I immediately thought about Feynman talking about the "TREMENDOUS mess" bouncing around the room.
I can't even begin to imagine it.
This is computer-rendering light, not real light.
A careful watching of the first video can incidentally reveal why we don't simulate real light. Watch as the first clean pulse of light spreads out and goes from this really-easily-characterizable expanding circle to an ever-more-complicated set of waves as it moves out into the world. You can't afford to simulate things as waves, at least, not with conventional computers.
There's some other stuff regarding light's wave/particle duality, so I don't know if there's a simple solution to whether it propagates in all of these paths, or as a particle moving in a straight line.