Ray marching

Drag the gold origin and the small ring to give the ray a new start and direction. Each step is exactly as long as the distance from that point to the nearest surface, so the circle around every step is empty. Head-on, the ray arrives in a few steps; grazing past an edge, its steps shrink and the count shoots up. The corner plots the distance along the ray and every step; choose Fan (21 rays) to send a fan of rays from the same origin.