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6.1.3 Texture Coordinate Generation and Transformation

An alternative to assigning texture coordinate explicitly to every vertex is to have OpenGL generate texture coordinates for you. OpenGL's texture coordinate generation (often called texgen for short) can generate texture coordinates automatically as a linear function of the eye-space or object-space coordinates or using a special sphere map formula designed for environment mapping.

OpenGL also provides a 4 by 4 texture matrix that can be used to transform the per-vertex texture coordinates, whether supplied explicitly or implicitly through texture coordinate generation. The texture matrix provides a means to rescale, translate, or even project texture coordinates before the texture is applied during rasterization.