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Code Issues Releases Wiki Activity

separate in-plane and bending stiffness for mass spring model for easier parameter tuning

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This commit is contained in:
Xuchen Han 2019-11-27 11:40:10 -08:00
parent 574343405d
commit 7bce5d61f4
6 changed files with 50 additions and 35 deletions
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5
examples/SharedMemory/PhysicsClientC_API.cpp
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@ -422,11 +422,12 @@ B3_SHARED_API int b3LoadSoftBodySetFrictionCoefficient(b3SharedMemoryCommandHand
return 0;
}
B3_SHARED_API int b3LoadSoftBodyUseBendingSprings(b3SharedMemoryCommandHandle commandHandle, int useBendingSprings)
B3_SHARED_API int b3LoadSoftBodyUseBendingSprings(b3SharedMemoryCommandHandle commandHandle, int useBendingSprings, double bendingStiffness)
{
struct SharedMemoryCommand* command = (struct SharedMemoryCommand*)commandHandle;
b3Assert(command->m_type == CMD_LOAD_SOFT_BODY);
command->m_loadSoftBodyArguments.m_useBendingSprings = useBendingSprings;
command->m_loadSoftBodyArguments.m_useBendingSprings = useBendingSprings;
command->m_loadSoftBodyArguments.m_springBendingStiffness = bendingStiffness;
command->m_updateFlags |= LOAD_SOFT_BODY_ADD_BENDING_SPRINGS;
return 0;
}

2
examples/SharedMemory/PhysicsClientC_API.h
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@ -643,7 +643,7 @@ extern "C"
B3_SHARED_API int b3LoadSoftBodyUseSelfCollision(b3SharedMemoryCommandHandle commandHandle, int useSelfCollision);
B3_SHARED_API int b3LoadSoftBodyUseFaceContact(b3SharedMemoryCommandHandle commandHandle, int useFaceContact);
B3_SHARED_API int b3LoadSoftBodySetFrictionCoefficient(b3SharedMemoryCommandHandle commandHandle, double frictionCoefficient);
B3_SHARED_API int b3LoadSoftBodyUseBendingSprings(b3SharedMemoryCommandHandle commandHandle, int useBendingSprings);
B3_SHARED_API int b3LoadSoftBodyUseBendingSprings(b3SharedMemoryCommandHandle commandHandle, int useBendingSprings, double bendingStiffness);
B3_SHARED_API b3SharedMemoryCommandHandle b3InitCreateSoftBodyAnchorConstraintCommand(b3PhysicsClientHandle physClient, int softBodyUniqueId, int nodeIndex, int bodyUniqueId, int linkIndex, const double bodyFramePosition[3]);

33
examples/SharedMemory/PhysicsServerCommandProcessor.cpp
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@ -8070,7 +8070,7 @@ bool PhysicsServerCommandProcessor::processLoadSoftBodyCommand(const struct Shar
{
collisionMargin = clientCmd.m_loadSoftBodyArguments.m_collisionMargin;
}
btScalar spring_bending_stiffness = 0;
{
btSoftBody* psb = NULL;
@ -8137,7 +8137,7 @@ bool PhysicsServerCommandProcessor::processLoadSoftBodyCommand(const struct Shar
}
}
#ifndef SKIP_DEFORMABLE_BODY
btScalar spring_elastic_stiffness, spring_damping_stiffness;
btScalar spring_elastic_stiffness, spring_damping_stiffness;
if (clientCmd.m_updateFlags & LOAD_SOFT_BODY_ADD_MASS_SPRING_FORCE)
{
btDeformableMultiBodyDynamicsWorld* deformWorld = getDeformableWorld();
@ -8145,7 +8145,11 @@ bool PhysicsServerCommandProcessor::processLoadSoftBodyCommand(const struct Shar
{
spring_elastic_stiffness = clientCmd.m_loadSoftBodyArguments.m_springElasticStiffness;
spring_damping_stiffness = clientCmd.m_loadSoftBodyArguments.m_springDampingStiffness;
btDeformableLagrangianForce* springForce = new btDeformableMassSpringForce(spring_elastic_stiffness, spring_damping_stiffness, false);
if (clientCmd.m_updateFlags & LOAD_SOFT_BODY_ADD_BENDING_SPRINGS)
{
spring_bending_stiffness = clientCmd.m_loadSoftBodyArguments.m_springBendingStiffness;
}
btDeformableLagrangianForce* springForce = new btDeformableMassSpringForce(spring_elastic_stiffness, spring_damping_stiffness, false, spring_bending_stiffness);
deformWorld->addForce(psb, springForce);
m_data->m_lf.push_back(springForce);
}
@ -8178,12 +8182,16 @@ bool PhysicsServerCommandProcessor::processLoadSoftBodyCommand(const struct Shar
deformWorld->addForce(psb, neohookeanForce);
m_data->m_lf.push_back(neohookeanForce);
}
btScalar spring_elastic_stiffness, spring_damping_stiffness;
btScalar spring_elastic_stiffness, spring_damping_stiffness;
if (clientCmd.m_updateFlags & LOAD_SOFT_BODY_ADD_MASS_SPRING_FORCE)
{
spring_elastic_stiffness = clientCmd.m_loadSoftBodyArguments.m_springElasticStiffness;
spring_damping_stiffness = clientCmd.m_loadSoftBodyArguments.m_springDampingStiffness;
btDeformableLagrangianForce* springForce = new btDeformableMassSpringForce(spring_elastic_stiffness, spring_damping_stiffness, true);
if (clientCmd.m_updateFlags & LOAD_SOFT_BODY_ADD_BENDING_SPRINGS)
{
spring_bending_stiffness = clientCmd.m_loadSoftBodyArguments.m_springBendingStiffness;
}
btDeformableLagrangianForce* springForce = new btDeformableMassSpringForce(spring_elastic_stiffness, spring_damping_stiffness, true, spring_bending_stiffness);
deformWorld->addForce(psb, springForce);
m_data->m_lf.push_back(springForce);
}
@ -8258,19 +8266,18 @@ bool PhysicsServerCommandProcessor::processLoadSoftBodyCommand(const struct Shar
friction_coeff = loadSoftBodyArgs.m_frictionCoeff;
}
psb->m_cfg.kDF = friction_coeff;
bool use_bending_spring = true;
bool use_bending_spring = false;
if (clientCmd.m_updateFlags & LOAD_SOFT_BODY_ADD_BENDING_SPRINGS)
{
use_bending_spring = loadSoftBodyArgs.m_useBendingSprings;
use_bending_spring = loadSoftBodyArgs.m_useBendingSprings;
if (use_bending_spring)
{
psb->generateBendingConstraints(2);
}
}
btSoftBody::Material* pm = psb->appendMaterial();
pm->m_flags -= btSoftBody::fMaterial::DebugDraw;
if (use_bending_spring)
{
psb->generateBendingConstraints(2,pm);
}
// turn on the collision flag for deformable
// collision between deformable and rigid
psb->m_cfg.collisions = btSoftBody::fCollision::SDF_RD;

25
examples/SharedMemory/SharedMemoryCommands.h
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@ -523,18 +523,19 @@ struct LoadSoftBodyArgs
double m_mass;
double m_collisionMargin;
double m_initialPosition[3];
double m_initialOrientation[4];
double m_springElasticStiffness;
double m_springDampingStiffness;
double m_corotatedMu;
double m_corotatedLambda;
int m_useBendingSprings;
double m_collisionHardness;
double m_useSelfCollision;
double m_frictionCoeff;
double m_NeoHookeanMu;
double m_NeoHookeanLambda;
double m_NeoHookeanDamping;
double m_initialOrientation[4];
double m_springElasticStiffness;
double m_springDampingStiffness;
double m_springBendingStiffness;
double m_corotatedMu;
double m_corotatedLambda;
int m_useBendingSprings;
double m_collisionHardness;
double m_useSelfCollision;
double m_frictionCoeff;
double m_NeoHookeanMu;
double m_NeoHookeanLambda;
double m_NeoHookeanDamping;
int m_useFaceContact;
char m_simFileName[MAX_FILENAME_LENGTH];
};

7
examples/pybullet/pybullet.c
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@ -1973,7 +1973,7 @@ static PyObject* pybullet_loadSoftBody(PyObject* self, PyObject* args, PyObject*
int physicsClientId = 0;
int flags = 0;
static char* kwlist[] = {"fileName", "basePosition", "baseOrientation", "scale", "mass", "collisionMargin", "physicsClientId", "useMassSpring", "useBendingSprings", "useNeoHookean", "springElasticStiffness", "springDampingStiffness", "NeoHookeanMu", "NeoHookeanLambda", "NeoHookeanDamping", "frictionCoeff", "useFaceContact", "useSelfCollision", NULL};
static char* kwlist[] = {"fileName", "basePosition", "baseOrientation", "scale", "mass", "collisionMargin", "physicsClientId", "useMassSpring", "useBendingSprings", "useNeoHookean", "springElasticStiffness", "springDampingStiffness", "springBendingStiffness", "NeoHookeanMu", "NeoHookeanLambda", "NeoHookeanDamping", "frictionCoeff", "useFaceContact", "useSelfCollision", NULL};
int bodyUniqueId = -1;
const char* fileName = "";
@ -1985,6 +1985,7 @@ static PyObject* pybullet_loadSoftBody(PyObject* self, PyObject* args, PyObject*
int useNeoHookean = 0;
double springElasticStiffness = 1;
double springDampingStiffness = 0.1;
double springBendingStiffness = 0.1;
double NeoHookeanMu = 1;
double NeoHookeanLambda = 1;
double NeoHookeanDamping = 0.1;
@ -2002,7 +2003,7 @@ static PyObject* pybullet_loadSoftBody(PyObject* self, PyObject* args, PyObject*
PyObject* basePosObj = 0;
PyObject* baseOrnObj = 0;
if (!PyArg_ParseTupleAndKeywords(args, keywds, "s|OOdddiiiiddddddii", kwlist, &fileName, &basePosObj, &baseOrnObj, &scale, &mass, &collisionMargin, &physicsClientId, &useMassSpring, &useBendingSprings, &useNeoHookean, &springElasticStiffness, &springDampingStiffness, &NeoHookeanMu, &NeoHookeanLambda, &NeoHookeanDamping, &frictionCoeff, &useFaceContact, &useSelfCollision))
if (!PyArg_ParseTupleAndKeywords(args, keywds, "s|OOdddiiiidddddddii", kwlist, &fileName, &basePosObj, &baseOrnObj, &scale, &mass, &collisionMargin, &physicsClientId, &useMassSpring, &useBendingSprings, &useNeoHookean, &springElasticStiffness, &springDampingStiffness, &springBendingStiffness, &NeoHookeanMu, &NeoHookeanLambda, &NeoHookeanDamping, &frictionCoeff, &useFaceContact, &useSelfCollision))
{
return NULL;
}
@ -2058,7 +2059,7 @@ static PyObject* pybullet_loadSoftBody(PyObject* self, PyObject* args, PyObject*
if (useMassSpring)
{
b3LoadSoftBodyAddMassSpringForce(command, springElasticStiffness, springDampingStiffness);
b3LoadSoftBodyUseBendingSprings(command, useBendingSprings);
b3LoadSoftBodyUseBendingSprings(command, useBendingSprings, springBendingStiffness);
}
if (useNeoHookean)
{

13
src/BulletSoftBody/btDeformableMassSpringForce.h
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@ -23,14 +23,18 @@ class btDeformableMassSpringForce : public btDeformableLagrangianForce
// If true, the damping force will be in the direction of the spring
// If false, the damping force will be in the direction of the velocity
bool m_momentum_conserving;
btScalar m_elasticStiffness, m_dampingStiffness;
btScalar m_elasticStiffness, m_dampingStiffness, m_bendingStiffness;
public:
typedef btAlignedObjectArray<btVector3> TVStack;
btDeformableMassSpringForce() : m_momentum_conserving(false), m_elasticStiffness(1), m_dampingStiffness(0.05)
{
}
btDeformableMassSpringForce(btScalar k, btScalar d, bool conserve_angular = true) : m_momentum_conserving(conserve_angular), m_elasticStiffness(k), m_dampingStiffness(d)
btDeformableMassSpringForce(btScalar k, btScalar d, bool conserve_angular = true, double bending_k = -1) : m_momentum_conserving(conserve_angular), m_elasticStiffness(k), m_dampingStiffness(d), m_bendingStiffness(bending_k)
{
if (m_bendingStiffness < btScalar(0))
{
m_bendingStiffness = m_elasticStiffness;
}
}
virtual void addScaledForces(btScalar scale, TVStack& force)
@ -103,7 +107,8 @@ public:
// elastic force
btVector3 dir = (node2->m_q - node1->m_q);
btVector3 dir_normalized = (dir.norm() > SIMD_EPSILON) ? dir.normalized() : btVector3(0,0,0);
btVector3 scaled_force = scale * m_elasticStiffness * (dir - dir_normalized * r);
btScalar scaled_stiffness = scale * (link.m_bbending ? m_bendingStiffness : m_elasticStiffness);
btVector3 scaled_force = scaled_stiffness * (dir - dir_normalized * r);
force[id1] += scaled_force;
force[id2] -= scaled_force;
}
@ -212,7 +217,6 @@ public:
{
continue;
}
btScalar scaled_k = m_elasticStiffness * scale;
for (int j = 0; j < psb->m_links.size(); ++j)
{
const btSoftBody::Link& link = psb->m_links[j];
@ -227,6 +231,7 @@ public:
btVector3 dir_normalized = (dir_norm > SIMD_EPSILON) ? dir.normalized() : btVector3(0,0,0);
btVector3 dx_diff = dx[id1] - dx[id2];
btVector3 scaled_df = btVector3(0,0,0);
btScalar scaled_k = scale * (link.m_bbending ? m_bendingStiffness : m_elasticStiffness);
if (dir_norm > SIMD_EPSILON)
{
scaled_df -= scaled_k * dir_normalized.dot(dx_diff) * dir_normalized;