Shaders and Texturing - An Introduction to Computer Graphics for Artists - page 199

Fig. 11.20 There are six major colors in this goose. Within each of these colors, most of the color
variation is due to lighting

11.5.4.2 Diffuse

The diffuse map represents the color of an object. Most apparent color variations in
objects are due to lighting rather than actual changes in the diffuse values of the
object itself. This means that most color maps can be much simpler than is obvious
(Fig. 11.20 ).
Variant colors within each of the major color divisions should be carefully
checked to ensure they are not the product of lighting, specularity, or other
effects, but are actual color changes within the material itself. Most objects will
not have many color changes within major color areas. To be generous, if they
each had fi ve variant colors, there would be a total of 35 colors needed for the
map before considering anti-aliasing. Anti-aliasing allows smooth blending
between colors. If fi ve colors are assigned for anti-aliasing to each of the 35 col-
ors identifi ed so far, the map will need only 175 colors, and this is generous.
Most of these colors will be calculated by the image editing application used. Of
the group, the seven major colors must be part of the palette. The four additional
colors per major color are optional, but should also be on the palette. With these
colors, the entire map can be painted.