Hi, I'm a PhD student working on Real Time Ray Tracing.
I actually reregistered to post this (I have a really old account I can't login to anymore tied to an old email address)
Anti aliasing in ray tracing is ridiculously simple. Yes, ray-tracing is a point-sampling algorithm and is therefore susceptible to jaggies, but you do NOT have to send out multiple rays per pixel.
After a frame is rendered with ONE primary ray per pixel, you then do a simple linear scan of the image. By comparing a pixel's values with neighbouring ones you can easily detect areas of the render where sharp transitions occur (jaggies etc). For those pixels and those pixels only, you can then send out one or more rays extra for anti-aliasing purposes.
Adaptive supersampling is fast and produces high quality results and it's been around since Whitted's initial work on recursive ray-tracing.
Other comments. "You must visit every object to build the data structure". Untrue. The data structures we use can be built on-demand as a ray traverses the scene. Also, O(N) or O(NlogN) rebuilds are not necessary between every frame. Simple O(logN) updates have been shown to work very well with deformable BVHs etc.
