Whether a particular pixel in the texture map is coloured as grass, rock, sand, or otherwise is determined by a map of land types called an attributes map1). Each land type has different affinities for water, steep/flat ground, etc, and these parameters are used in the land type assignment algorithm to calculate the attributes map. This same algorithm is also used for masking bump mapping in the light mapping algorithm, and for calculating per-pixel land types in the texture generation algorithm.
Land types are grouped together into climates so that, for example, a desert climate might have land types for sand, cliffs, oases, etc. Climates and their land types may be viewed/edited using the climate manager and climate editor windows.
Each climate has its own climate definition file (*.cli.xml).