GLSL and frame buffer reads??

filiga · 08-11-04, 02:44 AM

Hello.

I did some GLSL programming, but quickly came up with a problem: Frame buffer reads do not seem to work at all. I'd like to do custom blending functions where one needs to have access framebuffer color and depth values (gl_FBColor and gl_FBDepth). Based on the GLSL spec I found frame buffer reads are in the experimental end of the GLSL feature set. Thus hardware and drivers may not support it at all.

Does anyone know if this is a HW issue, a driver issue or what?
Should I expect the situation to improve?

Here is an example of a compilation log I get:
(5) : error C1008: undefined variable "gl_FBColor"

And below is a sample fragment shader that would not compile:

void main (void)
{
gl_FragColor = gl_FBColor + vec4(0.2, 0.1, 0.1, 1.0);
}

I am using 61.06 drivers with an FX 5700 board.

filiga · 08-11-04, 03:43 AM

Mmmm...

Read the documentation more carefully, and it seems frame buffer reads are not really allowed in the current spec. Guess I'll have to use texture rendering and other tricks to do the work...

08-11-04, 02:44 AM	#1
filiga FX 5700 Join Date: May 2003 Posts: 8	GLSL and frame buffer reads?? Hello. I did some GLSL programming, but quickly came up with a problem: Frame buffer reads do not seem to work at all. I'd like to do custom blending functions where one needs to have access framebuffer color and depth values (gl_FBColor and gl_FBDepth). Based on the GLSL spec I found frame buffer reads are in the experimental end of the GLSL feature set. Thus hardware and drivers may not support it at all. Does anyone know if this is a HW issue, a driver issue or what? Should I expect the situation to improve? Here is an example of a compilation log I get: (5) : error C1008: undefined variable "gl_FBColor" And below is a sample fragment shader that would not compile: void main (void) { gl_FragColor = gl_FBColor + vec4(0.2, 0.1, 0.1, 1.0); } I am using 61.06 drivers with an FX 5700 board.

08-11-04, 03:43 AM	#2
filiga FX 5700 Join Date: May 2003 Posts: 8	Re: GLSL and frame buffer reads?? Mmmm... Read the documentation more carefully, and it seems frame buffer reads are not really allowed in the current spec. Guess I'll have to use texture rendering and other tricks to do the work...