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/*
* Copyright (c) 2005 Erwin Coumans http://continuousphysics.com/Bullet/
*
* Permission to use, copy, modify, distribute and sell this software
* and its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies.
* Erwin Coumans makes no representations about the suitability
* of this software for any purpose.
* It is provided "as is" without express or implied warranty.
*/
#include "ContactConstraint.h"
#include "Dynamics/RigidBody.h"
#include "SimdVector3.h"
#include "JacobianEntry.h"
#include "ContactSolverInfo.h"
#include "GEN_MinMax.h"
#define ASSERT2 assert
//some values to find stable penalty method tresholds
float MAX_FRICTION = 100.f;
static SimdScalar ContactThreshold = -10.0f;
float useGlobalSettingContacts = false;//true;
SimdScalar contactDamping = 0.2f;
SimdScalar contactTau = .02f;//0.02f;//*0.02f;
SimdScalar restitutionCurve(SimdScalar rel_vel, SimdScalar restitution)
{
// return 0.f;
return restitution * GEN_min(1.0f, rel_vel / ContactThreshold);
}
SimdScalar calculateCombinedFriction(RigidBody& body0,RigidBody& body1)
{
SimdScalar friction = body0.getFriction() * body1.getFriction();
if (friction < 0.f)
friction = 0.f;
if (friction > MAX_FRICTION)
friction = MAX_FRICTION;
return friction;
}
//bilateral constraint between two dynamic objects
void resolveSingleBilateral(RigidBody& body1, const SimdVector3& pos1,
RigidBody& body2, const SimdVector3& pos2,
SimdScalar distance, const SimdVector3& normal,SimdScalar& impulse ,float timeStep)
{
float normalLenSqr = normal.length2();
ASSERT2(fabs(normalLenSqr) < 1.1f);
if (normalLenSqr > 1.1f)
{
impulse = 0.f;
return;
}
SimdVector3 rel_pos1 = pos1 - body1.getCenterOfMassPosition();
SimdVector3 rel_pos2 = pos2 - body2.getCenterOfMassPosition();
//this jacobian entry could be re-used for all iterations
SimdVector3 vel1 = body1.getVelocityInLocalPoint(rel_pos1);
SimdVector3 vel2 = body2.getVelocityInLocalPoint(rel_pos2);
SimdVector3 vel = vel1 - vel2;
JacobianEntry jac(body1.getCenterOfMassTransform().getBasis().transpose(),
body2.getCenterOfMassTransform().getBasis().transpose(),
rel_pos1,rel_pos2,normal,body1.getInvInertiaDiagLocal(),body1.getInvMass(),
body2.getInvInertiaDiagLocal(),body2.getInvMass());
SimdScalar jacDiagAB = jac.getDiagonal();
SimdScalar jacDiagABInv = 1.f / jacDiagAB;
SimdScalar rel_vel = jac.getRelativeVelocity(
body1.getLinearVelocity(),
body1.getCenterOfMassTransform().getBasis().transpose() * body1.getAngularVelocity(),
body2.getLinearVelocity(),
body2.getCenterOfMassTransform().getBasis().transpose() * body2.getAngularVelocity());
float a;
a=jacDiagABInv;
rel_vel = normal.dot(vel);
#ifdef ONLY_USE_LINEAR_MASS
SimdScalar massTerm = 1.f / (body1.getInvMass() + body2.getInvMass());
impulse = - contactDamping * rel_vel * massTerm;
#else
SimdScalar velocityImpulse = -contactDamping * rel_vel * jacDiagABInv;
impulse = velocityImpulse;
#endif
}
//velocity + friction
//response between two dynamic objects with friction
float resolveSingleCollisionWithFriction(
RigidBody& body1,
const SimdVector3& pos1,
RigidBody& body2,
const SimdVector3& pos2,
SimdScalar distance,
const SimdVector3& normal,
const ContactSolverInfo& solverInfo
)
{
float normalLenSqr = normal.length2();
ASSERT2(fabs(normalLenSqr) < 1.1f);
if (normalLenSqr > 1.1f)
return 0.f;
SimdVector3 rel_pos1 = pos1 - body1.getCenterOfMassPosition();
SimdVector3 rel_pos2 = pos2 - body2.getCenterOfMassPosition();
//this jacobian entry could be re-used for all iterations
JacobianEntry jac(body1.getCenterOfMassTransform().getBasis().transpose(),
body2.getCenterOfMassTransform().getBasis().transpose(),
rel_pos1,rel_pos2,normal,body1.getInvInertiaDiagLocal(),body1.getInvMass(),
body2.getInvInertiaDiagLocal(),body2.getInvMass());
SimdScalar jacDiagAB = jac.getDiagonal();
SimdScalar jacDiagABInv = 1.f / jacDiagAB;
SimdVector3 vel1 = body1.getVelocityInLocalPoint(rel_pos1);
SimdVector3 vel2 = body2.getVelocityInLocalPoint(rel_pos2);
SimdVector3 vel = vel1 - vel2;
SimdScalar rel_vel;
/* rel_vel = jac.getRelativeVelocity(
body1.getLinearVelocity(),
body1.getTransform().getBasis().transpose() * body1.getAngularVelocity(),
body2.getLinearVelocity(),
body2.getTransform().getBasis().transpose() * body2.getAngularVelocity());
*/
rel_vel = normal.dot(vel);
float combinedRestitution = body1.getRestitution() * body2.getRestitution();
SimdScalar restitution = restitutionCurve(rel_vel, combinedRestitution);
SimdScalar Kfps = 1.f / solverInfo.m_timeStep ;
float damping = solverInfo.m_damping ;
float Kerp = solverInfo.m_tau;
if (useGlobalSettingContacts)
{
damping = contactDamping;
Kerp = contactTau;
}
float Kcor = Kerp *Kfps;
SimdScalar positionalError = Kcor *-distance;
//jacDiagABInv;
SimdScalar velocityError = -(1.0f + restitution) * damping * rel_vel;
SimdScalar penetrationImpulse = positionalError * jacDiagABInv;
SimdScalar velocityImpulse = velocityError * jacDiagABInv;
SimdScalar friction_impulse = 0.f;
SimdScalar totalimpulse = penetrationImpulse+velocityImpulse;
if (totalimpulse > 0.f)
{
// SimdVector3 impulse_vector = normal * impulse;
body1.applyImpulse(normal*(velocityImpulse+penetrationImpulse), rel_pos1);
body2.applyImpulse(-normal*(velocityImpulse+penetrationImpulse), rel_pos2);
//friction
{
SimdVector3 vel1 = body1.getVelocityInLocalPoint(rel_pos1);
SimdVector3 vel2 = body2.getVelocityInLocalPoint(rel_pos2);
SimdVector3 vel = vel1 - vel2;
rel_vel = normal.dot(vel);
#define PER_CONTACT_FRICTION
#ifdef PER_CONTACT_FRICTION
SimdVector3 lat_vel = vel - normal * rel_vel;
SimdScalar lat_rel_vel = lat_vel.length();
float combinedFriction = calculateCombinedFriction(body1,body2);
if (lat_rel_vel > SIMD_EPSILON)
{
lat_vel /= lat_rel_vel;
SimdVector3 temp1 = body1.getInvInertiaTensorWorld() * rel_pos1.cross(lat_vel);
SimdVector3 temp2 = body2.getInvInertiaTensorWorld() * rel_pos2.cross(lat_vel);
friction_impulse = lat_rel_vel /
(body1.getInvMass() + body2.getInvMass() + lat_vel.dot(temp1.cross(rel_pos1) + temp2.cross(rel_pos2)));
SimdScalar normal_impulse = (penetrationImpulse+
velocityImpulse) * combinedFriction;
GEN_set_min(friction_impulse, normal_impulse);
body1.applyImpulse(lat_vel * -friction_impulse, rel_pos1);
body2.applyImpulse(lat_vel * friction_impulse, rel_pos2);
}
#endif
}
}
return velocityImpulse + friction_impulse;
}
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