Lightgrid

Revision as of 12:48, 24 July 2012

A three-dimensional data structure used to store static lighting on models. Lightgrid are created during LIGHT phase each time map is compiled.

How it works

Each cell of lightgrid stores this information:

• Ambient RGB
• Average light vector (used for diffuse lighting)
• Diffuse RGB

When rendered, entity sample it's position at lightgrid and get average ambient and diffuse components to be applied during shading. Any entity that doesnt use lightmaps and not fullbright is, by default, lit with lightgrid.

Resolution

Lightgrid resolution on a particular map comes from it's bounds and cell size.

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'.

IMPORTANT NOTE: Do not use too small cell size because amount on memory and time it takes to calculate grows geometrically.

Often map bounds is much bigger than the space players and NPC can walk in. 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.

Corrections

Sometimes lightgrid is lighter or darker that the rest of environments which makes entities to look out of the place.

In order to make lightgrid match environments, a corrections should be made in a map build script. There is two coefficients to mess with:

• diffuse scale: scales intensity of diffise lightgrid component
• ambient scale: scales ambient RGB component

Console variables

• r_ambient - adds intensity to lightmap and lightgrid. Positive values makes map brighter (note: does not work on some Blood Omnicide locations).
• r_fullbright - disables static lighting.

See also

• Lightmap