///bilateral constraint between two dynamic objects
///positive distance = separation, negative distance = penetration
public static void ResolveSingleBilateral(RigidBody body1, ref IndexedVector3 pos1,
RigidBody body2, ref IndexedVector3 pos2,
float distance, ref IndexedVector3 normal, ref float impulse, float timeStep)
{
float normalLenSqr = normal.LengthSquared();
Debug.Assert(Math.Abs(normalLenSqr) < 1.1f);
if (normalLenSqr > 1.1f)
{
impulse = 0f;
return;
}
IndexedVector3 rel_pos1 = pos1 - body1.GetCenterOfMassPosition();
IndexedVector3 rel_pos2 = pos2 - body2.GetCenterOfMassPosition();
//this jacobian entry could be re-used for all iterations
IndexedVector3 vel1 = body1.GetVelocityInLocalPoint(ref rel_pos1);
IndexedVector3 vel2 = body2.GetVelocityInLocalPoint(ref rel_pos2);
IndexedVector3 vel = vel1 - vel2;
IndexedBasisMatrix m1 = body1.GetCenterOfMassTransform()._basis.Transpose();
IndexedBasisMatrix m2 = body2.GetCenterOfMassTransform()._basis.Transpose();
JacobianEntry jac = new JacobianEntry(m1, m2, rel_pos1, rel_pos2, normal,
body1.GetInvInertiaDiagLocal(), body1.GetInvMass(),
body2.GetInvInertiaDiagLocal(), body2.GetInvMass());
float jacDiagAB = jac.GetDiagonal();
float jacDiagABInv = 1f / jacDiagAB;
float rel_vel = jac.GetRelativeVelocity(
body1.GetLinearVelocity(),
body1.GetCenterOfMassTransform()._basis.Transpose() * body1.GetAngularVelocity(),
body2.GetLinearVelocity(),
body2.GetCenterOfMassTransform()._basis.Transpose() * body2.GetAngularVelocity());
float a = jacDiagABInv;
rel_vel = normal.Dot(ref vel);
//todo: move this into proper structure
float contactDamping = 0.2f;
if (ONLY_USE_LINEAR_MASS)
{
float massTerm = 1f / (body1.GetInvMass() + body2.GetInvMass());
impulse = -contactDamping * rel_vel * massTerm;
}
else
{
float velocityImpulse = -contactDamping * rel_vel * jacDiagABInv;
impulse = velocityImpulse;
}
}
