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add elastic and damping stiffness of spring into the force class

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This commit is contained in:
Xuchen Han
2019-08-15 17:47:28 -07:00
parent df7f216bf8
commit aa4d5bda3e
1 changed files with 9 additions and 7 deletions
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16
src/BulletSoftBody/btDeformableMassSpringForce.h
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@@ -19,9 +19,13 @@
class btDeformableMassSpringForce : public btDeformableLagrangianForce
{
bool m_momentum_conserving;
btScalar m_elasticStiffness, m_dampingStiffness;
public:
typedef btAlignedObjectArray<btVector3> TVStack;
btDeformableMassSpringForce() : m_momentum_conserving(false)
btDeformableMassSpringForce() : m_momentum_conserving(false), m_elasticStiffness(1), m_dampingStiffness(0.05)
{
}
btDeformableMassSpringForce(btScalar k, btScalar d, bool conserve_angular = false) : m_momentum_conserving(conserve_angular), m_elasticStiffness(k), m_dampingStiffness(d)
{
}
@@ -52,14 +56,13 @@ public:
// damping force
btVector3 v_diff = (node2->m_v - node1->m_v);
btScalar k_damp = psb->m_dampingCoefficient;
btVector3 scaled_force = scale * k_damp * v_diff;
btVector3 scaled_force = scale * m_dampingStiffness * 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;
scaled_force = scale * m_dampingStiffness * v_diff.dot(dir) * dir;
}
}
force[id1] += scaled_force;
@@ -80,7 +83,6 @@ public:
const btSoftBody::Link& link = psb->m_links[j];
btSoftBody::Node* node1 = link.m_n[0];
btSoftBody::Node* node2 = link.m_n[1];
btScalar kLST = link.Feature::m_material->m_kLST;
btScalar r = link.m_rl;
size_t id1 = node1->index;
size_t id2 = node2->index;
@@ -89,7 +91,7 @@ public:
// explicit elastic force
btVector3 dir = (node2->m_q - node1->m_q);
btVector3 dir_normalized = dir.normalized();
btVector3 scaled_force = scale * kLST * (dir - dir_normalized * r);
btVector3 scaled_force = scale * m_elasticStiffness * (dir - dir_normalized * r);
force[id1] += scaled_force;
force[id2] -= scaled_force;
}
@@ -102,7 +104,7 @@ public:
for (int i = 0; i < m_softBodies.size(); ++i)
{
const btSoftBody* psb = m_softBodies[i];
btScalar scaled_k_damp = psb->m_dampingCoefficient * scale;
btScalar scaled_k_damp = m_dampingStiffness * scale;
for (int j = 0; j < psb->m_links.size(); ++j)
{
const btSoftBody::Link& link = psb->m_links[j];