Right, "complex scenes" are never completely static; spaces and textures changes if you move around. I find that particularly interesting because I can perceive and remember details (for instance the pattern of a mosaic), but whenever you check again, it change, so it seems like the buffer were this images are coming from is separated from the region of my brain in charge of remembering my current dream.

Written text is non-persistent too. If you're dreaming and look away and back at a sign, newspaper, whatever, the words all change.

I've used the light switch thing to trigger a number of lucid dreams too, I always assumed that your brain just doesn't bother wiring things like that up, rather than the complexity of shading being an issue.