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support split impulse for deformable vs. rigid contact

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This commit is contained in:
Xuchen Han
2020-04-22 15:18:29 -07:00
parent e92d013730
commit 95287e458c
11 changed files with 121 additions and 44 deletions
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2
examples/DeformableDemo/SplitImpulse.cpp
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@@ -165,7 +165,7 @@ void SplitImpulse::initPhysics()
psb->setTotalMass(1);
psb->m_cfg.kKHR = 1; // collision hardness with kinematic objects
psb->m_cfg.kCHR = 1; // collision hardness with rigid body
psb->m_cfg.kDF = 0.1;
psb->m_cfg.kDF = 1;
psb->m_cfg.collisions = btSoftBody::fCollision::SDF_RD;
psb->m_cfg.collisions |= btSoftBody::fCollision::SDF_RDF;
getDeformableDynamicsWorld()->addSoftBody(psb);

10
src/BulletSoftBody/btDeformableBodySolver.cpp
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@@ -262,11 +262,6 @@ btScalar btDeformableBodySolver::solveContactConstraints(btCollisionObject** def
return maxSquaredResidual;
}
void btDeformableBodySolver::splitImpulseSetup(const btContactSolverInfo& infoGlobal)
{
m_objective->m_projection.splitImpulseSetup(infoGlobal);
}
void btDeformableBodySolver::updateVelocity()
{
int counter = 0;
@@ -286,7 +281,7 @@ void btDeformableBodySolver::updateVelocity()
{
m_dv[counter].setZero();
}
psb->m_nodes[j].m_v = m_backupVelocity[counter]+m_dv[counter];
psb->m_nodes[j].m_v = m_backupVelocity[counter] + m_dv[counter] - psb->m_nodes[j].m_splitv;
psb->m_maxSpeedSquared = btMax(psb->m_maxSpeedSquared, psb->m_nodes[j].m_v.length2());
++counter;
}
@@ -349,7 +344,7 @@ void btDeformableBodySolver::setupDeformableSolve(bool implicit)
}
else
{
m_dv[counter] = psb->m_nodes[j].m_v - m_backupVelocity[counter];
m_dv[counter] = psb->m_nodes[j].m_v + psb->m_nodes[j].m_splitv - m_backupVelocity[counter];
}
psb->m_nodes[j].m_v = m_backupVelocity[counter];
++counter;
@@ -441,6 +436,7 @@ void btDeformableBodySolver::predictDeformableMotion(btSoftBody* psb, btScalar d
n.m_v *= max_v;
}
n.m_q = n.m_x + n.m_v * dt;
n.m_splitv.setZero();
n.m_penetration = 0;
}

3
src/BulletSoftBody/btDeformableBodySolver.h
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@@ -67,9 +67,6 @@ public:
// solve the momentum equation
virtual void solveDeformableConstraints(btScalar solverdt);
// set up the position error in split impulse
void splitImpulseSetup(const btContactSolverInfo& infoGlobal);
// resize/clear data structures
void reinitialize(const btAlignedObjectArray<btSoftBody *>& softBodies, btScalar dt);

76
src/BulletSoftBody/btDeformableContactConstraint.cpp
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@@ -213,10 +213,18 @@ btScalar btDeformableRigidContactConstraint::solveConstraint(const btContactSolv
btVector3 va = getVa();
btVector3 vb = getVb();
btVector3 vr = vb - va;
btScalar dn = btDot(vr, cti.m_normal) + m_penetration * infoGlobal.m_deformable_erp / infoGlobal.m_timeStep;
btScalar dn = btDot(vr, cti.m_normal);
if (!infoGlobal.m_splitImpulse)
{
dn += m_penetration * infoGlobal.m_deformable_erp / infoGlobal.m_timeStep;
}
// dn is the normal component of velocity diffrerence. Approximates the residual. // todo xuchenhan@: this prob needs to be scaled by dt
btScalar residualSquare = dn*dn;
btVector3 impulse = m_contact->m_c0 * (vr + m_penetration * infoGlobal.m_deformable_erp / infoGlobal.m_timeStep * cti.m_normal) ;
btVector3 impulse = m_contact->m_c0 * vr;
if (!infoGlobal.m_splitImpulse)
{
impulse += m_contact->m_c0 * (m_penetration * infoGlobal.m_deformable_erp / infoGlobal.m_timeStep * cti.m_normal);
}
const btVector3 impulse_normal = m_contact->m_c0 * (cti.m_normal * dn);
btVector3 impulse_tangent = impulse - impulse_normal;
btVector3 old_total_tangent_dv = m_total_tangent_dv;
@@ -288,13 +296,22 @@ btScalar btDeformableRigidContactConstraint::solveConstraint(const btContactSolv
}
}
}
// va = getVa();
// vb = getVb();
// vr = vb - va;
// btScalar dn1 = btDot(vr, cti.m_normal) / 150;
// m_penetration += dn1;
return residualSquare;
}
btScalar btDeformableRigidContactConstraint::solveSplitImpulse(const btContactSolverInfo& infoGlobal)
{
const btSoftBody::sCti& cti = m_contact->m_cti;
btVector3 vb = getSplitVb();
btScalar p = m_penetration;
btScalar dn = btDot(vb, cti.m_normal) + p * infoGlobal.m_deformable_erp / infoGlobal.m_timeStep;
if (dn > 0)
return 0;
btScalar residualSquare = dn*dn;
const btVector3 impulse = 1.0/m_contact->m_c2 * (cti.m_normal * dn);
applySplitImpulse(impulse);
return residualSquare;
}
/* ================ Node vs. Rigid =================== */
btDeformableNodeRigidContactConstraint::btDeformableNodeRigidContactConstraint(const btSoftBody::DeformableNodeRigidContact& contact, const btContactSolverInfo& infoGlobal)
: m_node(contact.m_node)
@@ -313,6 +330,10 @@ btVector3 btDeformableNodeRigidContactConstraint::getVb() const
return m_node->m_v;
}
btVector3 btDeformableNodeRigidContactConstraint::getSplitVb() const
{
return m_node->m_splitv;
}
btVector3 btDeformableNodeRigidContactConstraint::getDv(const btSoftBody::Node* node) const
{
@@ -326,6 +347,13 @@ void btDeformableNodeRigidContactConstraint::applyImpulse(const btVector3& impul
contact->m_node->m_v -= dv;
}
void btDeformableNodeRigidContactConstraint::applySplitImpulse(const btVector3& impulse)
{
const btSoftBody::DeformableNodeRigidContact* contact = getContact();
btVector3 dv = impulse * contact->m_c2;
contact->m_node->m_splitv -= dv;
}
/* ================ Face vs. Rigid =================== */
btDeformableFaceRigidContactConstraint::btDeformableFaceRigidContactConstraint(const btSoftBody::DeformableFaceRigidContact& contact, const btContactSolverInfo& infoGlobal, bool useStrainLimiting)
: m_face(contact.m_face)
@@ -441,6 +469,40 @@ void btDeformableFaceRigidContactConstraint::applyImpulse(const btVector3& impul
}
}
btVector3 btDeformableFaceRigidContactConstraint::getSplitVb() const
{
const btSoftBody::DeformableFaceRigidContact* contact = getContact();
btVector3 vb = (m_face->m_n[0]->m_splitv) * contact->m_bary[0] + (m_face->m_n[1]->m_splitv) * contact->m_bary[1] + (m_face->m_n[2]->m_splitv)* contact->m_bary[2];
return vb;
}
void btDeformableFaceRigidContactConstraint::applySplitImpulse(const btVector3& impulse)
{
const btSoftBody::DeformableFaceRigidContact* contact = getContact();
btVector3 dv = impulse * contact->m_c2;
btSoftBody::Face* face = contact->m_face;
btVector3& v0 = face->m_n[0]->m_splitv;
btVector3& v1 = face->m_n[1]->m_splitv;
btVector3& v2 = face->m_n[2]->m_splitv;
const btScalar& im0 = face->m_n[0]->m_im;
const btScalar& im1 = face->m_n[1]->m_im;
const btScalar& im2 = face->m_n[2]->m_im;
if (im0 > 0)
{
v0 -= dv * contact->m_weights[0];
}
if (im1 > 0)
{
v1 -= dv * contact->m_weights[1];
}
if (im2 > 0)
{
v2 -= dv * contact->m_weights[2];
}
}
/* ================ Face vs. Node =================== */
btDeformableFaceNodeContactConstraint::btDeformableFaceNodeContactConstraint(const btSoftBody::DeformableFaceNodeContact& contact, const btContactSolverInfo& infoGlobal)
: m_node(contact.m_node)

19
src/BulletSoftBody/btDeformableContactConstraint.h
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@@ -160,12 +160,19 @@ public:
// object A is the rigid/multi body, and object B is the deformable node/face
virtual btVector3 getVa() const;
// get the split impulse velocity of the deformable face at the contact point
virtual btVector3 getSplitVb() const = 0;
virtual btScalar solveConstraint(const btContactSolverInfo& infoGlobal);
virtual void setPenetrationScale(btScalar scale)
{
m_penetration *= scale;
}
btScalar solveSplitImpulse(const btContactSolverInfo& infoGlobal);
virtual void applySplitImpulse(const btVector3& impulse) = 0;
};
//
@@ -186,6 +193,9 @@ public:
// get the velocity of the deformable node in contact
virtual btVector3 getVb() const;
// get the split impulse velocity of the deformable face at the contact point
virtual btVector3 getSplitVb() const;
// get the velocity change of the input soft body node in the constraint
virtual btVector3 getDv(const btSoftBody::Node*) const;
@@ -196,6 +206,8 @@ public:
}
virtual void applyImpulse(const btVector3& impulse);
virtual void applySplitImpulse(const btVector3& impulse);
};
//
@@ -215,9 +227,12 @@ public:
// get the velocity of the deformable face at the contact point
virtual btVector3 getVb() const;
// get the split impulse velocity of the deformable face at the contact point
virtual btVector3 getSplitVb() const;
// get the velocity change of the input soft body node in the constraint
virtual btVector3 getDv(const btSoftBody::Node*) const;
// cast the contact to the desired type
const btSoftBody::DeformableFaceRigidContact* getContact() const
{
@@ -225,6 +240,8 @@ public:
}
virtual void applyImpulse(const btVector3& impulse);
virtual void applySplitImpulse(const btVector3& impulse);
};
//

36
src/BulletSoftBody/btDeformableContactProjection.cpp
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@@ -58,23 +58,27 @@ btScalar btDeformableContactProjection::update(btCollisionObject** deformableBod
return residualSquare;
}
void btDeformableContactProjection::splitImpulseSetup(const btContactSolverInfo& infoGlobal)
btScalar btDeformableContactProjection::solveSplitImpulse(btCollisionObject** deformableBodies,int numDeformableBodies, const btContactSolverInfo& infoGlobal)
{
for (int i = 0; i < m_softBodies.size(); ++i)
{
// node constraints
for (int j = 0; j < m_nodeRigidConstraints[i].size(); ++j)
{
btDeformableNodeRigidContactConstraint& constraint = m_nodeRigidConstraints[i][j];
constraint.setPenetrationScale(infoGlobal.m_deformable_erp);
}
// face constraints
for (int j = 0; j < m_faceRigidConstraints[i].size(); ++j)
{
btDeformableFaceRigidContactConstraint& constraint = m_faceRigidConstraints[i][j];
constraint.setPenetrationScale(infoGlobal.m_deformable_erp);
}
}
btScalar residualSquare = 0;
for (int i = 0; i < numDeformableBodies; ++i)
{
for (int j = 0; j < m_softBodies.size(); ++j)
{
btCollisionObject* psb = m_softBodies[j];
if (psb != deformableBodies[i])
{
continue;
}
for (int k = 0; k < m_faceRigidConstraints[j].size(); ++k)
{
btDeformableFaceRigidContactConstraint& constraint = m_faceRigidConstraints[j][k];
btScalar localResidualSquare = constraint.solveSplitImpulse(infoGlobal);
residualSquare = btMax(residualSquare, localResidualSquare);
}
}
}
return residualSquare;
}
void btDeformableContactProjection::setConstraints(const btContactSolverInfo& infoGlobal)

2
src/BulletSoftBody/btDeformableContactProjection.h
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@@ -91,7 +91,7 @@ public:
virtual void reinitialize(bool nodeUpdated);
virtual void splitImpulseSetup(const btContactSolverInfo& infoGlobal);
btScalar solveSplitImpulse(btCollisionObject** deformableBodies,int numDeformableBodies, const btContactSolverInfo& infoGlobal);
virtual void setLagrangeMultiplier();

8
src/BulletSoftBody/btDeformableMultiBodyConstraintSolver.cpp
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@@ -21,7 +21,7 @@ btScalar btDeformableMultiBodyConstraintSolver::solveDeformableGroupIterations(b
{
{
///this is a special step to resolve penetrations (just for contacts)
solveGroupCacheFriendlySplitImpulseIterations(bodies, numBodies, manifoldPtr, numManifolds, constraints, numConstraints, infoGlobal, debugDrawer);
solveGroupCacheFriendlySplitImpulseIterations(bodies, numBodies, deformableBodies, numDeformableBodies, manifoldPtr, numManifolds, constraints, numConstraints, infoGlobal, debugDrawer);
int maxIterations = m_maxOverrideNumSolverIterations > infoGlobal.m_numIterations ? m_maxOverrideNumSolverIterations : infoGlobal.m_numIterations;
for (int iteration = 0; iteration < maxIterations; iteration++)
@@ -105,14 +105,13 @@ void btDeformableMultiBodyConstraintSolver::solverBodyWriteBack(const btContactS
}
}
void btDeformableMultiBodyConstraintSolver::solveGroupCacheFriendlySplitImpulseIterations(btCollisionObject** bodies, int numBodies, btPersistentManifold** manifoldPtr, int numManifolds, btTypedConstraint** constraints, int numConstraints, const btContactSolverInfo& infoGlobal, btIDebugDraw* debugDrawer)
void btDeformableMultiBodyConstraintSolver::solveGroupCacheFriendlySplitImpulseIterations(btCollisionObject** bodies, int numBodies, btCollisionObject** deformableBodies,int numDeformableBodies, btPersistentManifold** manifoldPtr, int numManifolds, btTypedConstraint** constraints, int numConstraints, const btContactSolverInfo& infoGlobal, btIDebugDraw* debugDrawer)
{
BT_PROFILE("solveGroupCacheFriendlySplitImpulseIterations");
int iteration;
if (infoGlobal.m_splitImpulse)
{
{
// m_deformableSolver->splitImpulseSetup(infoGlobal);
for (iteration = 0; iteration < infoGlobal.m_numIterations; iteration++)
{
btScalar leastSquaresResidual = 0.f;
@@ -128,7 +127,8 @@ void btDeformableMultiBodyConstraintSolver::solveGroupCacheFriendlySplitImpulseI
}
// solve the position correction between deformable and rigid/multibody
// btScalar residual = m_deformableSolver->solveSplitImpulse(infoGlobal);
// leastSquaresResidual = btMax(leastSquaresResidual, residual * residual);
btScalar residual = m_deformableSolver->m_objective->m_projection.solveSplitImpulse(deformableBodies, numDeformableBodies, infoGlobal);
leastSquaresResidual = btMax(leastSquaresResidual, residual * residual);
}
if (leastSquaresResidual <= infoGlobal.m_leastSquaresResidualThreshold || iteration >= (infoGlobal.m_numIterations - 1))
{

2
src/BulletSoftBody/btDeformableMultiBodyConstraintSolver.h
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@@ -44,7 +44,7 @@ protected:
// write the velocity of the underlying rigid body to the the the solver body
void writeToSolverBody(btCollisionObject** bodies, int numBodies, const btContactSolverInfo& infoGlobal);
virtual void solveGroupCacheFriendlySplitImpulseIterations(btCollisionObject** bodies, int numBodies, btPersistentManifold** manifoldPtr, int numManifolds, btTypedConstraint** constraints, int numConstraints, const btContactSolverInfo& infoGlobal, btIDebugDraw* debugDrawer);
virtual void solveGroupCacheFriendlySplitImpulseIterations(btCollisionObject** bodies, int numBodies, btCollisionObject** deformableBodies,int numDeformableBodies, btPersistentManifold** manifoldPtr, int numManifolds, btTypedConstraint** constraints, int numConstraints, const btContactSolverInfo& infoGlobal, btIDebugDraw* debugDrawer);
virtual btScalar solveDeformableGroupIterations(btCollisionObject** bodies,int numBodies,btCollisionObject** deformableBodies,int numDeformableBodies,btPersistentManifold** manifoldPtr, int numManifolds,btTypedConstraint** constraints,int numConstraints,const btContactSolverInfo& infoGlobal,btIDebugDraw* debugDrawer);
public:

2
src/BulletSoftBody/btDeformableMultiBodyDynamicsWorld.cpp
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@@ -315,7 +315,7 @@ void btDeformableMultiBodyDynamicsWorld::integrateTransforms(btScalar timeStep)
node.m_v[c] = -clampDeltaV;
}
}
node.m_x = node.m_x + timeStep * node.m_v;
node.m_x = node.m_x + timeStep * (node.m_v + node.m_splitv);
node.m_q = node.m_x;
node.m_vn = node.m_v;
}

5
src/BulletSoftBody/btSoftBody.h
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@@ -271,7 +271,8 @@ public:
btDbvtNode* m_leaf; // Leaf data
btScalar m_penetration; // depth of penetration
int m_battach : 1; // Attached
int index;
int index;
btVector3 m_splitv; // velocity associated with split impulse
};
/* Link */
ATTRIBUTE_ALIGNED16(struct)
@@ -296,7 +297,7 @@ public:
btDbvtNode* m_leaf; // Leaf data
btVector4 m_pcontact; // barycentric weights of the persistent contact
btVector3 m_n0, m_n1, m_vn;
int m_index;
int m_index;
};
/* Tetra */
struct Tetra : Feature