Ray Tracing

Goddamn all of these homework threads. Let's talk about something interesting.

I'm starting work on a ray-tracer for shits, /proggles/ Any tips on speed improvements? It's being written in C.
I know the show stopper (usually) is having to check each element in the scene and see if it has been intersected by a casted ray. Any ideas on improvements in that area?

OP Here
>>7
Recommend a better rendering algorithm with as much realism as a two-pass raytracer that is faster then, and I'll look into that.

>>9
I'm a college kid, so my projects are made in my sparse spare time. After I make the well-designed one, I'll make a simple one and take you up on that.

Side note, it'd be interesting to make a ray tracing engine using pure Monte-Carlo simulation, having all rays traced from light sources and only gathering the ones that reach the camera. It would  be rather realistic, but fuck efficiency.