[beagle3]

They aren't.....

Some popular shortcuts include:

- Cut at n hops (with n=4 or n=8 popular choices), defaulting to "ambient" light after that

- Give each material an "ambient" color, so that you don't actually need to trace every pixel back into every light source (just into e.g. spotlights)

- Solve a radiosity equation for the surface colors, and trace rays for textures/reflections.

Complete ray tracing is, indeed, insane - in fact, to get high quality pictures and avoid aliasing, most ray tracers send multiple rays through every picture and average the result.

[beagle3]

(too late to edit:) that was supposed to be "multiple rays through every pixel "