Notes

http://www.eisscholle.de/articles/gpu_asm_billboarding.pdf
http://www.cnblogs.com/AcerRail/archive/2008/03/04/1089639.html
http://developer.apple.com/documentation/GraphicsImaging/Conceptual/OpenGL-MacProgGuide/opengl_offscreen/chapter_5_section_5.html
http://developer.nvidia.com/forums/index.php?showtopic=1627
http://www.siggraph.org/publications/instructions/author-instructions.pdf
http://www.songho.ca/opengl/gl_fbo.html