   Prefab z-buffers
  I recently had this idea of having a game world made up of tiles, with each tile consisting of both an rgb image and a z-buffer fragment. That way your visibility sorting can not go wrong and you can implement ''transparent'' pixels by giving them a real faraway z-coordinate. Furthermore you should be able to take advantage of graphics hardware with this.Has anyone here ever tried this or know of some project that uses it and if yes, did they run into any problems? I guess you''ll have to adjust the z-values of your tiles as they get further away, this might be a strain on the cpu if it can not be implemented to be done on the gpu somehow.Marijn 
The Sims did this, and it seemed to work well for getting pixel-perfect ordering. Theres several modding tools for it around that might be worth looking at. I think they did the whole thing in software, but if you''re planning on doing it on the GPU have a look into nailboards.. ;  The easiest way would be to do it all in software. To do it on the GPU, you would probably have to write your own pixel shader that reads a texel and uses it to modify the z-value of the pixel being written. If you are not planning on using the alpha channel of the textures, you could use that to store the z-value.   /Mattias Gustavssonwww.micogames.com