A bump texture allows you to create an illusion of surface relief (bumpiness). The bump texture does not alter the shape of the surfaces to which it is assigned. It is not a displacement mapping.
Bump textures must be normal maps (that is, they must contain elevation as well as vector information). You can create these types of images in Maya®, or use Adobe® Photoshop® plug-ins provided from the NVIDIA® SDK.
Click this check box to turn on bump for the material. Then, select a normal map to use as the bump map.
For more information on how to select and position image files, see Use image maps.