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add option for angular momentum conserving damping for mass spring

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This commit is contained in:
Xuchen Han
2019-08-15 17:15:36 -07:00
parent bedaa760c2
commit f8c60e9e3c
1 changed files with 20 additions and 3 deletions
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23
src/BulletSoftBody/btDeformableMassSpringForce.h
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@@ -18,10 +18,10 @@
class btDeformableMassSpringForce : public btDeformableLagrangianForce
{
bool m_momentum_conserving;
public:
// using TVStack = btDeformableLagrangianForce::TVStack;
typedef btAlignedObjectArray<btVector3> TVStack;
btDeformableMassSpringForce()
btDeformableMassSpringForce() : m_momentum_conserving(false)
{
}
@@ -53,7 +53,15 @@ public:
// damping force
btVector3 v_diff = (node2->m_v - node1->m_v);
btScalar k_damp = psb->m_dampingCoefficient;
btVector3 scaled_force = scale * v_diff * k_damp;
btVector3 scaled_force = scale * k_damp * v_diff;
if (m_momentum_conserving)
{
if ((node2->m_q - node1->m_q).norm() > SIMD_EPSILON)
{
btVector3 dir = (node2->m_q - node1->m_q).normalized();
scaled_force = scale * k_damp * v_diff.dot(dir) * dir;
}
}
force[id1] += scaled_force;
force[id2] -= scaled_force;
}
@@ -102,7 +110,16 @@ public:
btSoftBody::Node* node2 = link.m_n[1];
size_t id1 = node1->index;
size_t id2 = node2->index;
btVector3 local_scaled_df = scaled_k_damp * (dv[id2] - dv[id1]);
if (m_momentum_conserving)
{
if ((node2->m_q - node1->m_q).norm() > SIMD_EPSILON)
{
btVector3 dir = (node2->m_q - node1->m_q).normalized();
local_scaled_df= scaled_k_damp * (dv[id2] - dv[id1]).dot(dir) * dir;
}
}
df[id1] += local_scaled_df;
df[id2] -= local_scaled_df;
}