Cube textures?

Cubic textures are used for environment mapping. The most common case of environment mapping is the reflections you see on the surface of an object.

For example, say your app has a really nice car in the middle of a showroom. By using an environment map, you can make the paint of the car look really glossy and reflect other objects in the room. The main reason cubic environment mapping is used is because it is very easy for hardware to perform the math necessary to make them work.

There is tons of info on this all over the web. A good google search should give you all you need.

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