Texture lights (also known as "
texlights") are
textures that emit light. They are often recommended over light
entities for general lighting as they suggest a more natural source of light than a point in space. Note, however, that this not necessarily true of
Source mapping, where they are generally discouraged.
Texture lighting is not a property inherent to certain textures, and thus any texture can be a texture light. There are a couple of ways of telling the
compile tools that you want a texture to act as a texture light. Firstly, texture lights can be defined in a file called
lights.rad and <mapname>.rad. Secondly, texture lights can be defined in an
info_texlights entity. Thirdly, and the best-in-class method, is to use VHLT's
light_surface.
Texture lights, by default, only emit a fixed light that cannot be turned on/off or have any special effects applied to them. However, these properties are possible to achieve. See
this tutorial for details. Or again, just use light_surface.