Just spent half a day debugging this, so here it is for the future reference of the internets.

In a deferred rendering setup (see Game Angst for a good discussion of deferred shading & lighting), lights are applied using data from screen-space buffers. Position, normal and other things are reconstructed from buffers and lighting is computed “in screen space”.

Because each light is applied to a portion of the screen, the pixels it computes can belong to different objects. If in any place of lighting computation you use textures with mipmaps, be careful. Most common use for mipmapped light textures is light “cookies” (aka Gobo).

Let’s say we have a very simple scene with a spot light: (more…)

…I took a plane to Copenhagen. Oh, this sounds familiar…

Well ok, it all started a bit before: (more…)