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add damping energy to mass spring

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This commit is contained in:
Xuchen Han
2019-09-18 16:06:09 -07:00
parent d761b2cd68
commit cca220eb27
5 changed files with 50 additions and 18 deletions
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10
examples/DeformableDemo/DeformableContact.cpp
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@@ -133,7 +133,7 @@ void DeformableContact::initPhysics()
btDefaultMotionState* myMotionState = new btDefaultMotionState(groundTransform); btDefaultMotionState* myMotionState = new btDefaultMotionState(groundTransform);
btRigidBody::btRigidBodyConstructionInfo rbInfo(mass, myMotionState, groundShape, localInertia); btRigidBody::btRigidBodyConstructionInfo rbInfo(mass, myMotionState, groundShape, localInertia);
btRigidBody* body = new btRigidBody(rbInfo); btRigidBody* body = new btRigidBody(rbInfo);
body->setFriction(1); body->setFriction(2);
//add the ground to the dynamics world //add the ground to the dynamics world
m_dynamicsWorld->addRigidBody(body); m_dynamicsWorld->addRigidBody(body);
@@ -156,12 +156,12 @@ void DeformableContact::initPhysics()
psb->setTotalMass(1); psb->setTotalMass(1);
psb->m_cfg.kKHR = 1; // collision hardness with kinematic objects psb->m_cfg.kKHR = 1; // collision hardness with kinematic objects
psb->m_cfg.kCHR = 1; // collision hardness with rigid body psb->m_cfg.kCHR = 1; // collision hardness with rigid body
psb->m_cfg.kDF = 2; psb->m_cfg.kDF = 1;
psb->m_cfg.collisions = btSoftBody::fCollision::SDF_RD; psb->m_cfg.collisions = btSoftBody::fCollision::SDF_RD;
psb->m_cfg.collisions |= btSoftBody::fCollision::VF_DD; psb->m_cfg.collisions |= btSoftBody::fCollision::VF_DD;
getDeformableDynamicsWorld()->addSoftBody(psb); getDeformableDynamicsWorld()->addSoftBody(psb);
btDeformableMassSpringForce* mass_spring = new btDeformableMassSpringForce(20,0.1, true); btDeformableMassSpringForce* mass_spring = new btDeformableMassSpringForce(10,1, true);
getDeformableDynamicsWorld()->addForce(psb, mass_spring); getDeformableDynamicsWorld()->addForce(psb, mass_spring);
m_forces.push_back(mass_spring); m_forces.push_back(mass_spring);
@@ -183,13 +183,13 @@ void DeformableContact::initPhysics()
psb2->setTotalMass(1); psb2->setTotalMass(1);
psb2->m_cfg.kKHR = 1; // collision hardness with kinematic objects psb2->m_cfg.kKHR = 1; // collision hardness with kinematic objects
psb2->m_cfg.kCHR = 1; // collision hardness with rigid body psb2->m_cfg.kCHR = 1; // collision hardness with rigid body
psb2->m_cfg.kDF = 2; psb2->m_cfg.kDF = 1;
psb2->m_cfg.collisions = btSoftBody::fCollision::SDF_RD; psb2->m_cfg.collisions = btSoftBody::fCollision::SDF_RD;
psb2->m_cfg.collisions |= btSoftBody::fCollision::VF_DD; psb2->m_cfg.collisions |= btSoftBody::fCollision::VF_DD;
psb->translate(btVector3(3,0,0)); psb->translate(btVector3(3,0,0));
getDeformableDynamicsWorld()->addSoftBody(psb2); getDeformableDynamicsWorld()->addSoftBody(psb2);
btDeformableMassSpringForce* mass_spring2 = new btDeformableMassSpringForce(20,0.1, true); btDeformableMassSpringForce* mass_spring2 = new btDeformableMassSpringForce(10,1, true);
getDeformableDynamicsWorld()->addForce(psb2, mass_spring2); getDeformableDynamicsWorld()->addForce(psb2, mass_spring2);
m_forces.push_back(mass_spring2); m_forces.push_back(mass_spring2);

2
examples/DeformableDemo/DeformableRigid.cpp
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@@ -238,7 +238,7 @@ void DeformableRigid::initPhysics()
psb->m_cfg.collisions = btSoftBody::fCollision::SDF_RD; psb->m_cfg.collisions = btSoftBody::fCollision::SDF_RD;
getDeformableDynamicsWorld()->addSoftBody(psb); getDeformableDynamicsWorld()->addSoftBody(psb);
btDeformableMassSpringForce* mass_spring = new btDeformableMassSpringForce(2,0.1, true); btDeformableMassSpringForce* mass_spring = new btDeformableMassSpringForce(30,1, true);
getDeformableDynamicsWorld()->addForce(psb, mass_spring); getDeformableDynamicsWorld()->addForce(psb, mass_spring);
m_forces.push_back(mass_spring); m_forces.push_back(mass_spring);

16
examples/DeformableDemo/GraspDeformable.cpp
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@@ -274,10 +274,10 @@ void GraspDeformable::initPhysics()
{ {
char relative_path[1024]; char relative_path[1024];
// b3FileUtils::findFile("banana.vtk", relative_path, 1024); // b3FileUtils::findFile("banana.vtk", relative_path, 1024);
b3FileUtils::findFile("ball.vtk", relative_path, 1024); // b3FileUtils::findFile("ball.vtk", relative_path, 1024);
// b3FileUtils::findFile("paper_collision.vtk", relative_path, 1024); // b3FileUtils::findFile("paper_collision.vtk", relative_path, 1024);
// b3FileUtils::findFile("single_tet.vtk", relative_path, 1024); // b3FileUtils::findFile("single_tet.vtk", relative_path, 1024);
// b3FileUtils::findFile("tube.vtk", relative_path, 1024); b3FileUtils::findFile("tube.vtk", relative_path, 1024);
// b3FileUtils::findFile("torus.vtk", relative_path, 1024); // b3FileUtils::findFile("torus.vtk", relative_path, 1024);
// b3FileUtils::findFile("paper_roll.vtk", relative_path, 1024); // b3FileUtils::findFile("paper_roll.vtk", relative_path, 1024);
// b3FileUtils::findFile("bread.vtk", relative_path, 1024); // b3FileUtils::findFile("bread.vtk", relative_path, 1024);
@@ -291,12 +291,12 @@ void GraspDeformable::initPhysics()
btSoftBody* psb = btSoftBodyHelpers::CreateFromVtkFile(getDeformableDynamicsWorld()->getWorldInfo(), relative_path); btSoftBody* psb = btSoftBodyHelpers::CreateFromVtkFile(getDeformableDynamicsWorld()->getWorldInfo(), relative_path);
// psb->scale(btVector3(30, 30, 30)); // for banana // psb->scale(btVector3(30, 30, 30)); // for banana
psb->scale(btVector3(.05, .05, .05)); // psb->scale(btVector3(.2, .2, .2));
// psb->scale(btVector3(2, 2, 2)); // psb->scale(btVector3(2, 2, 2));
// psb->scale(btVector3(.3, .3, .3)); // for tube, torus, boot psb->scale(btVector3(.3, .3, .3)); // for tube, torus, boot
// psb->scale(btVector3(1, 1, 1)); // for ditto // psb->scale(btVector3(.1, .1, .1)); // for ditto
psb->translate(btVector3(.25, 2, 0.4)); // psb->translate(btVector3(.25, 2, 0.4));
psb->getCollisionShape()->setMargin(0.02); psb->getCollisionShape()->setMargin(0.01);
psb->setTotalMass(.01); psb->setTotalMass(.01);
psb->m_cfg.kKHR = 1; // collision hardness with kinematic objects psb->m_cfg.kKHR = 1; // collision hardness with kinematic objects
psb->m_cfg.kCHR = 1; // collision hardness with rigid body psb->m_cfg.kCHR = 1; // collision hardness with rigid body
@@ -308,7 +308,7 @@ void GraspDeformable::initPhysics()
getDeformableDynamicsWorld()->addForce(psb, gravity_force); getDeformableDynamicsWorld()->addForce(psb, gravity_force);
m_forces.push_back(gravity_force); m_forces.push_back(gravity_force);
btDeformableNeoHookeanForce* neohookean = new btDeformableNeoHookeanForce(250,500); btDeformableNeoHookeanForce* neohookean = new btDeformableNeoHookeanForce(10,20, 0.01);
getDeformableDynamicsWorld()->addForce(psb, neohookean); getDeformableDynamicsWorld()->addForce(psb, neohookean);
m_forces.push_back(neohookean); m_forces.push_back(neohookean);
} }

2
src/BulletSoftBody/btDeformableBackwardEulerObjective.h
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@@ -93,6 +93,7 @@ public:
m_preconditioner->operator()(x,b); m_preconditioner->operator()(x,b);
} }
// reindex all the vertices
virtual void updateId() virtual void updateId()
{ {
size_t node_id = 0; size_t node_id = 0;
@@ -125,6 +126,7 @@ public:
m_implicit = implicit; m_implicit = implicit;
} }
// Calculate the total potential energy in the system
btScalar totalEnergy(btScalar dt); btScalar totalEnergy(btScalar dt);
}; };

38
src/BulletSoftBody/btDeformableMassSpringForce.h
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@@ -62,9 +62,9 @@ public:
btVector3 scaled_force = scale * m_dampingStiffness * v_diff; btVector3 scaled_force = scale * m_dampingStiffness * v_diff;
if (m_momentum_conserving) if (m_momentum_conserving)
{ {
if ((node2->m_q - node1->m_q).norm() > SIMD_EPSILON) if ((node2->m_x - node1->m_x).norm() > SIMD_EPSILON)
{ {
btVector3 dir = (node2->m_q - node1->m_q).normalized(); btVector3 dir = (node2->m_x - node1->m_x).normalized();
scaled_force = scale * m_dampingStiffness * v_diff.dot(dir) * dir; scaled_force = scale * m_dampingStiffness * v_diff.dot(dir) * dir;
} }
} }
@@ -118,9 +118,9 @@ public:
btVector3 local_scaled_df = scaled_k_damp * (dv[id2] - dv[id1]); btVector3 local_scaled_df = scaled_k_damp * (dv[id2] - dv[id1]);
if (m_momentum_conserving) if (m_momentum_conserving)
{ {
if ((node2->m_q - node1->m_q).norm() > SIMD_EPSILON) if ((node2->m_x - node1->m_x).norm() > SIMD_EPSILON)
{ {
btVector3 dir = (node2->m_q - node1->m_q).normalized(); btVector3 dir = (node2->m_x - node1->m_x).normalized();
local_scaled_df= scaled_k_damp * (dv[id2] - dv[id1]).dot(dir) * dir; local_scaled_df= scaled_k_damp * (dv[id2] - dv[id1]).dot(dir) * dir;
} }
} }
@@ -129,6 +129,7 @@ public:
} }
} }
} }
virtual double totalElasticEnergy(btScalar dt) virtual double totalElasticEnergy(btScalar dt)
{ {
double energy = 0; double energy = 0;
@@ -150,6 +151,35 @@ public:
return energy; return energy;
} }
virtual double totalDampingEnergy(btScalar dt)
{
double energy = 0;
int sz = 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)
{
sz = btMax(sz, psb->m_nodes[j].index);
}
}
TVStack dampingForce;
dampingForce.resize(sz+1);
for (int i = 0; i < dampingForce.size(); ++i)
dampingForce[i].setZero();
addScaledDampingForce(0.5, dampingForce);
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 btSoftBody::Node& node = psb->m_nodes[j];
energy -= dampingForce[node.index].dot(node.m_v) / dt;
}
}
return energy;
}
virtual void addScaledElasticForceDifferential(btScalar scale, const TVStack& dx, TVStack& df) virtual void addScaledElasticForceDifferential(btScalar scale, const TVStack& dx, TVStack& df)
{ {
// implicit damping force differential // implicit damping force differential