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add strain rate limiting

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This commit is contained in:
Xuchen Han
2019-12-31 14:04:18 -08:00
parent 79c1343b6a
commit d7442cee21
10 changed files with 116 additions and 79 deletions
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87
src/BulletSoftBody/btDeformableContactConstraint.cpp
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@@ -15,9 +15,9 @@
#include "btDeformableContactConstraint.h"
/* ================ Deformable Node Anchor =================== */
btDeformableNodeAnchorConstraint::btDeformableNodeAnchorConstraint(const btSoftBody::DeformableNodeRigidAnchor& a)
btDeformableNodeAnchorConstraint::btDeformableNodeAnchorConstraint(const btSoftBody::DeformableNodeRigidAnchor& a, const btContactSolverInfo& infoGlobal)
: m_anchor(&a)
, btDeformableContactConstraint(a.m_cti.m_normal)
, btDeformableContactConstraint(a.m_cti.m_normal, infoGlobal)
{
}
@@ -134,9 +134,9 @@ void btDeformableNodeAnchorConstraint::applyImpulse(const btVector3& impulse)
}
/* ================ Deformable vs. Rigid =================== */
btDeformableRigidContactConstraint::btDeformableRigidContactConstraint(const btSoftBody::DeformableRigidContact& c)
btDeformableRigidContactConstraint::btDeformableRigidContactConstraint(const btSoftBody::DeformableRigidContact& c, const btContactSolverInfo& infoGlobal)
: m_contact(&c)
, btDeformableContactConstraint(c.m_cti.m_normal)
, btDeformableContactConstraint(c.m_cti.m_normal, infoGlobal)
{
m_total_normal_dv.setZero();
m_total_tangent_dv.setZero();
@@ -321,9 +321,9 @@ btScalar btDeformableRigidContactConstraint::solveSplitImpulse(const btContactSo
}
/* ================ Node vs. Rigid =================== */
btDeformableNodeRigidContactConstraint::btDeformableNodeRigidContactConstraint(const btSoftBody::DeformableNodeRigidContact& contact)
btDeformableNodeRigidContactConstraint::btDeformableNodeRigidContactConstraint(const btSoftBody::DeformableNodeRigidContact& contact, const btContactSolverInfo& infoGlobal)
: m_node(contact.m_node)
, btDeformableRigidContactConstraint(contact)
, btDeformableRigidContactConstraint(contact, infoGlobal)
{
}
@@ -359,9 +359,9 @@ void btDeformableNodeRigidContactConstraint::applySplitImpulse(const btVector3&
};
/* ================ Face vs. Rigid =================== */
btDeformableFaceRigidContactConstraint::btDeformableFaceRigidContactConstraint(const btSoftBody::DeformableFaceRigidContact& contact)
btDeformableFaceRigidContactConstraint::btDeformableFaceRigidContactConstraint(const btSoftBody::DeformableFaceRigidContact& contact, const btContactSolverInfo& infoGlobal)
: m_face(contact.m_face)
, btDeformableRigidContactConstraint(contact)
, btDeformableRigidContactConstraint(contact, infoGlobal)
{
}
@@ -413,19 +413,60 @@ void btDeformableFaceRigidContactConstraint::applyImpulse(const btVector3& impul
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;
// apply strain limiting to prevent the new velocity to change the current length of the edge by more than 1%.
btScalar p = 0.01;
btVector3& x0 = face->m_n[0]->m_x;
btVector3& x1 = face->m_n[1]->m_x;
btVector3& x2 = face->m_n[2]->m_x;
const btVector3 x_diff[3] = {x1-x0, x2-x0, x2-x1};
const btVector3 v_diff[3] = {v1-v0, v2-v0, v2-v1};
btVector3 u[3];
btScalar x_diff_dot_u, dn[3];
btScalar dt = m_infoGlobal->m_timeStep;
for (int i = 0; i < 3; ++i)
{
btScalar x_diff_norm = x_diff[i].safeNorm();
btScalar x_diff_norm_new = (x_diff[i] + v_diff[i] * dt).safeNorm();
btScalar strainRate = x_diff_norm_new/x_diff_norm;
u[i] = v_diff[i];
u[i].safeNormalize();
if (x_diff_norm == 0 || (1-p <= strainRate && strainRate <= 1+p))
{
dn[i] = 0;
continue;
}
x_diff_dot_u = btDot(x_diff[i], u[i]);
btScalar s;
if (1-p > strainRate)
{
s = 1/dt * (-x_diff_dot_u - btSqrt(x_diff_dot_u*x_diff_dot_u + (p*p-2*p) * x_diff_norm * x_diff_norm));
}
else
{
s = 1/dt * (-x_diff_dot_u + btSqrt(x_diff_dot_u*x_diff_dot_u + (p*p+2*p) * x_diff_norm * x_diff_norm));
}
// x_diff_norm_new = (x_diff[i] + s * u[i] * dt).safeNorm();
// strainRate = x_diff_norm_new/x_diff_norm;
dn[i] = s - v_diff[i].safeNorm();
}
btScalar relaxation = 0.5;
// apply strain limiting to prevent undamped modes
btScalar m01 = (relaxation/(im0 + im1));
btScalar m02 = (relaxation/(im0 + im2));
btScalar m12 = (relaxation/(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));
btVector3 dv0 = im0 * (m01 * u[0]*(-dn[0]) + m02 * u[1]*-(dn[1]));
btVector3 dv1 = im1 * (m01 * u[0]*(dn[0]) + m12 * u[2]*(-dn[2]));
btVector3 dv2 = im2 * (m12 * u[2]*(dn[2]) + m02 * u[1]*(dn[1]));
v0 += dv0;
v1 += dv1;
v2 += dv2;
}
void btDeformableFaceRigidContactConstraint::applySplitImpulse(const btVector3& impulse)
@@ -449,11 +490,11 @@ void btDeformableFaceRigidContactConstraint::applySplitImpulse(const btVector3&
}
/* ================ Face vs. Node =================== */
btDeformableFaceNodeContactConstraint::btDeformableFaceNodeContactConstraint(const btSoftBody::DeformableFaceNodeContact& contact)
btDeformableFaceNodeContactConstraint::btDeformableFaceNodeContactConstraint(const btSoftBody::DeformableFaceNodeContact& contact, const btContactSolverInfo& infoGlobal)
: m_node(contact.m_node)
, m_face(contact.m_face)
, m_contact(&contact)
, btDeformableContactConstraint(contact.m_normal)
, btDeformableContactConstraint(contact.m_normal, infoGlobal)
{
m_total_normal_dv.setZero();
m_total_tangent_dv.setZero();