Bump Maps

From ZBrush Info

Bump Maps

Bump mapping is a technique that allows a flat polygon to presented as if it had more geometric detail. This is accomplished by applying a grayscale texture map to the polygon. The intensity of a mapped pixel is interpreted as a height above the polygon, up to a certain maximum. For example, a pure white pixel might indicate the surface of the polygon, a pure black pixel might be used to specify a height of 1/10" above the surface of the polygon, and so a 50% gray pixel would mean 1/20" above the polygon. For various reasons, 8-bit grayscale images are usually used for bump maps. Bump maps provide far more realism than simple textures which have been just been painted to appear bumpy, since the bump map will correctly reflect light sources from any angle, while the simple texture map always appears to be lit from one angle.

Bump maps give the appearance of features on a surface, but the geometry of the surface is not changed. This is apparent when a bump-mapped polygon is viewed from the side. Even though the bump map might cause the polygon to appear to have quite pronounced surface bumps or grooves when viewed head-on, the profile of the polygon viewed from the side will be completely flat. In addition, bump maps do not generate shadows. For these reasons, bump maps are best used to provide detail that is already very flat, such as the dimples in an orange.

To Learn About Painting Bump Maps Click Here.