Bounce - Dealing With It

[Tonto]

I detect a collision between some object and another, and I get a normal to the surface where the collision occured, and the point of that collision. I try to sort of pretend that the velocity vector of the colliding object and the surface normal make like an 'angle of incidence'. And then I go farther and deal with that whole dealiothingy in put it into the context of a polar system sort of. Looks like this (multiplication operator does dot product):

        double incidence = std::acos( -v_ball.getNormalized() * normal );

        // Into polar (theta, radius) form
        double theta = std::acos( -v_ball.getNormalized() * CVector(1, 0) ) + incidence * 2;
        double radius = v_ball.length();

        // Into cartesian x, y form
        CVector out = CVector( std::cos( theta ) * radius, std::sin( theta ) * radius );
        m_ball.setVelocity( out );

So, basically my logic is like this. It's wrong I guess, because the ball goes all over the place unpredictably after the collision, but, it's my logic.

[VirtualAce]

Given you know the normal vector of the surface and the velocity vector of the ball -

Ball.VelocityVector*=Surface.Normal;

Given both are expressed as unit or normalized vectors.

[Tonto]

I ended up using the formula for vector reflection:

http://www.cse.iitb.ac.in/~adityagp/final/node3.html

( v_ball.getNormalized() - 2 * ( v_ball.getNormalized() * normal ) * normal ) * v_ball.length();

The multiplication operator denoting a dot product operation when operating on vectors there.

>> Ball.VelocityVector*=Surface.Normal;

What will that give me? It didn't seem to work in my program (even after scaling that vector)

[The Wazaa]

I'm not sure if this works, might be worth a try though:

Ball.vel = Ball.vel - 2 * absolute(normal) * ball.vel

Worked for me on normal = (-1, 0) and (0, 1), not sure if it's the general case though.

Good luck

Wazaa