OpenGL Utility Library
The OpenGL Utility Library (GLU) is a computer graphics library for OpenGL. It consists of a number of functions that use the base OpenGL library to provide higher-level drawing routines from the more primitive routines that OpenGL provides. It is usually distributed with the base OpenGL package. GLU is not implemented in the embedded version of the OpenGL package, OpenGL ES. Among these features are mapping between screen- and world-coordinates, generation of texture mipmaps, drawing of quadric surfaces, NURBS, tessellation of polygonal primitives, interpretation of OpenGL error codes, an extended range of transformation routines for  setting up viewing volumes and simple positioning of the camera, generally in more human-friendly terms than the routines presented by OpenGL. It also provides additional primitives for use in OpenGL applications, including spheres, cylinders and disks. All GLU functions start with the codice_1 prefix. An example function is codice_2 which defines a two dimensional orthographic projection matrix. The GLU specification was last updated in 1998, and it depends on features which were deprecated with the release of OpenGL 3.1 in 2009. Specifications for GLU are still available here