deformable code refactor

src/BulletSoftBody/btDeformableBackwardEulerObjective.cpp

@@ -0,0 +1,134 @@
+//
+//  btDeformableBackwardEulerObjective.cpp
+//  BulletSoftBody
+//
+//  Created by Xuchen Han on 7/9/19.
+//
+
+#include "btDeformableBackwardEulerObjective.h"
+
+btDeformableBackwardEulerObjective::btDeformableBackwardEulerObjective(btAlignedObjectArray<btSoftBody *>& softBodies, const TVStack& backup_v)
+: m_softBodies(softBodies)
+, projection(m_softBodies, m_dt)
+, m_backupVelocity(backup_v)
+{
+    // TODO: this should really be specified in initialization instead of here
+    btDeformableMassSpringForce* mass_spring = new btDeformableMassSpringForce(m_softBodies);
+    btDeformableGravityForce* gravity = new btDeformableGravityForce(m_softBodies, btVector3(0,-10,0));
+    m_preconditioner = new DefaultPreconditioner();
+    m_lf.push_back(mass_spring);
+    m_lf.push_back(gravity);
+}
+
+void btDeformableBackwardEulerObjective::reinitialize(bool nodeUpdated)
+{
+    if(nodeUpdated)
+    {
+        projection.setSoftBodies(m_softBodies);
+    }
+    for (int i = 0; i < m_lf.size(); ++i)
+    {
+        m_lf[i]->reinitialize(nodeUpdated);
+    }
+    projection.reinitialize(nodeUpdated);
+    m_preconditioner->reinitialize(nodeUpdated);
+}
+
+void btDeformableBackwardEulerObjective::setDt(btScalar dt)
+{
+    m_dt = dt;
+}
+
+void btDeformableBackwardEulerObjective::multiply(const TVStack& x, TVStack& b) const
+{
+    for (int i = 0; i < b.size(); ++i)
+        b[i].setZero();
+    
+    // add in the mass term
+    size_t counter = 0;
+    for (int i = 0; i < m_softBodies.size(); ++i)
+    {
+        btSoftBody* psb = m_softBodies[i];
+        for (int j = 0; j < psb->m_nodes.size(); ++j)
+        {
+            const auto& node = psb->m_nodes[j];
+            b[counter] += (node.m_im == 0) ? btVector3(0,0,0) : x[counter] / node.m_im;
+            ++counter;
+        }
+    }
+    
+    for (int i = 0; i < m_lf.size(); ++i)
+    {
+        // add damping matrix
+        m_lf[i]->addScaledForceDifferential(-m_dt, x, b);
+    }
+}
+
+void btDeformableBackwardEulerObjective::updateVelocity(const TVStack& dv)
+{
+    // only the velocity of the constrained nodes needs to be updated during CG solve
+    for (auto it : projection.m_constraints)
+    {
+        int i = projection.m_indices[it.first];
+        it.first->m_v = m_backupVelocity[i] + dv[i];
+    }
+}
+
+void btDeformableBackwardEulerObjective::applyForce(TVStack& force, bool setZero)
+{
+    size_t counter = 0;
+    for (int i = 0; i < m_softBodies.size(); ++i)
+    {
+        btSoftBody* psb = m_softBodies[i];
+        for (int j = 0; j < psb->m_nodes.size(); ++j)
+        {
+            btScalar one_over_mass = (psb->m_nodes[j].m_im == 0) ? 0 : psb->m_nodes[j].m_im;
+            psb->m_nodes[j].m_v += one_over_mass * force[counter++];
+        }
+    }
+    if (setZero)
+    {
+        for (int i = 0; i < force.size(); ++i)
+            force[i].setZero();
+    }
+}
+
+void btDeformableBackwardEulerObjective::computeResidual(btScalar dt, TVStack &residual) const
+{
+    // add implicit force
+    for (int i = 0; i < m_lf.size(); ++i)
+    {
+        m_lf[i]->addScaledImplicitForce(dt, residual);
+    }
+}
+
+btScalar btDeformableBackwardEulerObjective::computeNorm(const TVStack& residual) const
+{
+    btScalar norm_squared = 0;
+    for (int i = 0; i < residual.size(); ++i)
+    {
+        norm_squared += residual[i].length2();
+    }
+    return std::sqrt(norm_squared+SIMD_EPSILON);
+}
+
+void btDeformableBackwardEulerObjective::applyExplicitForce(TVStack& force)
+{
+    for (int i = 0; i < m_lf.size(); ++i)
+        m_lf[i]->addScaledExplicitForce(m_dt, force);
+    applyForce(force, true);
+}
+
+void btDeformableBackwardEulerObjective::initialGuess(TVStack& dv, const TVStack& residual)
+{
+    size_t counter = 0;
+    for (int i = 0; i < m_softBodies.size(); ++i)
+    {
+        btSoftBody* psb = m_softBodies[i];
+        for (int j = 0; j < psb->m_nodes.size(); ++j)
+        {
+            dv[counter] = psb->m_nodes[j].m_im * residual[counter];
+            ++counter;
+        }
+    }
+}