Trying to find a collision defelction angle

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?

So it’s not an “easy equation” but Xamarin’s game Fruity Falls supports circle vs. rotated polygon collision. Source is fully available here:

Thanks vchelaru, do you happen to know which module the calculation is in?

He’s an author of this game, so he should know :slightly_smiling:
The reflection functions are here