Выдержка из оригинальной справки. (NDL Gamebryo 1.1)
The Bump Map is a special format map that represents the micro-scale bumpiness and glossiness of the surface being textured. The Bump map can be used with an environment map to create specular bump mapping or can be used alone to create diffuse bump mapping. There are two basic forms of specular Bump Maps: with and without Luminance (or Luma) channels. If present, the Luma channel represents the monochromatic glossiness of the surface. It is exactly equivalent to the Gloss Map above, but only allows attenuation of the environment map, not tinting.
The effect of the specular Bump Map itself is complex. An artist generates an RGB map (or RGBA if they wish to include a Luma channel) where the color channels (only red is used; green and blue are normally set equal to the red, forming a grayscale image) represent a height field — brighter means higher, darker means lower. The image converter converts this into the required format, and, when applied, the slope of the bumps in the bump map are used to shift the environment map on a per-pixel basis, making the surface appear to have subtle bumps in it. Depending on the overall "texture" of the Bump Map, the surface can be made to have any type of look — hammered metal, brushed aluminum, gritty stone, etc.
Note that the Bump Map is another optional effect — much but not all of existing 3D hardware will be able to support it. In cases where an Environment Map and a specular Bump Map are supplied but bump mapping is not supported, the object will appear to be completely smooth and mirror-reflective. Applications need to be prepared for such situations. Note also that if a bump map and a gloss map are both supplied, the hardware will use both if the appropriate level of multitexturing is supported. If the hardware cannot support all three textures in conjunction, the bump map will take priority over the gloss map on hardware that supports bump mapping.
Bump maps can also be used to create diffuse bump mapping effects. Because the implementation of diffuse bump mapping can vary from renderer to renderer, refer to the renderer documentation for more details about diffuse bump maps.
Because of the additional settings required by Bump Maps, the Bump Map slot in an NiTexturingProperty does not use the NiTexturingProperty::Map objects used by other static multitextures, but rather an NiTexturingProperty::BumpMap object, which includes the extra settings. This use of the BumpMap object is enforced by the interfaces.
