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6.19 3D Textures

Three dimensional textures are a logical extension of 2D textures. In 3D textures, texels become unit cubes in texel space. They are packed into a rectangular parallelepiped, each dimension constrained to be a power of two. This texture map occupies a volume, rather than a rectangular region, and is accessed using three texture coordinates; $s$, $t$, and $r$. As with 2D textures, texture coordinates range from $0$ to $1$ in each dimension. Filtering is controlled in the same fashion as 2D textures, using texture parameters and texture environment.