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Code Issues Releases Wiki Activity

friction seems to be working. However, when the block is only sliding on the surface, there is no friction because no delta normal impulse...need to think

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This commit is contained in:
jingyuc 2021-08-25 00:38:29 -04:00
parent 166dc2865d
commit 52abe35e41
4 changed files with 60 additions and 54 deletions
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6
examples/ReducedDeformableDemo/FreeFall.cpp
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@ -163,7 +163,7 @@ void FreeFall::initPhysics()
// rsb->scale(btVector3(1, 1, 1));
rsb->translate(btVector3(0, 10, 0)); //TODO: add back translate and scale
// rsb->setTotalMass(0.5);
rsb->setStiffnessScale(1);
rsb->setStiffnessScale(10);
rsb->setDamping(damping_alpha, damping_beta);
// rsb->setFriction(200);
@ -189,13 +189,13 @@ void FreeFall::initPhysics()
// create a static rigid box as the ground
{
// btBoxShape* groundShape = createBoxShape(btVector3(btScalar(50), btScalar(50), btScalar(50)));
btBoxShape* groundShape = createBoxShape(btVector3(btScalar(5), btScalar(5), btScalar(5)));
btBoxShape* groundShape = createBoxShape(btVector3(btScalar(10), btScalar(10), btScalar(10)));
m_collisionShapes.push_back(groundShape);
btTransform groundTransform;
groundTransform.setIdentity();
groundTransform.setRotation(btQuaternion(btVector3(1, 0, 0), SIMD_PI / 6.0));
groundTransform.setOrigin(btVector3(0, -2, -2));
groundTransform.setOrigin(btVector3(0, -10, 2));
// groundTransform.setOrigin(btVector3(0, 0, 6));
// groundTransform.setOrigin(btVector3(0, -50, 0));
{

101
src/BulletSoftBody/BulletReducedSoftBody/btReducedDeformableContactConstraint.cpp
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@ -54,6 +54,9 @@ btReducedDeformableRigidContactConstraint::btReducedDeformableRigidContactConstr
m_impulseFactorNormal = 0;
m_impulseFactorTangent = 0;
m_rhs = 0;
m_cfm = 0;
m_erp = btScalar(0.2);
m_friction = btScalar(0.5);
m_contactNormalA = c.m_cti.m_normal;
m_contactNormalB = -c.m_cti.m_normal;
@ -63,58 +66,59 @@ btReducedDeformableRigidContactConstraint::btReducedDeformableRigidContactConstr
btScalar btReducedDeformableRigidContactConstraint::solveConstraint(const btContactSolverInfo& infoGlobal)
{
// const btSoftBody::sCti& cti = m_contact->m_cti;
btVector3 deltaVa = getVa() - m_bufferVelocityA;
btVector3 deltaVb = getDeltaVb();
std::cout << "deltaVa: " << deltaVa[0] << '\t' << deltaVa[1] << '\t' << deltaVa[2] << '\n';
std::cout << "deltaVb: " << deltaVb[0] << '\t' << deltaVb[1] << '\t' << deltaVb[2] << '\n';
// get relative velocity and magnitude
// get delta relative velocity and magnitude (i.e., how much impulse has been applied?)
btVector3 deltaV_rel = deltaVa - deltaVb;
btScalar deltaV_rel_normal = -btDot(deltaV_rel, m_contactNormalA);
// btVector3 v_rel = va - vb;
// btScalar v_rel_normal = -btDot(v_rel, m_contactNormalA);
// if (m_penetration > 0)
// {
// std::cout << "penetrate!!!!\n";
// v_rel_normal += m_penetration / infoGlobal.m_timeStep; // add penetration correction vel
// }
// get the normal impulse to be applied
btScalar deltaImpulse = m_rhs - deltaV_rel_normal / m_normalImpulseFactor;
// btScalar deltaImpulse = m_rhs - v_rel_normal * m_normalImpulseFactorInv;
// cumulative impulse that has been applied
btScalar sum = m_appliedNormalImpulse + deltaImpulse;
// if the cumulative impulse is pushing the object into the rigid body, set it zero
if (sum < 0)
{
std::cout <<"set zeroed!!!\n";
deltaImpulse = -m_appliedNormalImpulse;
m_appliedNormalImpulse = 0;
// cumulative impulse that has been applied
btScalar sum = m_appliedNormalImpulse + deltaImpulse;
// if the cumulative impulse is pushing the object into the rigid body, set it zero
if (sum < 0)
{
std::cout <<"set zeroed!!!\n";
deltaImpulse = -m_appliedNormalImpulse;
m_appliedNormalImpulse = 0;
}
else
{
m_appliedNormalImpulse = sum;
}
}
else
{
m_appliedNormalImpulse = sum;
}
std::cout << "m_appliedNormalImpulse: " << m_appliedNormalImpulse << '\n';
std::cout << "deltaImpulse: " << deltaImpulse << '\n';
// if (!infoGlobal.m_splitImpulse)
// {
// v_rel_normal += m_penetration * infoGlobal.m_deformable_erp / infoGlobal.m_timeStep;
// }
// if it's separating, no need to do anything
// if (v_rel_normal > 0)
// {
// return 0;
// }
// btScalar residualSquare = v_rel_normal * v_rel_normal; // get residual
// residual is the nodal normal velocity change in current iteration
btScalar residualSquare = deltaImpulse * m_normalImpulseFactor; // get residual
residualSquare *= residualSquare;
// // compute the tangential relative vel
// btVector3 v_rel_tangent = v_rel - v_rel_normal * cti.m_normal;
// use Coulomb friction (based on delta velocity, |dv_t| = |dv_n * friction|)
btScalar deltaImpulse_tangent = m_friction * deltaImpulse;
if (m_appliedNormalImpulse > 0)
{
btScalar sum = m_appliedTangentImpulse + deltaImpulse_tangent;
if (sum > m_appliedNormalImpulse * m_friction)
{
sum = m_appliedNormalImpulse * m_friction;
m_appliedTangentImpulse = sum;
}
else if (sum < - m_appliedNormalImpulse * m_friction)
{
sum = -m_appliedNormalImpulse * m_friction;
m_appliedTangentImpulse = sum;
}
deltaImpulse_tangent = sum - m_appliedTangentImpulse;
std::cout << "deltaImpulse_tangent: " << deltaImpulse_tangent << '\n';
}
// // friction correction
// btScalar delta_v_rel_normal = v_rel_normal;
@ -134,19 +138,14 @@ btScalar btReducedDeformableRigidContactConstraint::solveConstraint(const btCont
// std::cout << "friction called\n";
// }
// get total impulse
// btVector3 impulse_normal = m_impulseFactorInv * (-v_rel);
// btVector3 impulse_normal = m_contact->m_c0 * (cti.m_normal * (-v_rel_normal));
// btVector3 impulse = impulse_normal + impulse_tangent;
// btVector3 impulse = impulse_normal.dot(m_contactNormalA) * m_contactNormalA;
// get the total impulse vector
btVector3 impulse_normal = deltaImpulse * m_contactNormalA;
btVector3 impulse_tangent = -deltaImpulse_tangent * m_contactTangent;
btVector3 impulse = impulse_normal + impulse_tangent;
// btVector3 impulse = -m_normalImpulseFactorInv * v_rel_normal * m_contactNormalA;
// btVector3 impulse = m_appliedNormalImpulse * m_contactNormalA;
btVector3 impulse = deltaImpulse * m_contactNormalA;
btVector3 impulse_dir = impulse;
impulse_dir.safeNormalize();
std::cout << "impulse direct: " << impulse_dir[0] << '\t' << impulse_dir[1] << '\t' << impulse_dir[2] << '\n';
// btVector3 impulse_dir = impulse_tangent;
// impulse_dir.safeNormalize();
// std::cout << "impulse direct: " << impulse_dir[0] << '\t' << impulse_dir[1] << '\t' << impulse_dir[2] << '\n';
applyImpulse(impulse);
// applyImpulse(impulse); // TODO: apply impulse?
@ -204,9 +203,11 @@ void btReducedDeformableNodeRigidContactConstraint::warmStarting()
// we define the (+) direction of errors to be the outward surface normal of the rigid object
btVector3 v_rel = va - vb;
// get tangent direction
m_contactTangent = -(v_rel / v_rel.safeNorm() - m_contactNormalA);
btScalar velocity_error = -btDot(v_rel, m_contactNormalA); // magnitude of relative velocity
btScalar position_error = 0;
std::cout << "penetration = " << m_penetration << "\n";
if (m_penetration > 0)
{
// velocity_error += m_penetration / m_dt; // TODO: why?
@ -214,7 +215,7 @@ void btReducedDeformableNodeRigidContactConstraint::warmStarting()
else
{
// add penetration correction vel
position_error = m_penetration * btScalar(0.2) / m_dt;
position_error = m_penetration * m_erp / m_dt; //TODO: add erp parameter
}
// get the initial estimate of impulse magnitude to be applied
// m_rhs = -velocity_error * m_normalImpulseFactorInv;

5
src/BulletSoftBody/BulletReducedSoftBody/btReducedDeformableContactConstraint.h
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@ -40,9 +40,14 @@ class btReducedDeformableRigidContactConstraint : public btDeformableRigidContac
btScalar m_impulseFactorTangent;
btScalar m_normalImpulseFactor;
btScalar m_rhs;
btScalar m_cfm;
btScalar m_erp;
btScalar m_friction;
btVector3 m_contactNormalA; // for rigid body
btVector3 m_contactNormalB; // for reduced deformable body
btVector3 m_contactTangent; // tangential direction of the relative velocity
btVector3 m_relPosA; // relative position of the contact point for A
btVector3 m_relPosB; // relative position of the contact point for B
btMatrix3x3 m_impulseFactor; // total impulse matrix

2
src/BulletSoftBody/BulletReducedSoftBody/btReducedSoftBody.cpp
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@ -8,7 +8,7 @@
btReducedSoftBody::btReducedSoftBody(btSoftBodyWorldInfo* worldInfo, int node_count, const btVector3* x, const btScalar* m)
: btSoftBody(worldInfo, node_count, x, m)
{
m_rigidOnly = false; //! only use rigid frame to debug
m_rigidOnly = true; //! only use rigid frame to debug
// reduced deformable
m_reducedModel = true;