GL_BLEND and fp pbuffer SLOW !

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.

Try to use FP16 textures instead FP32 for blending operations.

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 ?


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.

Blending operations are not supported with floating point pixel formats. Certain blend operations only make sense with RGBA values clamped to [0,1].