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add check for momentum conservation

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This commit is contained in:
jingyuc
2021-08-26 13:41:26 -04:00
parent f26e3d133d
commit 3e76b11d46
1 changed files with 47 additions and 7 deletions
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54
examples/ReducedDeformableDemo/BasicTest.cpp
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@@ -93,21 +93,61 @@ public:
btRigidBody* rb = createRigidBody(mass, startTransform, shape);
rb->setLinearVelocity(btVector3(0,+COLLIDING_VELOCITY, 0));
}
void checkMomentum(btReducedSoftBody* rsb)
{
btVector3 x_com(0, 0, 0);
btVector3 total_linear(0, 0, 0);
btVector3 total_angular(0, 0, 0);
{
std::ofstream myfile("center_of_mass.txt", std::ios_base::app);
for (int i = 0; i < rsb->m_nFull; ++i)
{
x_com += rsb->m_nodalMass[i] * rsb->m_nodes[i].m_x;
}
x_com /= rsb->getTotalMass();
myfile << sim_time << "\t" << x_com[0] << "\t" << x_com[1] << "\t" << x_com[2] << "\n";
myfile.close();
}
{
std::ofstream myfile("linear_momentum.txt", std::ios_base::app);
for (int i = 0; i < rsb->m_nFull; ++i)
{
total_linear += rsb->m_nodalMass[i] * rsb->m_nodes[i].m_v;
}
myfile << sim_time << "\t" << total_linear[0] << "\t" << total_linear[1] << "\t" << total_linear[2] << "\n";
myfile.close();
}
{
std::ofstream myfile("angular_momentum.txt", std::ios_base::app);
btVector3 ri(0, 0, 0);
for (int i = 0; i < rsb->m_nFull; ++i)
{
ri = rsb->m_nodes[i].m_x - x_com;
total_angular += rsb->m_nodalMass[i] * ri.cross(rsb->m_nodes[i].m_v);
}
myfile << sim_time << "\t" << total_angular[0] << "\t" << total_angular[1] << "\t" << total_angular[2] << "\n";
myfile.close();
}
}
void stepSimulation(float deltaTime)
{
// TODO: remove this. very hacky way of adding initial deformation
// btReducedSoftBody* rsb = static_cast<btReducedSoftBody*>(static_cast<btDeformableMultiBodyDynamicsWorld*>(m_dynamicsWorld)->getSoftBodyArray()[0]);
// if (first_step /* && !rsb->m_bUpdateRtCst*/)
// {
// getDeformedShape(rsb, 0, 1);
// first_step = false;
// // rsb->mapToReducedDofs();
// }
// btReducedSoftBody* rsb = static_cast<btReducedSoftBody*>(static_cast<btDeformableMultiBodyDynamicsWorld*>(m_dynamicsWorld)->getSoftBodyArray()[0]);
// if (first_step /* && !rsb->m_bUpdateRtCst*/)
// {
// getDeformedShape(rsb, 0, 1);
// first_step = false;
// // rsb->mapToReducedDofs();
// }
float internalTimeStep = 1. / 60.f;
// float internalTimeStep = 1e-3;
m_dynamicsWorld->stepSimulation(deltaTime, 1, internalTimeStep);
// sim_time += internalTimeStep;
// checkMomentum(rsb);
}
virtual void renderScene()