Rich_is_Bored's demonstration of how one can use complex projection images in ambient lights to achieve a light-mapping effect. ( Based on Lunaran's Quake 4 map "Strombine" which uses the same concept to amazing effect )
Rich_is_Bored:
![Doom 3 projection textures]()
A light shader is constructed with two images. A projection image and a falloff image. The projection image is what is projected. The falloff image specifies the intensity of the projection as it passes through the light volume.
The reason this works is because an ambient light is not directional and bleeds through walls illuminating all faces equally.
The trick, and it's not employed in the example I posted but it is used in the custom Quake 4 level Strombine, is that you can rotate the light and change the direction of projection.
So in cases where the geometry in a space runs in a common direction you can paint a custom light image to fake radiosity, soft shadows, or even consolidate lights into a single entity.
In theory it's also possible to break a room into several light volumes to accommodate geometry that doesn't run the length of a room. I haven't tried this yet and I imagine it gets complicated.
Wiki.thedarkmod.com
Based on Lunaran's Strombine map:
Lunaran.com
