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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(); int numNodes = getNumNodes();
btAssert(numNodes <= force.size()) btAssert(numNodes <= force.size())
btVector3 grad_N_hat_1st_col = btVector3(-1,-1,-1);
for (int i = 0; i < m_softBodies.size(); ++i) for (int i = 0; i < m_softBodies.size(); ++i)
{ {
btSoftBody* psb = m_softBodies[i]; btSoftBody* psb = m_softBodies[i];
@@ -64,8 +65,7 @@ public:
btMatrix3x3 F = tetra.m_ds * tetra.m_Dm_inverse; btMatrix3x3 F = tetra.m_ds * tetra.m_Dm_inverse;
btMatrix3x3 P; btMatrix3x3 P;
firstPiola(F,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(); btMatrix3x3 force_on_node123 = P * tetra.m_Dm_inverse.transpose();
btSoftBody::Node* node0 = tetra.m_n[0]; btSoftBody::Node* node0 = tetra.m_n[0];
@@ -79,26 +79,30 @@ public:
// elastic force // elastic force
// explicit elastic force // explicit elastic force
force[id0] -= scale * tetra.m_element_measure * force_on_node0; btScalar scale1 = scale * tetra.m_element_measure;
force[id1] -= scale * tetra.m_element_measure * force_on_node123.getColumn(0); force[id0] -= scale1 * force_on_node0;
force[id2] -= scale * tetra.m_element_measure * force_on_node123.getColumn(1); force[id1] -= scale1 * force_on_node123.getColumn(0);
force[id3] -= scale * tetra.m_element_measure * force_on_node123.getColumn(2); force[id2] -= scale1 * force_on_node123.getColumn(1);
force[id3] -= scale1 * force_on_node123.getColumn(2);
} }
} }
} }
void firstPiola(const btMatrix3x3& F, btMatrix3x3& P) void firstPiola(const btMatrix3x3& F, btMatrix3x3& P)
{ {
btMatrix3x3 R,S; // btMatrix3x3 JFinvT = F.adjoint();
btScalar J = F.determinant(); btScalar J = F.determinant();
P = F.adjoint() * (m_lambda * (J-1));
if (m_mu > SIMD_EPSILON)
{
btMatrix3x3 R,S;
if (J < 1024 * SIMD_EPSILON) if (J < 1024 * SIMD_EPSILON)
R.setIdentity(); R.setIdentity();
else else
PolarDecompose(F, R, S); // this QR is not robust, consider using implicit shift svd PolarDecompose(F, R, S); // this QR is not robust, consider using implicit shift svd
/*https://fuchuyuan.github.io/research/svd/paper.pdf*/ /*https://fuchuyuan.github.io/research/svd/paper.pdf*/
P += (F-R) * 2 * m_mu;
btMatrix3x3 JFinvT = F.adjoint(); }
P = JFinvT * (m_lambda * (J-1)) + (F-R) * 2 * m_mu;
} }
void updateDs(btSoftBody::Tetra& t) void updateDs(btSoftBody::Tetra& t)
{ {