View Full Version : accessing frame buffer

03-31-2004, 02:23 AM
I did not seen any built in variable to access currently rendered pixel color and depth - I mean not the currently processed pixel but already processed pixel, available in the frame buffer (in case of a multipasse rendering).
What I'm talking about would be a kind of gl_FragColor or gl_FragDepth but giving current frame buffer color and depth for the current pixel processed. Do you know how to access it ?

03-31-2004, 02:29 AM
Right now there's no possibility to access the frame buffer. If you use multipass techniques you have to use textures right now.

04-29-2005, 05:48 AM
Long time your posts are ago. So, is there now a possibility to access the framebuffer like you said in the topic??


04-29-2005, 05:59 AM
I believe this issue was considered a long time ago when they were designing GLSL. They talked about having built-in variables gl_FBColor, gl_FBDepth, and gl_FBStencil. From what I've read, they decided against these variables because they would be impractical to implement and have poor performance.

Have a look at issues 7 and 23 at the bottom of the GLSL spec. http://oss.sgi.com/projects/ogl-sample/registry/ARB/GLSLangSpec.Full.1.10.59.pdf

05-05-2005, 03:22 AM
Alright, then I have to find a different solution.

Thanx anyway