You can even turn the lights on, that's quite neat

Are these static renders or full embedded 3D views? Looks great either way.

They're static. And in case you're wondering: The way it's done is you render an all-lights-off and an all-lights-on version. You use one version as the background and slice the other version up into separate rooms. Then show or hide those room images depending on the state of the lights in the room.

That would explain why the photons don't pass through open doorways! But in other cases, they do. I'm confused.