void pfxSetupSwingTwistJoint(
PfxJoint &joint,
const PfxRigidState &stateA,
const PfxRigidState &stateB,
PfxSolverBody &solverBodyA,
PfxSolverBody &solverBodyB,
PfxFloat timeStep
)
{
PfxVector3 rA = rotate(solverBodyA.m_orientation,joint.m_anchorA);
PfxVector3 rB = rotate(solverBodyB.m_orientation,joint.m_anchorB);
PfxVector3 vA = stateA.getLinearVelocity() + cross(stateA.getAngularVelocity(),rA);
PfxVector3 vB = stateB.getLinearVelocity() + cross(stateB.getAngularVelocity(),rB);
PfxVector3 vAB = vA-vB;
PfxVector3 angAB = stateA.getAngularVelocity() - stateB.getAngularVelocity();
PfxVector3 distance = (stateA.getPosition() + rA) - (stateB.getPosition() + rB);
PfxMatrix3 worldFrameA,worldFrameB;
worldFrameA = PfxMatrix3(solverBodyA.m_orientation) * joint.m_frameA;
worldFrameB = PfxMatrix3(solverBodyB.m_orientation) * joint.m_frameB;
// Linear Constraint
PfxMatrix3 K = PfxMatrix3::scale(PfxVector3(solverBodyA.m_massInv + solverBodyB.m_massInv)) -
crossMatrix(rA) * solverBodyA.m_inertiaInv * crossMatrix(rA) -
crossMatrix(rB) * solverBodyB.m_inertiaInv * crossMatrix(rB);
for(int c=0;c<3;c++) {
PfxJointConstraint &jointConstraint = joint.m_constraints[c];
PfxConstraintRow &constraint = jointConstraint.m_constraintRow;
PfxVector3 normal = worldFrameA[c];
PfxFloat posErr = dot(distance,-normal);
PfxFloat lowerLimit = -jointConstraint.m_maxImpulse;
PfxFloat upperLimit = jointConstraint.m_maxImpulse;
PfxFloat velocityAmp = 1.0f;
pfxCalcLinearLimit(jointConstraint,posErr,velocityAmp,lowerLimit,upperLimit);
PfxFloat denom = dot(K*normal,normal);
constraint.m_rhs = -velocityAmp*dot(vAB,normal);
constraint.m_rhs -= (jointConstraint.m_bias * (-posErr)) / timeStep;
constraint.m_rhs *= jointConstraint.m_weight/denom;
constraint.m_jacDiagInv = jointConstraint.m_weight*velocityAmp/denom;
constraint.m_lowerLimit = lowerLimit;
constraint.m_upperLimit = upperLimit;
pfxStoreVector3(normal,constraint.m_normal);
}
PfxVector3 axis[3];
PfxFloat angle[3];
pfxCalcJointAngleSwingTwist(worldFrameA,worldFrameB,angle,axis);
// Angular Constraint
for(int c=3;c<6;c++) {
PfxJointConstraint &jointConstraint = joint.m_constraints[c];
PfxConstraintRow &constraint = jointConstraint.m_constraintRow;
PfxVector3 normal = axis[c-3];
PfxFloat posErr = angle[c-3];
PfxFloat lowerLimit = -jointConstraint.m_maxImpulse;
PfxFloat upperLimit = jointConstraint.m_maxImpulse;
PfxFloat velocityAmp = 1.0f;
pfxCalcAngularLimit(jointConstraint,posErr,velocityAmp,lowerLimit,upperLimit);
PfxFloat denom = dot((solverBodyA.m_inertiaInv+solverBodyB.m_inertiaInv)*normal,normal);
constraint.m_rhs = -velocityAmp*dot(angAB,normal); // velocity error
constraint.m_rhs -= (jointConstraint.m_bias * (-posErr)) / timeStep; // position error
constraint.m_rhs *= jointConstraint.m_weight/denom;
constraint.m_jacDiagInv = jointConstraint.m_weight*velocityAmp/denom;
constraint.m_lowerLimit = lowerLimit;
constraint.m_upperLimit = upperLimit;
pfxStoreVector3(normal,constraint.m_normal);
}
}