Methods and apparatus for 3-D image compositing. The compositing system can be used to render 3-D objects together to a scene, to combine together separately rendered 3-D objects in a scene including previously rendered objects, or to render some objects together while separately rendering and combining...http://www.google.de/patents/US7453459?utm_source=gb-gplus-sharePatent US7453459 - Composite rendering 3-D graphical objects
