I’ve been looking for a deflection/reflection equation without success. I completely understand the vector mirror approach, but I’m working in a rotating world where no collision is going happen on an axis. Just to make things a little more complicated, the collision is against a circle.

So, the circle is the solid with infinite mass, and being fired towards it are pixels. (For the sake of argument)

So at the point of collision I make a note of the vector for the projectile V1, and calculate a new vector from the collision point to the centre of the circle V2. Now if I work out the angle of V2, +90 or -90 degrees I have a plane to bounce off, but now I’m working in vectors and angles and I’m getting confused trying to work out if I need to be working in quadrants, or rotating everything, or should I just be rotating vectors.

Is there an easy equation?