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speed up corotated force computation

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This commit is contained in:
Xuchen Han
2019-08-14 10:28:34 -07:00
parent fce1296413
commit bedaa760c2
1 changed files with 19 additions and 15 deletions
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24
src/BulletSoftBody/btDeformableCorotatedForce.h
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@@ -54,6 +54,7 @@ public:
{
int numNodes = getNumNodes();
btAssert(numNodes <= force.size())
btVector3 grad_N_hat_1st_col = btVector3(-1,-1,-1);
for (int i = 0; i < m_softBodies.size(); ++i)
{
btSoftBody* psb = m_softBodies[i];
@@ -64,8 +65,7 @@ public:
btMatrix3x3 F = tetra.m_ds * tetra.m_Dm_inverse;
btMatrix3x3 P;
firstPiola(F,P);
btVector3 grad_N_hat_1st_col = btVector3(-1,-1,-1);
btVector3 force_on_node0 = P * tetra.m_Dm_inverse.transpose()*grad_N_hat_1st_col;
btVector3 force_on_node0 = P * (tetra.m_Dm_inverse.transpose()*grad_N_hat_1st_col);
btMatrix3x3 force_on_node123 = P * tetra.m_Dm_inverse.transpose();
btSoftBody::Node* node0 = tetra.m_n[0];
@@ -79,26 +79,30 @@ public:
// elastic force
// explicit elastic force
force[id0] -= scale * tetra.m_element_measure * force_on_node0;
force[id1] -= scale * tetra.m_element_measure * force_on_node123.getColumn(0);
force[id2] -= scale * tetra.m_element_measure * force_on_node123.getColumn(1);
force[id3] -= scale * tetra.m_element_measure * force_on_node123.getColumn(2);
btScalar scale1 = scale * tetra.m_element_measure;
force[id0] -= scale1 * force_on_node0;
force[id1] -= scale1 * force_on_node123.getColumn(0);
force[id2] -= scale1 * force_on_node123.getColumn(1);
force[id3] -= scale1 * force_on_node123.getColumn(2);
}
}
}
void firstPiola(const btMatrix3x3& F, btMatrix3x3& P)
{
btMatrix3x3 R,S;
// btMatrix3x3 JFinvT = F.adjoint();
btScalar J = F.determinant();
P = F.adjoint() * (m_lambda * (J-1));
if (m_mu > SIMD_EPSILON)
{
btMatrix3x3 R,S;
if (J < 1024 * SIMD_EPSILON)
R.setIdentity();
else
PolarDecompose(F, R, S); // this QR is not robust, consider using implicit shift svd
/*https://fuchuyuan.github.io/research/svd/paper.pdf*/
btMatrix3x3 JFinvT = F.adjoint();
P = JFinvT * (m_lambda * (J-1)) + (F-R) * 2 * m_mu;
P += (F-R) * 2 * m_mu;
}
}
void updateDs(btSoftBody::Tetra& t)
{