How to implement Megatextures

Question

I am interested in roughly how megatextures are/could be implemented on iOS.

In particular I am making a 2D platformer with a large (non-tiled) background and I would like to have one (precalculated, unreasonably large) image that is mapped to the background. One option I have gone with is to chop the precalulated image into tiles, and load/unload in the background.

I am however curious about megatextures. It would be far more convenient to map these all to one surface. Are megatextures simply another way of phrasing what I am doing right now, or is something more cunning going on. Is there one superlarge texture on the graphics card with multiple gltexsubimage2d calls going on?

Answer 1

Megatexture is a well-developed and advanced implementation of clip-mapping technique: http://en.wikipedia.org/wiki/Clipmap

So yes, basically it is a continuous background loading of content to be displayed and unloading of currently unused content.