Lightgrid
Lightgrid or volumeric lighting - a data structure used to store static lighting for models. Lightgrid are created during LIGHT phase each time map is compiled.
How it works
Each cell of lightgrid stores this information:
- Ambient light RGB
- Diffuse light RGB
- Light vector
When rendered, entity sample it's position at lightgrid and find average ambient and diffuse lighting to be applied during shading.
Level Design Notes
Default lightgrid cell size in game units is '64 64 128'. It can be customized with "gridsize" worldspawn key. Most of Blood Omnicide maps using lightgrid size '32 32 32' or '32 32 64'.
Often map bounds is much bigger than the space players and NPC can walk on. To not waste memory and reduce map compile time, level designer should place a brush covered by common/lightgrid material. That brush will set the area where lightgrid will be calculated and applied.
Sometimes lightgrid is more bright or darker that the rest of environments, this makes entities to look out of the place. In order to make lightgrid match environments corrections should be made in a map build script. There is 2 coefficients to fix lightgrid: diffuse scale (scales intensity of diffise lightgrid component) and ambient scale (scales ambient RGB component).
