Typically, bump mapping is implemented in custom rendering software on the host, as few hardware systems implement bump map evaluation directly. It may be possible to directly bump map an object covering a small number of pixels in software and composite the image into the non-bump-mapped scene using techniques discussed elsewhere in these notes, and retain interactive frame rates. However, the prohibitive cost of texture access and vector normalization make hardware assistance attractive.
The following sections present a technique for using texture maps to approximate bump mapping without requiring a custom renderer  . This multipass algorithm is an extension and refinement of texture embossing .