Why Use the Copy Texture Extension?

Why Use the Copy Texture Extension?

The copy texture extension lets you do multi-pass rendering, using the full set of OpenGL rendering capabilities to generate a texture you can use for further drawing. For example, you can render a scene, copy the resulting image to texture memory, and then apply the texture to a triangle mesh. By changing the mesh, you can warp the scene, break it into pieces, wrap it around complex objects, and so on.

Copying textures is also the only means of directly using video frames as textures, in conjunction with the video source extension. See "The Video Source Extension".