View Full Version : GL_BLEND and fp pbuffer SLOW !

08-11-2005, 03:32 PM
I don't know what goes wrong today...
I create a floating point texture pbuffer, render a quad in this pbuffer, then I bind the pbuffer as a texture and render some geometry using the texture.
Everything works really fine.
Then if I enable GL_BLEND before rendering in the pbuffer, it goes insanely slow.
So if someone has a cue about that it would be really great and helpful.

Nikolai Timofeev
08-11-2005, 08:10 PM
Try to use FP16 textures instead FP32 for blending operations.

08-12-2005, 02:08 AM
What video card do you have ? Blending on floating point buffers is not supported in hardware on any ATI as far as i know, and only by the 6800 family for NVidia. Maybe you're falling back to software emulation ?


08-12-2005, 08:58 AM
the graphic card I use is a Quadro FX 4400 with the driver 77.18.
Actually it seems that the blending is not supported for 128 bit texture blending.
I tried to set it to 64 bits it seems to work.
Thanks for your replies.

08-24-2005, 11:28 AM
Blending operations are not supported with floating point pixel formats. Certain blend operations only make sense with RGBA values clamped to [0,1].