// TBD: too much passing around of the Physics object. Probably better if
// it was static. there is no way to individually set the kfr and friction of the
// surfaces since they are calculated here from properties of the Physics
// object. Also, review for too much object creation
public virtual Vector ResolveCollision( Vector normal, Engine engine)
{
// get the velocity
Vector vel = curr.MinusNew( prev );
double sDotV = normal.Dot( vel );
// compute momentum of particle perpendicular to normal
Vector velProjection = vel.MinusNew( normal.MultNew( sDotV ) );
Vector perpMomentum = velProjection.MultNew( engine.CoeffFric );
// compute momentum of particle in direction of normal
Vector normMomentum = normal.MultNew( sDotV * engine.CoeffRest );
Vector totalMomentum = normMomentum.PlusNew( perpMomentum );
// set new velocity w/ total momentum
Vector newVel = vel.MinusNew( totalMomentum );
// project out of collision
curr.Plus( mtd );
// apply new velocity
prev = curr.MinusNew( newVel );
return newVel;
}
private double CalcTheta( Vector pa, Vector pb, Vector pc )
{
Vector AB = new Vector( pb.X - pa.X, pb.Y - pa.Y );
Vector BC = new Vector( pc.X - pb.X, pc.Y - pb.Y );
double dotProd = AB.Dot( BC );
double crossProd = AB.Cross( BC );
return Math.Atan2( crossProd, dotProd );
}