My colleague told me this realtime raytracing demo with photon mapping (caustics). My machine has not enough power to run the demo. But it is quite impressive that just 4k bytes demo program can do this in realtime. Unfortunately, the code is not published.
The rendering time in a movie sometimes took 8 hours to render a frame. Which means it takes more than 8 days for one second movie. But these people usually has a render farm that contains 1000 or more computers. So, after they start render images, 1000 frames will be ready. For this demo we can take video directory. When you visit to YouTube, there are higher quality movie.
19 hours ago