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bug fixes for face contact to prevent sticking

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This commit is contained in:
Xuchen Han
2019-12-27 12:43:08 -08:00
parent 6a8973d2f4
commit 65b75e5937
4 changed files with 39 additions and 18 deletions
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2
src/BulletDynamics/ConstraintSolver/btContactSolverInfo.h
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@@ -82,7 +82,7 @@ struct btContactSolverInfo : public btContactSolverInfoData
m_numIterations = 10;
m_erp = btScalar(0.2);
m_erp2 = btScalar(0.2);
m_deformable_erp = btScalar(0.);
m_deformable_erp = btScalar(1.0);
m_globalCfm = btScalar(0.);
m_frictionERP = btScalar(0.2); //positional friction 'anchors' are disabled by default
m_frictionCFM = btScalar(0.);

6
src/BulletSoftBody/btDeformableContactConstraint.cpp
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@@ -140,8 +140,8 @@ btDeformableRigidContactConstraint::btDeformableRigidContactConstraint(const btS
{
m_total_normal_dv.setZero();
m_total_tangent_dv.setZero();
// penetration is non-positive. The magnitude of penetration is the depth of penetration.
m_penetration = btMin(btScalar(0), c.m_cti.m_offset);
// The magnitude of penetration is the depth of penetration.
m_penetration = c.m_cti.m_offset;
}
btDeformableRigidContactConstraint::btDeformableRigidContactConstraint(const btDeformableRigidContactConstraint& other)
@@ -256,6 +256,8 @@ btScalar btDeformableRigidContactConstraint::solveConstraint()
impulse = impulse_normal + impulse_tangent;
// apply impulse to deformable nodes involved and change their velocities
applyImpulse(impulse);
if (residualSquare < 1e-7)
return residualSquare;
// apply impulse to the rigid/multibodies involved and change their velocities
if (cti.m_colObj->getInternalType() == btCollisionObject::CO_RIGID_BODY)
{

41
src/BulletSoftBody/btSoftBody.cpp
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@@ -53,6 +53,7 @@ btSoftBody::btSoftBody(btSoftBodyWorldInfo* worldInfo, int node_count, const btV
n.m_material = pm;
}
updateBounds();
setCollisionQuadrature(3);
}
btSoftBody::btSoftBody(btSoftBodyWorldInfo* worldInfo)
@@ -2403,10 +2404,10 @@ bool btSoftBody::checkDeformableContact(const btCollisionObjectWrapper* colObjWr
const btCollisionObject* tmpCollisionObj = colObjWrap->getCollisionObject();
// use the position x_{n+1}^* = x_n + dt * v_{n+1}^* where v_{n+1}^* = v_n + dtg for collision detect
// but resolve contact at x_n
// btTransform wtr = (predict) ?
// (colObjWrap->m_preTransform != NULL ? tmpCollisionObj->getInterpolationWorldTransform()*(*colObjWrap->m_preTransform) : tmpCollisionObj->getInterpolationWorldTransform())
// : colObjWrap->getWorldTransform();
const btTransform& wtr = colObjWrap->getWorldTransform();
btTransform wtr = (predict) ?
(colObjWrap->m_preTransform != NULL ? tmpCollisionObj->getInterpolationWorldTransform()*(*colObjWrap->m_preTransform) : tmpCollisionObj->getInterpolationWorldTransform())
: colObjWrap->getWorldTransform();
// const btTransform& wtr = colObjWrap->getWorldTransform();
btScalar dst =
m_worldInfo->m_sparsesdf.Evaluate(
wtr.invXform(x),
@@ -2460,7 +2461,7 @@ bool btSoftBody::checkDeformableFaceContact(const btCollisionObjectWrapper* colO
// const btTransform& wtr = colObjWrap->getWorldTransform();
btScalar dst;
//#define USE_QUADRATURE 1
#define USE_QUADRATURE 1
//#define CACHE_PREV_COLLISION
// use the contact position of the previous collision
@@ -2476,6 +2477,7 @@ bool btSoftBody::checkDeformableFaceContact(const btCollisionObjectWrapper* colO
nrm,
margin);
nrm = wtr.getBasis() * nrm;
cti.m_colObj = colObjWrap->getCollisionObject();
// use cached contact point
}
else
@@ -2492,10 +2494,11 @@ bool btSoftBody::checkDeformableFaceContact(const btCollisionObjectWrapper* colO
contact_point = results.witnesses[0];
getBarycentric(contact_point, f.m_n[0]->m_x, f.m_n[1]->m_x, f.m_n[2]->m_x, bary);
nrm = results.normal;
cti.m_colObj = colObjWrap->getCollisionObject();
for (int i = 0; i < 3; ++i)
f.m_pcontact[i] = bary[i];
}
return (dst < 0);
#endif
// use collision quadrature point
@@ -2505,7 +2508,11 @@ bool btSoftBody::checkDeformableFaceContact(const btCollisionObjectWrapper* colO
btVector3 local_nrm;
for (int q = 0; q < m_quads.size(); ++q)
{
btVector3 p = BaryEval(f.m_n[0]->m_x, f.m_n[1]->m_x, f.m_n[2]->m_x, m_quads[q]);
btVector3 p;
if (predict)
p = BaryEval(f.m_n[0]->m_q, f.m_n[1]->m_q, f.m_n[2]->m_q, m_quads[q]);
else
p = BaryEval(f.m_n[0]->m_x, f.m_n[1]->m_x, f.m_n[2]->m_x, m_quads[q]);
btScalar local_dst = m_worldInfo->m_sparsesdf.Evaluate(
wtr.invXform(p),
shp,
@@ -2513,12 +2520,21 @@ bool btSoftBody::checkDeformableFaceContact(const btCollisionObjectWrapper* colO
margin);
if (local_dst < dst)
{
if (local_dst < 0 && predict)
return true;
dst = local_dst;
contact_point = p;
bary = m_quads[q];
nrm = wtr.getBasis() * local_nrm;
nrm = local_nrm;
}
if (!predict)
{
cti.m_colObj = colObjWrap->getCollisionObject();
cti.m_normal = wtr.getBasis() * nrm;
cti.m_offset = dst;
}
}
return (dst < 0);
}
#endif
@@ -2530,6 +2546,11 @@ bool btSoftBody::checkDeformableFaceContact(const btCollisionObjectWrapper* colO
triangle_transform.setOrigin(f.m_n[0]->m_x);
btTriangleShape triangle(btVector3(0,0,0), f.m_n[1]->m_x-f.m_n[0]->m_x, f.m_n[2]->m_x-f.m_n[0]->m_x);
btVector3 guess(0,0,0);
if (predict)
{
triangle_transform.setOrigin(f.m_n[0]->m_q);
triangle = btTriangleShape(btVector3(0,0,0), f.m_n[1]->m_q-f.m_n[0]->m_q, f.m_n[2]->m_q-f.m_n[0]->m_q);
}
const btConvexShape* csh = static_cast<const btConvexShape*>(shp);
btGjkEpaSolver2::SignedDistance(&triangle, triangle_transform, csh, wtr, guess, results);
dst = results.distance - margin;
@@ -2547,9 +2568,7 @@ bool btSoftBody::checkDeformableFaceContact(const btCollisionObjectWrapper* colO
cti.m_offset = dst;
}
if (dst < 0)
return true;
return (false);
return (dst < 0);
}
//

8
src/BulletSoftBody/btSoftBodyInternals.h
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@@ -1070,8 +1070,8 @@ struct btSoftColliders
if (!n.m_battach)
{
// check for collision at x_{n+1}^* as well at x_n
if (psb->checkDeformableContact(m_colObj1Wrap, n.m_x, m, c.m_cti, /*predict = */ true) || psb->checkDeformableContact(m_colObj1Wrap, n.m_q, m, c.m_cti, /*predict = */ true))
// check for collision at x_{n+1}^*
if (psb->checkDeformableContact(m_colObj1Wrap, n.m_q, m, c.m_cti, /*predict = */ true))
{
const btScalar ima = n.m_im;
// todo: collision between multibody and fixed deformable node will be missed.
@@ -1159,7 +1159,6 @@ struct btSoftColliders
btSoftBody::Node* n0 = f.m_n[0];
btSoftBody::Node* n1 = f.m_n[1];
btSoftBody::Node* n2 = f.m_n[2];
const btScalar m = (n0->m_im > 0 && n1->m_im > 0 && n2->m_im > 0 )? dynmargin : stamargin;
btSoftBody::DeformableFaceRigidContact c;
btVector3 contact_point;
@@ -1181,7 +1180,8 @@ struct btSoftColliders
// todo xuchenhan@: this is assuming mass of all vertices are the same. Need to modify if mass are different for distinct vertices
c.m_weights = btScalar(2)/(btScalar(1) + bary.length2()) * bary;
c.m_face = &f;
const btScalar fc = psb->m_cfg.kDF * m_colObj1Wrap->getCollisionObject()->getFriction();
// friction is handled by the nodes to prevent sticking
const btScalar fc = 0;
// the effective inverse mass of the face as in https://graphics.stanford.edu/papers/cloth-sig02/cloth.pdf
ima = bary.getX()*c.m_weights.getX() * n0->m_im + bary.getY()*c.m_weights.getY() * n1->m_im + bary.getZ()*c.m_weights.getZ() * n2->m_im;