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add strain limiting to face contact to improve stability

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This commit is contained in:
Xuchen Han
2019-10-25 17:28:21 -07:00
parent 41eb074406
commit ec1ef0c465
1 changed files with 49 additions and 12 deletions
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61
src/BulletSoftBody/btDeformableContactConstraint.cpp
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@@ -361,12 +361,32 @@ void btDeformableFaceRigidContactConstraint::applyImpulse(const btVector3& impul
const btSoftBody::DeformableFaceRigidContact* contact = getContact();
btVector3 dv = impulse * contact->m_c2;
btSoftBody::Face* face = contact->m_face;
if (face->m_n[0]->m_im > 0)
face->m_n[0]->m_v -= dv * contact->m_weights[0];
if (face->m_n[1]->m_im > 0)
face->m_n[1]->m_v -= dv * contact->m_weights[1];
if (face->m_n[2]->m_im > 0)
face->m_n[2]->m_v -= dv * contact->m_weights[2];
btVector3& v0 = face->m_n[0]->m_v;
btVector3& v1 = face->m_n[1]->m_v;
btVector3& v2 = face->m_n[2]->m_v;
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];
// apply strain limiting to prevent undamped modes
btScalar m01 = (btScalar(1)/(im0 + im1));
btScalar m02 = (btScalar(1)/(im0 + im2));
btScalar m12 = (btScalar(1)/(im1 + im2));
btVector3 dv0 = im0 * (m01 * (v1-v0) + m02 * (v2-v0));
btVector3 dv1 = im1 * (m01 * (v0-v1) + m12 * (v2-v1));
btVector3 dv2 = im2 * (m12 * (v1-v2) + m02 * (v0-v2));
v0 += dv0;
v1 += dv1;
v2 += dv2;
}
/* ================ Face vs. Node =================== */
@@ -482,16 +502,33 @@ void btDeformableFaceNodeContactConstraint::applyImpulse(const btVector3& impuls
}
btSoftBody::Face* face = contact->m_face;
if (face->m_n[0]->m_im > 0)
btVector3& v0 = face->m_n[0]->m_v;
btVector3& v1 = face->m_n[1]->m_v;
btVector3& v2 = face->m_n[2]->m_v;
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)
{
face->m_n[0]->m_v -= dvb * contact->m_weights[0];
v0 -= dvb * contact->m_weights[0];
}
if (face->m_n[1]->m_im > 0)
if (im1 > 0)
{
face->m_n[1]->m_v -= dvb * contact->m_weights[1];
v1 -= dvb * contact->m_weights[1];
}
if (face->m_n[2]->m_im > 0)
if (im2 > 0)
{
face->m_n[2]->m_v -= dvb * contact->m_weights[2];
v2 -= dvb * contact->m_weights[2];
}
// todo: Face node constraints needs more work
// btScalar m01 = (btScalar(1)/(im0 + im1));
// btScalar m02 = (btScalar(1)/(im0 + im2));
// btScalar m12 = (btScalar(1)/(im1 + im2));
//
// btVector3 dv0 = im0 * (m01 * (v1-v0) + m02 * (v2-v0));
// btVector3 dv1 = im1 * (m01 * (v0-v1) + m12 * (v2-v1));
// btVector3 dv2 = im2 * (m12 * (v1-v2) + m02 * (v0-v2));
// v0 += dv0;
// v1 += dv1;
// v2 += dv2;
}