I've been wondering if I should put pairs of visportals on some of my windowpanes in my map, like in Komag's tutorial video, but just about the only thing about visportals I don't get is what's the actual difference, performance-wise, between a closed and an open visportal in a situation where there's next to nothing being rendered in the open visleaf anyway, like in the picture. Or is it that the entire visleaf is rendered anyway but r_showtris will only show tris that the player can "see" in there through that visportal, hence the need for pairs of them in certain situations? And another thing I've been meaning to ask, I've thought of using a number of small ambient lights to simulate radiosity/light bounce paired with a principal, shadowcasting pointlight in order to avoid the light bleed of one big ambient light while still being able to change the ambients' color independent of the pointlight. You can see how it's set up, 3rd light from left to right is the principal one, and the other three are biground ambient lights that overlap for better color blending. Now the thing is, I know lightpasses on surfaces are the engine's biggest FPS eater. But is it so bad if it's just small ambients rather than shadowcasting pointlights? I know, I know, this is an extremely lazy method to do this sorta thing and I would be much better off creating a custom light falloff texture (and I probably will later), but I'm wondering for the sake of science.