Bart/bullet3
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

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

Browse Source 
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
Download Patch File Download Diff File Expand all files Collapse all files

98
src/BulletDynamics/Featherstone/btMultiBodyConstraintSolver.cpp
View File

@@ -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--;
}