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fix issue with btMultiBody friction in combination with soft contacts (friction should not re-use normal contact cfm/erp)

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implement friction anchors, position friction correction, disabled by default. Use colObj->setCollisionFlag(flag | CF_HAS_FRICTION_ANCHOR); See test/RobotClientAPI/SlopeFrictionMain.cpp. In URDF or SDF, add <friction_anchor/> in <contact> section of <link> to enable.
PhysicsServer: properly restore old activation state after releasing picked object
btMultiBodyConstraintSolver: disable flip/flop of contact/friction constraint solving by default (it breaks some internal flaky unit tests)
This commit is contained in:
Erwin Coumans
2017-03-20 10:58:07 -07:00
parent 865d37fcb5
commit 0b017b0f53
18 changed files with 299 additions and 91 deletions
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13
src/BulletDynamics/ConstraintSolver/btContactSolverInfo.h
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@@ -43,10 +43,13 @@ struct btContactSolverInfoData
btScalar m_restitution;
int m_numIterations;
btScalar m_maxErrorReduction;
btScalar m_sor;
btScalar m_erp;//used as Baumgarte factor
btScalar m_erp2;//used in Split Impulse
btScalar m_globalCfm;//constraint force mixing
btScalar m_sor;//successive over-relaxation term
btScalar m_erp;//error reduction for non-contact constraints
btScalar m_erp2;//error reduction for contact constraints
btScalar m_globalCfm;//constraint force mixing for contacts and non-contacts
btScalar m_frictionERP;//error reduction for friction constraints
btScalar m_frictionCFM;//constraint force mixing for friction constraints
int m_splitImpulse;
btScalar m_splitImpulsePenetrationThreshold;
btScalar m_splitImpulseTurnErp;
@@ -79,6 +82,8 @@ struct btContactSolverInfo : public btContactSolverInfoData
m_erp = btScalar(0.2);
m_erp2 = btScalar(0.2);
m_globalCfm = btScalar(0.);
m_frictionERP = btScalar(0.2);//positional friction 'anchors' are disabled by default
m_frictionCFM = btScalar(0.);
m_sor = btScalar(1.);
m_splitImpulse = true;
m_splitImpulsePenetrationThreshold = -.04f;

34
src/BulletDynamics/ConstraintSolver/btSequentialImpulseConstraintSolver.cpp
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@@ -534,7 +534,7 @@ void btSequentialImpulseConstraintSolver::applyAnisotropicFriction(btCollisionOb
void btSequentialImpulseConstraintSolver::setupFrictionConstraint(btSolverConstraint& solverConstraint, const btVector3& normalAxis,int solverBodyIdA,int solverBodyIdB,btManifoldPoint& cp,const btVector3& rel_pos1,const btVector3& rel_pos2,btCollisionObject* colObj0,btCollisionObject* colObj1, btScalar relaxation, btScalar desiredVelocity, btScalar cfmSlip)
void btSequentialImpulseConstraintSolver::setupFrictionConstraint(btSolverConstraint& solverConstraint, const btVector3& normalAxis,int solverBodyIdA,int solverBodyIdB,btManifoldPoint& cp,const btVector3& rel_pos1,const btVector3& rel_pos2,btCollisionObject* colObj0,btCollisionObject* colObj1, btScalar relaxation, const btContactSolverInfo& infoGlobal, btScalar desiredVelocity, btScalar cfmSlip)
{
@@ -612,7 +612,17 @@ void btSequentialImpulseConstraintSolver::setupFrictionConstraint(btSolverConstr
btScalar velocityError = desiredVelocity - rel_vel;
btScalar velocityImpulse = velocityError * solverConstraint.m_jacDiagABInv;
solverConstraint.m_rhs = velocityImpulse;
btScalar penetrationImpulse = btScalar(0);
if (cp.m_contactPointFlags & BT_CONTACT_FLAG_FRICTION_ANCHOR)
{
btScalar distance = (cp.getPositionWorldOnA() - cp.getPositionWorldOnB()).dot(normalAxis);
btScalar positionalError = -distance * infoGlobal.m_frictionERP/infoGlobal.m_timeStep;
penetrationImpulse = positionalError*solverConstraint.m_jacDiagABInv;
}
solverConstraint.m_rhs = penetrationImpulse + velocityImpulse;
solverConstraint.m_rhsPenetration = 0.f;
solverConstraint.m_cfm = cfmSlip;
solverConstraint.m_lowerLimit = -solverConstraint.m_friction;
@@ -621,12 +631,12 @@ void btSequentialImpulseConstraintSolver::setupFrictionConstraint(btSolverConstr
}
}
btSolverConstraint& btSequentialImpulseConstraintSolver::addFrictionConstraint(const btVector3& normalAxis,int solverBodyIdA,int solverBodyIdB,int frictionIndex,btManifoldPoint& cp,const btVector3& rel_pos1,const btVector3& rel_pos2,btCollisionObject* colObj0,btCollisionObject* colObj1, btScalar relaxation, btScalar desiredVelocity, btScalar cfmSlip)
btSolverConstraint& btSequentialImpulseConstraintSolver::addFrictionConstraint(const btVector3& normalAxis,int solverBodyIdA,int solverBodyIdB,int frictionIndex,btManifoldPoint& cp,const btVector3& rel_pos1,const btVector3& rel_pos2,btCollisionObject* colObj0,btCollisionObject* colObj1, btScalar relaxation, const btContactSolverInfo& infoGlobal, btScalar desiredVelocity, btScalar cfmSlip)
{
btSolverConstraint& solverConstraint = m_tmpSolverContactFrictionConstraintPool.expandNonInitializing();
solverConstraint.m_frictionIndex = frictionIndex;
setupFrictionConstraint(solverConstraint, normalAxis, solverBodyIdA, solverBodyIdB, cp, rel_pos1, rel_pos2,
colObj0, colObj1, relaxation, desiredVelocity, cfmSlip);
colObj0, colObj1, relaxation, infoGlobal, desiredVelocity, cfmSlip);
return solverConstraint;
}
@@ -1168,6 +1178,7 @@ void btSequentialImpulseConstraintSolver::convertContact(btPersistentManifold* m
///In that case, you can set the target relative motion in each friction direction (cp.m_contactMotion1 and cp.m_contactMotion2)
///this will give a conveyor belt effect
///
if (!(infoGlobal.m_solverMode & SOLVER_ENABLE_FRICTION_DIRECTION_CACHING) || !(cp.m_contactPointFlags&BT_CONTACT_FLAG_LATERAL_FRICTION_INITIALIZED))
{
cp.m_lateralFrictionDir1 = vel - cp.m_normalWorldOnB * rel_vel;
@@ -1177,7 +1188,7 @@ void btSequentialImpulseConstraintSolver::convertContact(btPersistentManifold* m
cp.m_lateralFrictionDir1 *= 1.f/btSqrt(lat_rel_vel);
applyAnisotropicFriction(colObj0,cp.m_lateralFrictionDir1,btCollisionObject::CF_ANISOTROPIC_FRICTION);
applyAnisotropicFriction(colObj1,cp.m_lateralFrictionDir1,btCollisionObject::CF_ANISOTROPIC_FRICTION);
addFrictionConstraint(cp.m_lateralFrictionDir1,solverBodyIdA,solverBodyIdB,frictionIndex,cp,rel_pos1,rel_pos2,colObj0,colObj1, relaxation);
addFrictionConstraint(cp.m_lateralFrictionDir1,solverBodyIdA,solverBodyIdB,frictionIndex,cp,rel_pos1,rel_pos2,colObj0,colObj1, relaxation,infoGlobal);
if((infoGlobal.m_solverMode & SOLVER_USE_2_FRICTION_DIRECTIONS))
{
@@ -1185,7 +1196,7 @@ void btSequentialImpulseConstraintSolver::convertContact(btPersistentManifold* m
cp.m_lateralFrictionDir2.normalize();//??
applyAnisotropicFriction(colObj0,cp.m_lateralFrictionDir2,btCollisionObject::CF_ANISOTROPIC_FRICTION);
applyAnisotropicFriction(colObj1,cp.m_lateralFrictionDir2,btCollisionObject::CF_ANISOTROPIC_FRICTION);
addFrictionConstraint(cp.m_lateralFrictionDir2,solverBodyIdA,solverBodyIdB,frictionIndex,cp,rel_pos1,rel_pos2,colObj0,colObj1, relaxation);
addFrictionConstraint(cp.m_lateralFrictionDir2,solverBodyIdA,solverBodyIdB,frictionIndex,cp,rel_pos1,rel_pos2,colObj0,colObj1, relaxation, infoGlobal);
}
} else
@@ -1194,13 +1205,13 @@ void btSequentialImpulseConstraintSolver::convertContact(btPersistentManifold* m
applyAnisotropicFriction(colObj0,cp.m_lateralFrictionDir1,btCollisionObject::CF_ANISOTROPIC_FRICTION);
applyAnisotropicFriction(colObj1,cp.m_lateralFrictionDir1,btCollisionObject::CF_ANISOTROPIC_FRICTION);
addFrictionConstraint(cp.m_lateralFrictionDir1,solverBodyIdA,solverBodyIdB,frictionIndex,cp,rel_pos1,rel_pos2,colObj0,colObj1, relaxation);
addFrictionConstraint(cp.m_lateralFrictionDir1,solverBodyIdA,solverBodyIdB,frictionIndex,cp,rel_pos1,rel_pos2,colObj0,colObj1, relaxation, infoGlobal);
if ((infoGlobal.m_solverMode & SOLVER_USE_2_FRICTION_DIRECTIONS))
{
applyAnisotropicFriction(colObj0,cp.m_lateralFrictionDir2,btCollisionObject::CF_ANISOTROPIC_FRICTION);
applyAnisotropicFriction(colObj1,cp.m_lateralFrictionDir2,btCollisionObject::CF_ANISOTROPIC_FRICTION);
addFrictionConstraint(cp.m_lateralFrictionDir2,solverBodyIdA,solverBodyIdB,frictionIndex,cp,rel_pos1,rel_pos2,colObj0,colObj1, relaxation);
addFrictionConstraint(cp.m_lateralFrictionDir2,solverBodyIdA,solverBodyIdB,frictionIndex,cp,rel_pos1,rel_pos2,colObj0,colObj1, relaxation, infoGlobal);
}
@@ -1212,10 +1223,10 @@ void btSequentialImpulseConstraintSolver::convertContact(btPersistentManifold* m
} else
{
addFrictionConstraint(cp.m_lateralFrictionDir1,solverBodyIdA,solverBodyIdB,frictionIndex,cp,rel_pos1,rel_pos2,colObj0,colObj1, relaxation,cp.m_contactMotion1, cp.m_frictionCFM);
addFrictionConstraint(cp.m_lateralFrictionDir1,solverBodyIdA,solverBodyIdB,frictionIndex,cp,rel_pos1,rel_pos2,colObj0,colObj1, relaxation, infoGlobal, cp.m_contactMotion1, cp.m_frictionCFM);
if ((infoGlobal.m_solverMode & SOLVER_USE_2_FRICTION_DIRECTIONS))
addFrictionConstraint(cp.m_lateralFrictionDir2,solverBodyIdA,solverBodyIdB,frictionIndex,cp,rel_pos1,rel_pos2,colObj0,colObj1, relaxation, cp.m_contactMotion2, cp.m_frictionCFM);
addFrictionConstraint(cp.m_lateralFrictionDir2,solverBodyIdA,solverBodyIdB,frictionIndex,cp,rel_pos1,rel_pos2,colObj0,colObj1, relaxation, infoGlobal, cp.m_contactMotion2, cp.m_frictionCFM);
}
setFrictionConstraintImpulse( solverConstraint, solverBodyIdA, solverBodyIdB, cp, infoGlobal);
@@ -1526,7 +1537,8 @@ btScalar btSequentialImpulseConstraintSolver::solveGroupCacheFriendlySetup(btCol
sum += iMJaB.dot(solverConstraint.m_relpos2CrossNormal);
btScalar fsum = btFabs(sum);
btAssert(fsum > SIMD_EPSILON);
solverConstraint.m_jacDiagABInv = fsum>SIMD_EPSILON?btScalar(1.)/sum : 0.f;
btScalar sorRelaxation = 1.f;//todo: get from globalInfo?
solverConstraint.m_jacDiagABInv = fsum>SIMD_EPSILON?sorRelaxation/sum : 0.f;
}

3
src/BulletDynamics/ConstraintSolver/btSequentialImpulseConstraintSolver.h
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@@ -62,6 +62,7 @@ protected:
void setupFrictionConstraint( btSolverConstraint& solverConstraint, const btVector3& normalAxis,int solverBodyIdA,int solverBodyIdB,
btManifoldPoint& cp,const btVector3& rel_pos1,const btVector3& rel_pos2,
btCollisionObject* colObj0,btCollisionObject* colObj1, btScalar relaxation,
const btContactSolverInfo& infoGlobal,
btScalar desiredVelocity=0., btScalar cfmSlip=0.);
void setupTorsionalFrictionConstraint( btSolverConstraint& solverConstraint, const btVector3& normalAxis,int solverBodyIdA,int solverBodyIdB,
@@ -69,7 +70,7 @@ protected:
btCollisionObject* colObj0,btCollisionObject* colObj1, btScalar relaxation,
btScalar desiredVelocity=0., btScalar cfmSlip=0.);
btSolverConstraint& addFrictionConstraint(const btVector3& normalAxis,int solverBodyIdA,int solverBodyIdB,int frictionIndex,btManifoldPoint& cp,const btVector3& rel_pos1,const btVector3& rel_pos2,btCollisionObject* colObj0,btCollisionObject* colObj1, btScalar relaxation, btScalar desiredVelocity=0., btScalar cfmSlip=0.);
btSolverConstraint& addFrictionConstraint(const btVector3& normalAxis,int solverBodyIdA,int solverBodyIdB,int frictionIndex,btManifoldPoint& cp,const btVector3& rel_pos1,const btVector3& rel_pos2,btCollisionObject* colObj0,btCollisionObject* colObj1, btScalar relaxation, const btContactSolverInfo& infoGlobal, btScalar desiredVelocity=0., btScalar cfmSlip=0.);
btSolverConstraint& addTorsionalFrictionConstraint(const btVector3& normalAxis,int solverBodyIdA,int solverBodyIdB,int frictionIndex,btManifoldPoint& cp,btScalar torsionalFriction, const btVector3& rel_pos1,const btVector3& rel_pos2,btCollisionObject* colObj0,btCollisionObject* colObj1, btScalar relaxation, btScalar desiredVelocity=0, btScalar cfmSlip=0.f);

98
src/BulletDynamics/Featherstone/btMultiBodyConstraintSolver.cpp
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@@ -50,7 +50,7 @@ btScalar btMultiBodyConstraintSolver::solveSingleIteration(int iteration, btColl
//solve featherstone normal contact
for (int j0=0;j0<m_multiBodyNormalContactConstraints.size();j0++)
{
int index = iteration&1? j0 : m_multiBodyNormalContactConstraints.size()-1-j0;
int index = j0;//iteration&1? j0 : m_multiBodyNormalContactConstraints.size()-1-j0;
btMultiBodySolverConstraint& constraint = m_multiBodyNormalContactConstraints[index];
btScalar residual = 0.f;
@@ -74,7 +74,7 @@ btScalar btMultiBodyConstraintSolver::solveSingleIteration(int iteration, btColl
{
if (iteration < infoGlobal.m_numIterations)
{
int index = iteration&1? j1 : m_multiBodyFrictionContactConstraints.size()-1-j1;
int index = j1;//iteration&1? j1 : m_multiBodyFrictionContactConstraints.size()-1-j1;
btMultiBodySolverConstraint& frictionConstraint = m_multiBodyFrictionContactConstraints[index];
btScalar totalImpulse = m_multiBodyNormalContactConstraints[frictionConstraint.m_frictionIndex].m_appliedImpulse;
@@ -244,32 +244,39 @@ void btMultiBodyConstraintSolver::setupMultiBodyContactConstraint(btMultiBodySol
//cfm = 1 / ( dt * kp + kd )
//erp = dt * kp / ( dt * kp + kd )
btScalar cfm = infoGlobal.m_globalCfm;
btScalar erp = infoGlobal.m_erp2;
if ((cp.m_contactPointFlags&BT_CONTACT_FLAG_HAS_CONTACT_CFM) || (cp.m_contactPointFlags&BT_CONTACT_FLAG_HAS_CONTACT_ERP))
{
if (cp.m_contactPointFlags&BT_CONTACT_FLAG_HAS_CONTACT_CFM)
cfm = cp.m_contactCFM;
if (cp.m_contactPointFlags&BT_CONTACT_FLAG_HAS_CONTACT_ERP)
erp = cp.m_contactERP;
} else
{
if (cp.m_contactPointFlags & BT_CONTACT_FLAG_CONTACT_STIFFNESS_DAMPING)
{
btScalar denom = ( infoGlobal.m_timeStep * cp.m_combinedContactStiffness1 + cp.m_combinedContactDamping1 );
if (denom < SIMD_EPSILON)
{
denom = SIMD_EPSILON;
}
cfm = btScalar(1) / denom;
erp = (infoGlobal.m_timeStep * cp.m_combinedContactStiffness1) / denom;
}
}
cfm *= invTimeStep;
btScalar cfm;
btScalar erp;
if (isFriction)
{
cfm = infoGlobal.m_frictionCFM;
erp = infoGlobal.m_frictionERP;
} else
{
cfm = infoGlobal.m_globalCfm;
erp = infoGlobal.m_erp2;
if ((cp.m_contactPointFlags&BT_CONTACT_FLAG_HAS_CONTACT_CFM) || (cp.m_contactPointFlags&BT_CONTACT_FLAG_HAS_CONTACT_ERP))
{
if (cp.m_contactPointFlags&BT_CONTACT_FLAG_HAS_CONTACT_CFM)
cfm = cp.m_contactCFM;
if (cp.m_contactPointFlags&BT_CONTACT_FLAG_HAS_CONTACT_ERP)
erp = cp.m_contactERP;
} else
{
if (cp.m_contactPointFlags & BT_CONTACT_FLAG_CONTACT_STIFFNESS_DAMPING)
{
btScalar denom = ( infoGlobal.m_timeStep * cp.m_combinedContactStiffness1 + cp.m_combinedContactDamping1 );
if (denom < SIMD_EPSILON)
{
denom = SIMD_EPSILON;
}
cfm = btScalar(1) / denom;
erp = (infoGlobal.m_timeStep * cp.m_combinedContactStiffness1) / denom;
}
}
}
cfm *= invTimeStep;
if (multiBodyA)
{
@@ -429,8 +436,16 @@ void btMultiBodyConstraintSolver::setupMultiBodyContactConstraint(btMultiBodySol
btScalar restitution = 0.f;
btScalar penetration = isFriction? 0 : cp.getDistance()+infoGlobal.m_linearSlop;
btScalar distance = 0;
if (!isFriction)
{
distance = cp.getDistance()+infoGlobal.m_linearSlop;
} else
{
distance = (cp.getPositionWorldOnA() - cp.getPositionWorldOnB()).dot(contactNormal);
}
btScalar rel_vel = 0.f;
int ndofA = 0;
int ndofB = 0;
@@ -526,14 +541,17 @@ void btMultiBodyConstraintSolver::setupMultiBodyContactConstraint(btMultiBodySol
btScalar positionalError = 0.f;
btScalar velocityError = restitution - rel_vel;// * damping; //note for friction restitution is always set to 0 (check above) so it is acutally velocityError = -rel_vel for friction
if (penetration>0)
if (distance>0 && !isFriction)
{
positionalError = 0;
velocityError -= penetration / infoGlobal.m_timeStep;
velocityError -= distance / infoGlobal.m_timeStep;
} else
{
positionalError = -penetration * erp/infoGlobal.m_timeStep;
if (cp.m_contactPointFlags & BT_CONTACT_FLAG_FRICTION_ANCHOR)
{
positionalError = -distance * erp/infoGlobal.m_timeStep;
}
}
btScalar penetrationImpulse = positionalError*solverConstraint.m_jacDiagABInv;
@@ -560,7 +578,7 @@ void btMultiBodyConstraintSolver::setupMultiBodyContactConstraint(btMultiBodySol
}
else
{
solverConstraint.m_rhs = velocityImpulse;
solverConstraint.m_rhs = penetrationImpulse+velocityImpulse;
solverConstraint.m_rhsPenetration = 0.f;
solverConstraint.m_lowerLimit = -solverConstraint.m_friction;
solverConstraint.m_upperLimit = solverConstraint.m_friction;
@@ -1028,12 +1046,18 @@ void btMultiBodyConstraintSolver::convertMultiBodyContact(btPersistentManifold*
applyAnisotropicFriction(colObj1,cp.m_lateralFrictionDir1,btCollisionObject::CF_ANISOTROPIC_FRICTION);
addMultiBodyFrictionConstraint(cp.m_lateralFrictionDir1,manifold,frictionIndex,cp,colObj0,colObj1, relaxation,infoGlobal);
if (rollingFriction > 0)
if (rollingFriction > 0 )
{
addMultiBodyTorsionalFrictionConstraint(cp.m_normalWorldOnB,manifold,frictionIndex,cp,cp.m_combinedSpinningFriction, colObj0,colObj1, relaxation,infoGlobal);
addMultiBodyTorsionalFrictionConstraint(cp.m_lateralFrictionDir1,manifold,frictionIndex,cp,cp.m_combinedRollingFriction, colObj0,colObj1, relaxation,infoGlobal);
addMultiBodyTorsionalFrictionConstraint(cp.m_lateralFrictionDir2,manifold,frictionIndex,cp,cp.m_combinedRollingFriction, colObj0,colObj1, relaxation,infoGlobal);
if (cp.m_combinedSpinningFriction>0)
{
addMultiBodyTorsionalFrictionConstraint(cp.m_normalWorldOnB,manifold,frictionIndex,cp,cp.m_combinedSpinningFriction, colObj0,colObj1, relaxation,infoGlobal);
}
if (cp.m_combinedRollingFriction>0)
{
addMultiBodyTorsionalFrictionConstraint(cp.m_lateralFrictionDir1,manifold,frictionIndex,cp,cp.m_combinedRollingFriction, colObj0,colObj1, relaxation,infoGlobal);
addMultiBodyTorsionalFrictionConstraint(cp.m_lateralFrictionDir2,manifold,frictionIndex,cp,cp.m_combinedRollingFriction, colObj0,colObj1, relaxation,infoGlobal);
}
rollingFriction--;
}