Textured Lights
Textures can also be used to add visual richness to light sources and allow for complex intensity distribution or spotlight functions. For lights that have all their illumination limited to a cone or frustum, projective textures can be used to modulate the light intensity.
Projective Textures
For lights that are not limited to a frustum but illuminate in all directions, a cube map can be used to modulate the intensity, instead of a two-dimensional projective texture. One-dimensional textures can be used to define arbitrary distance falloff functions. Combined with a two-dimensional angular attenuation map, this can allow for complex volumetric lighting patterns. A more general possibility is to use three-dimensional (volume) textures to control the light’s falloff. This allows for arbitrary volumes of effect, including light beams. This technique is memory intensive (as are all volume textures). If the light’s volume of effect is symmetrical along the three axes, the memory footprint can be reduced eightfold by mirroring the data into each octant.
Textures can be added to any light type to enable additional visual effects. Textured lights allow for easy control of the illumination by artists, who can simply edit the texture used.