I am currently interested in billiards and their trajectories. I would like to simulate a billiard inside a water tight mesh.

A mesh basically consists of a list of points in 3D space (vectors with 3 entries) together with a list of 3 vectors of natural numbers, which specify the corner points of each triangle. Now I would like to have a reflection whenever the trajectory of the ball crosses the triangle.

I would already be happy about pseudocode

So, technically the question is, how can I find a let the trajectory now it is crossing the triangle and it should perform a reflection.

Remark: I would later like to play billiards of charged balls in magnetic fields. I can therefore not assume that the balls follow a straight line.

Any ideas?