View Full Version : Framebuffer blit on float targets

10-23-2008, 09:04 AM
I have a lot of problems with FBOs and multisample FBOs when using float as the internal format.

1 Draw scene to Float Multisampled FBO (called FBO_MS) (renderbuffers as storage)
2 Blit FBO_MS to FBO2 ( textures as storage)
3 draw textures from FBO2 to fullscreen quad in order to apply final tonemapping shader (etc)

A: texture target is NPOT GL_TEXTURE_2D (RECTS have been tested with the same problems)
B: all floats are GL_RGBA16F_ARB
C: all depth buffers and depth textures are GL_DEPTH_COMPONENT
(D: There are no problems rendering regular float textures)
(E: There are no problems if the internal format is of standard RGBA8 type for example)
(F: There are no problems to blit from MS float FBO to RGBA8 FBO)

I have severe problems with this on my Mac even though all extensions seem to be supported. Do other platforms have issues with this as well? (Right now I can't test my code on a Win or Linux PC)

It seems like the problem is located in glBlitFramebuffer.

The result is that the computer slows to a halt, gets garbled graphics and finally freezes completely. Feels like there is some random write to system memory or so :(

Keith Z. Leonard
10-23-2008, 09:13 AM
What hardware? I do exactly those operations with those formats in my engine and have not seen problems on PC.

10-23-2008, 09:15 AM
For what it's worth, I've no problems whatever with G80/Vistax86. I also use rgba16f and dc32, blits left and right, without and without stretching, with and without linear filtering, with and without MSAA resolve (no tex rect for me though).

10-24-2008, 04:08 AM
Alright. I'm back.
Mac OS X 10.5.5 and GF8800 (and GF 8600M)

I ported the code to windows today and it ran flawlessly. So Mac drivers are to blame. Thanks for your time anyway.