPolyhedron() && polyhedronB->getShapeType()==TRIANGLE_SHAPE_PROXYTYPE)
if (dispatchInfo.m_enableSatConvex && polyhedronA->getConvexPolyhedron() && polyhedronB->getShapeType()==TRIANGLE_SHAPE_PROXYTYPE)
{
btVertexArray vertices;
btVertexArray worldSpaceVertices;
btTriangleShape* tri = (btTriangleShape*)polyhedronB;
vertices.push_back( body1Wrap->getWorldTransform()*tri->m_vertices1[0]);
vertices.push_back( body1Wrap->getWorldTransform()*tri->m_vertices1[1]);
vertices.push_back( body1Wrap->getWorldTransform()*tri->m_vertices1[2]);
worldSpaceVertices.push_back( body1Wrap->getWorldTransform()*tri->m_vertices1[0]);
worldSpaceVertices.push_back( body1Wrap->getWorldTransform()*tri->m_vertices1[1]);
worldSpaceVertices.push_back( body1Wrap->getWorldTransform()*tri->m_vertices1[2]);
//tri->initializePolyhedralFeatures();
@@ -579,17 +599,97 @@ void btConvexConvexAlgorithm ::processCollision (const btCollisionObjectWrapper*
btScalar maxDist = threshold;
bool foundSepAxis = false;
if (0)
bool useSatSepNormal = true;
if (useSatSepNormal)
{
polyhedronB->initializePolyhedralFeatures();
if (0)
{
//initializePolyhedralFeatures performs a convex hull computation, not needed for a single triangle
polyhedronB->initializePolyhedralFeatures();
} else
{
btVector3 uniqueEdges[3] = {tri->m_vertices1[1]-tri->m_vertices1[0],
tri->m_vertices1[2]-tri->m_vertices1[1],
tri->m_vertices1[0]-tri->m_vertices1[2]};
uniqueEdges[0].normalize();
uniqueEdges[1].normalize();
uniqueEdges[2].normalize();
btConvexPolyhedron polyhedron;
polyhedron.m_vertices.push_back(tri->m_vertices1[2]);
polyhedron.m_vertices.push_back(tri->m_vertices1[0]);
polyhedron.m_vertices.push_back(tri->m_vertices1[1]);
{
btFace combinedFaceA;
combinedFaceA.m_indices.push_back(0);
combinedFaceA.m_indices.push_back(1);
combinedFaceA.m_indices.push_back(2);
btVector3 faceNormal = uniqueEdges[0].cross(uniqueEdges[1]);
faceNormal.normalize();
btScalar planeEq=1e30f;
for (int v=0;v<combinedFaceA.m_indices.size();v++)
{
btScalar eq = tri->m_vertices1[combinedFaceA.m_indices[v]].dot(faceNormal);
if (planeEq>eq)
{
planeEq=eq;
}
}
combinedFaceA.m_plane[0] = faceNormal[0];
combinedFaceA.m_plane[1] = faceNormal[1];
combinedFaceA.m_plane[2] = faceNormal[2];
combinedFaceA.m_plane[3] = -planeEq;
polyhedron.m_faces.push_back(combinedFaceA);
}
{
btFace combinedFaceB;
combinedFaceB.m_indices.push_back(0);
combinedFaceB.m_indices.push_back(2);
combinedFaceB.m_indices.push_back(1);
btVector3 faceNormal = -uniqueEdges[0].cross(uniqueEdges[1]);
faceNormal.normalize();
btScalar planeEq=1e30f;
for (int v=0;v<combinedFaceB.m_indices.size();v++)
{
btScalar eq = tri->m_vertices1[combinedFaceB.m_indices[v]].dot(faceNormal);
if (planeEq>eq)
{
planeEq=eq;
}
}
combinedFaceB.m_plane[0] = faceNormal[0];
combinedFaceB.m_plane[1] = faceNormal[1];
combinedFaceB.m_plane[2] = faceNormal[2];
combinedFaceB.m_plane[3] = -planeEq;
polyhedron.m_faces.push_back(combinedFaceB);
}
polyhedron.m_uniqueEdges.push_back(uniqueEdges[0]);
polyhedron.m_uniqueEdges.push_back(uniqueEdges[1]);
polyhedron.m_uniqueEdges.push_back(uniqueEdges[2]);
polyhedron.initialize2();
polyhedronB->setPolyhedralFeatures(polyhedron);
}
foundSepAxis = btPolyhedralContactClipping::findSeparatingAxis(
*polyhedronA->getConvexPolyhedron(), *polyhedronB->getConvexPolyhedron(),
body0Wrap->getWorldTransform(),
body1Wrap->getWorldTransform(),
sepNormalWorldSpace,*resultOut);
*polyhedronA->getConvexPolyhedron(), *polyhedronB->getConvexPolyhedron(),
body0Wrap->getWorldTransform(),
body1Wrap->getWorldTransform(),
sepNormalWorldSpace,*resultOut);
// printf("sepNormalWorldSpace=%f,%f,%f\n",sepNormalWorldSpace.getX(),sepNormalWorldSpace.getY(),sepNormalWorldSpace.getZ());
} else
}
else
{
#ifdef ZERO_MARGIN
gjkPairDetector.setIgnoreMargin(true);
@@ -598,6 +698,24 @@ void btConvexConvexAlgorithm ::processCollision (const btCollisionObjectWrapper*
gjkPairDetector.getClosestPoints(input,dummy,dispatchInfo.m_debugDraw);
#endif//ZERO_MARGIN
if (dummy.m_hasContact && dummy.m_depth<0)
{
if (foundSepAxis)
{
if (dummy.m_normalOnBInWorld.dot(sepNormalWorldSpace)<0.99)
{
printf("?\n");
}
} else
{
printf("!\n");
}
sepNormalWorldSpace.setValue(0,0,1);// = dummy.m_normalOnBInWorld;
//minDist = dummy.m_depth;
foundSepAxis = true;
}
#if 0
btScalar l2 = gjkPairDetector.getCachedSeparatingAxis().length2();
if (l2>SIMD_EPSILON)
{
@@ -607,6 +725,7 @@ void btConvexConvexAlgorithm ::processCollision (const btCollisionObjectWrapper*
minDist = gjkPairDetector.getCachedSeparatingDistance()-min0->getMargin()-min1->getMargin();
foundSepAxis = true;
}
#endif
}
@@ -614,7 +733,7 @@ void btConvexConvexAlgorithm ::processCollision (const btCollisionObjectWrapper*
{
worldVertsB2.resize(0);
btPolyhedralContactClipping::clipFaceAgainstHull(sepNormalWorldSpace, *polyhedronA->getConvexPolyhedron(),
body0Wrap->getWorldTransform(), vertices, worldVertsB2,minDist-threshold, maxDist, *resultOut);
body0Wrap->getWorldTransform(), worldSpaceVertices, worldVertsB2,minDist-threshold, maxDist, *resultOut);
}
@@ -625,6 +744,7 @@ void btConvexConvexAlgorithm ::processCollision (const btCollisionObjectWrapper*
return;
}
}

12
src/BulletCollision/CollisionShapes/btConvexPolyhedron.cpp
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@@ -104,9 +104,9 @@ void btConvexPolyhedron::initialize()
btHashMap<btInternalVertexPair,btInternalEdge> edges;
btScalar TotalArea = 0.0f;
m_localCenter.setValue(0, 0, 0);
for(int i=0;i<m_faces.size();i++)
{
int numVertices = m_faces[i].m_indices.size();
@@ -172,6 +172,13 @@ void btConvexPolyhedron::initialize()
}
#endif//USE_CONNECTED_FACES
initialize2();
}
void btConvexPolyhedron::initialize2()
{
m_localCenter.setValue(0, 0, 0);
btScalar TotalArea = 0.0f;
for(int i=0;i<m_faces.size();i++)
{
int numVertices = m_faces[i].m_indices.size();
@@ -274,7 +281,6 @@ void btConvexPolyhedron::initialize()
}
#endif
}
void btConvexPolyhedron::project(const btTransform& trans, const btVector3& dir, btScalar& minProj, btScalar& maxProj, btVector3& witnesPtMin,btVector3& witnesPtMax) const
{
minProj = FLT_MAX;

1
src/BulletCollision/CollisionShapes/btConvexPolyhedron.h
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@@ -54,6 +54,7 @@ ATTRIBUTE_ALIGNED16(class) btConvexPolyhedron
btVector3 mE;
void initialize();
void initialize2();
bool testContainment() const;
void project(const btTransform& trans, const btVector3& dir, btScalar& minProj, btScalar& maxProj, btVector3& witnesPtMin,btVector3& witnesPtMax) const;

79
src/BulletCollision/CollisionShapes/btPolyhedralConvexShape.cpp
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@@ -39,6 +39,17 @@ btPolyhedralConvexShape::~btPolyhedralConvexShape()
}
}
void btPolyhedralConvexShape::setPolyhedralFeatures(btConvexPolyhedron& polyhedron)
{
if (m_polyhedron)
{
*m_polyhedron = polyhedron;
} else
{
void* mem = btAlignedAlloc(sizeof(btConvexPolyhedron),16);
m_polyhedron = new (mem) btConvexPolyhedron(polyhedron);
}
}
bool btPolyhedralConvexShape::initializePolyhedralFeatures(int shiftVerticesByMargin)
{
@@ -87,7 +98,71 @@ bool btPolyhedralConvexShape::initializePolyhedralFeatures(int shiftVerticesByMa
conv.compute(&orgVertices[0].getX(), sizeof(btVector3),orgVertices.size(),0.f,0.f);
}
#ifndef BT_RECONSTRUCT_FACES
int numVertices = conv.vertices.size();
m_polyhedron->m_vertices.resize(numVertices);
for (int p=0;p<numVertices;p++)
{
m_polyhedron->m_vertices[p] = conv.vertices[p];
}
int v0, v1;
for (int j = 0; j < conv.faces.size(); j++)
{
btVector3 edges[3];
int numEdges = 0;
btFace combinedFace;
const btConvexHullComputer::Edge* edge = &conv.edges[conv.faces[j]];
v0 = edge->getSourceVertex();
int prevVertex=v0;
combinedFace.m_indices.push_back(v0);
v1 = edge->getTargetVertex();
while (v1 != v0)
{
btVector3 wa = conv.vertices[prevVertex];
btVector3 wb = conv.vertices[v1];
btVector3 newEdge = wb-wa;
newEdge.normalize();
if (numEdges<2)
edges[numEdges++] = newEdge;
//face->addIndex(v1);
combinedFace.m_indices.push_back(v1);
edge = edge->getNextEdgeOfFace();
prevVertex = v1;
int v01 = edge->getSourceVertex();
v1 = edge->getTargetVertex();
}
btAssert(combinedFace.m_indices.size() > 2);
btVector3 faceNormal = edges[0].cross(edges[1]);
faceNormal.normalize();
btScalar planeEq=1e30f;
for (int v=0;v<combinedFace.m_indices.size();v++)
{
btScalar eq = m_polyhedron->m_vertices[combinedFace.m_indices[v]].dot(faceNormal);
if (planeEq>eq)
{
planeEq=eq;
}
}
combinedFace.m_plane[0] = faceNormal.getX();
combinedFace.m_plane[1] = faceNormal.getY();
combinedFace.m_plane[2] = faceNormal.getZ();
combinedFace.m_plane[3] = -planeEq;
m_polyhedron->m_faces.push_back(combinedFace);
}
#else//BT_RECONSTRUCT_FACES
btAlignedObjectArray<btVector3> faceNormals;
int numFaces = conv.faces.size();
@@ -311,7 +386,9 @@ bool btPolyhedralConvexShape::initializePolyhedralFeatures(int shiftVerticesByMa
}
#endif //BT_RECONSTRUCT_FACES
m_polyhedron->initialize();
return true;

3
src/BulletCollision/CollisionShapes/btPolyhedralConvexShape.h
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@@ -43,6 +43,9 @@ public:
///experimental/work-in-progress
virtual bool initializePolyhedralFeatures(int shiftVerticesByMargin=0);
virtual void setPolyhedralFeatures(btConvexPolyhedron& polyhedron);
const btConvexPolyhedron* getConvexPolyhedron() const
{
return m_polyhedron;

188
src/BulletCollision/NarrowPhaseCollision/btGjkPairDetector.cpp
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@@ -19,7 +19,6 @@ subject to the following restrictions:
#include "BulletCollision/NarrowPhaseCollision/btConvexPenetrationDepthSolver.h"
#if defined(DEBUG) || defined (_DEBUG)
//#define TEST_NON_VIRTUAL 1
#include <stdio.h> //for debug printf
@@ -29,14 +28,6 @@ subject to the following restrictions:
#endif //__SPU__
#endif
//must be above the machine epsilon
#ifdef BT_USE_DOUBLE_PRECISION
#define REL_ERROR2 btScalar(1.0e-12)
btScalar gGjkEpaPenetrationTolerance = 1.0e-12;
#else
#define REL_ERROR2 btScalar(1.0e-6)
btScalar gGjkEpaPenetrationTolerance = 0.001;
#endif
//temp globals, to improve GJK/EPA/penetration calculations
int gNumDeepPenetrationChecks = 0;
@@ -136,177 +127,7 @@ void btGjkPairDetector::getClosestPointsNonVirtual(const ClosestPointInput& inpu
m_simplexSolver->reset();
for ( ; ; )
//while (true)
{
btVector3 seperatingAxisInA = (-m_cachedSeparatingAxis)* input.m_transformA.getBasis();
btVector3 seperatingAxisInB = m_cachedSeparatingAxis* input.m_transformB.getBasis();
btVector3 pInA = m_minkowskiA->localGetSupportVertexWithoutMarginNonVirtual(seperatingAxisInA);
btVector3 qInB = m_minkowskiB->localGetSupportVertexWithoutMarginNonVirtual(seperatingAxisInB);
btVector3 pWorld = localTransA(pInA);
btVector3 qWorld = localTransB(qInB);
if (check2d)
{
pWorld[2] = 0.f;
qWorld[2] = 0.f;
}
btVector3 w = pWorld - qWorld;
delta = m_cachedSeparatingAxis.dot(w);
// potential exit, they don't overlap
if ((delta > btScalar(0.0)) && (delta * delta > squaredDistance * input.m_maximumDistanceSquared))
{
m_degenerateSimplex = 10;
checkSimplex=true;
//checkPenetration = false;
break;
}
//exit 0: the new point is already in the simplex, or we didn't come any closer
if (m_simplexSolver->inSimplex(w))
{
m_degenerateSimplex = 1;
checkSimplex = true;
break;
}
// are we getting any closer ?
btScalar f0 = squaredDistance - delta;
btScalar f1 = squaredDistance * REL_ERROR2;
if (f0 <= f1)
{
if (f0 <= btScalar(0.))
{
m_degenerateSimplex = 2;
} else
{
m_degenerateSimplex = 11;
}
checkSimplex = true;
break;
}
//add current vertex to simplex
m_simplexSolver->addVertex(w, pWorld, qWorld);
btVector3 newCachedSeparatingAxis;
//calculate the closest point to the origin (update vector v)
if (!m_simplexSolver->closest(newCachedSeparatingAxis))
{
m_degenerateSimplex = 3;
checkSimplex = true;
break;
}
if(newCachedSeparatingAxis.length2()<REL_ERROR2)
{
m_cachedSeparatingAxis = newCachedSeparatingAxis;
m_degenerateSimplex = 6;
checkSimplex = true;
break;
}
btScalar previousSquaredDistance = squaredDistance;
squaredDistance = newCachedSeparatingAxis.length2();
#if 0
///warning: this termination condition leads to some problems in 2d test case see Bullet/Demos/Box2dDemo
if (squaredDistance>previousSquaredDistance)
{
m_degenerateSimplex = 7;
squaredDistance = previousSquaredDistance;
checkSimplex = false;
break;
}
#endif //
//redundant m_simplexSolver->compute_points(pointOnA, pointOnB);
//are we getting any closer ?
if (previousSquaredDistance - squaredDistance <= SIMD_EPSILON * previousSquaredDistance)
{
// m_simplexSolver->backup_closest(m_cachedSeparatingAxis);
checkSimplex = true;
m_degenerateSimplex = 12;
break;
}
m_cachedSeparatingAxis = newCachedSeparatingAxis;
//degeneracy, this is typically due to invalid/uninitialized worldtransforms for a btCollisionObject
if (m_curIter++ > gGjkMaxIter)
{
#if defined(DEBUG) || defined (_DEBUG)
printf("btGjkPairDetector maxIter exceeded:%i\n",m_curIter);
printf("sepAxis=(%f,%f,%f), squaredDistance = %f, shapeTypeA=%i,shapeTypeB=%i\n",
m_cachedSeparatingAxis.getX(),
m_cachedSeparatingAxis.getY(),
m_cachedSeparatingAxis.getZ(),
squaredDistance,
m_minkowskiA->getShapeType(),
m_minkowskiB->getShapeType());
#endif
break;
}
bool check = (!m_simplexSolver->fullSimplex());
//bool check = (!m_simplexSolver->fullSimplex() && squaredDistance > SIMD_EPSILON * m_simplexSolver->maxVertex());
if (!check)
{
//do we need this backup_closest here ?
// m_simplexSolver->backup_closest(m_cachedSeparatingAxis);
m_degenerateSimplex = 13;
break;
}
}
if (checkSimplex)
{
m_simplexSolver->compute_points(pointOnA, pointOnB);
normalInB = m_cachedSeparatingAxis;
btScalar lenSqr =m_cachedSeparatingAxis.length2();
//valid normal
if (lenSqr < REL_ERROR2)
{
m_degenerateSimplex = 5;
}
if (lenSqr > SIMD_EPSILON*SIMD_EPSILON)
{
btScalar rlen = btScalar(1.) / btSqrt(lenSqr );
normalInB *= rlen; //normalize
btScalar s = btSqrt(squaredDistance);
btAssert(s > btScalar(0.0));
pointOnA -= m_cachedSeparatingAxis * (marginA / s);
pointOnB += m_cachedSeparatingAxis * (marginB / s);
distance = ((btScalar(1.)/rlen) - margin);
isValid = true;
m_lastUsedMethod = 1;
} else
{
m_lastUsedMethod = 2;
}
}
bool catchDegeneratePenetrationCase =
(m_catchDegeneracies && m_penetrationDepthSolver && m_degenerateSimplex && ((distance+margin) < gGjkEpaPenetrationTolerance));
bool catchDegeneratePenetrationCase = 1;
//if (checkPenetration && !isValid)
if (checkPenetration && (!isValid || catchDegeneratePenetrationCase ))
@@ -451,14 +272,9 @@ void btGjkPairDetector::getClosestPointsNonVirtual(const ClosestPointInput& inpu
}
}
output.addContactPoint(
normalInB,
pointOnB+positionOffset,
distance);
output.addContactPoint( normalInB, pointOnB+positionOffset, distance);
}
}