The pixel texture extension (SGIX_pixel_texture) allows multi-dimensional lookups through OpenGL's texturing capability. Remember that OpenGL defines rasterization of a pixel image during a glDrawPixels() or glCopyPixels() command as the generation of a fragment for each pixel in the image. Per-fragment operations are applied, including texturing (if enabled). If the input image contained color data, each fragment's color comes from the color of the pixel that generated it. The texture coordinate of the fragment is taken from the current raster position, which is generally not useful because the texture coordinate will be constant over the pixel rectangle. The pixel texture extension allows the texture coordinates , , , and of the fragment to be copied from the color coordinates R, G, B, and A of the pixel. With three and four dimensional textures (EXT_texture3D and SGIS_texture4D), arbitrary effects can be implemented (although the texture storage requirements to do so can be staggering).
The pixel texture extension is supported by the following vendors:
Pixel texture is not part of the imaging subset of OpenGL 1.2.