Выдержка из оригинальной справки. (NDL Gamebryo 1.1)
Detail maps are r,g,b maps that define high-frequency detail to be overlaid on a base texture. The map will only need an alpha channel if being used on the PS2 (and only then if you're not using the RGB 3-pass checkbox). An example of the need for detail maps is often seen in so-called "First-person shooter" games, when the player walks up very close to a wall while facing it. With just a base texture, most applications cannot afford infinite detail in the map (since that would require huge textures), so the filtering produces a blurred, soft image. This result is jarring to players who had been drawn into believing in the otherwise detailed game world. Detail maps can alleviate this problem by using an important observation: when the camera is close enough to a surface that it looks blurry, they can only see a small part of the base texture at a time. Because of this behavior the detail map should be a highly repeated noise pattern. The "Detail" map field is intended to hold the texture that will provide fine grain detail for the base map.
As with dark maps, the color of the base texture and the color of the detail map are multiplied together. Unlike dark maps, the result is multiplied by two. The detail map may thus darken or brighten the base texture. A pure white value will double the brightness of the base map while a pure black value will still make the base map's pixel become black. You should usually create a detail map so that its average color is 128,128,128, leaving the base map unchanged. In this way, when the object is viewed at a distance, it will appear the same with or without the detail texture.
In some ways, it is similar to the effect of a dark map, using two small textures to create the appearance of one very large texture. In fact, these techniques can be used together (easily affordable on reasonably powerful hardware—check your application requirements), to create textures that appear to be enormous. For example, a 64x64 detail texture repeated 32 times over a base texture that is itself repeated 16 times over a dark map gives an overall texturing effect that appears to be 64 times 32 times 16—effectively, what appears to be a 32,768x32,768-pixel texture.
