float pbuffer rendering

Hi, does anybody encounter the same problem as mine? I am trying to render a float volume in a float pbuffer and I found the frequent CTT (glCopyTexSubImage) killed me, which will take near half a second every time creating a 512 size texture. My program is run on Geforce 5800 Ultra, driver version 43.45


If performance is important (or desirable), do not use CopyToTexture with floating-point textures/pbuffers. Use render-to-texture instead.

I see similarly poor performance on Linux (under the 43.49 drivers). Unfortunately, AFAIK I have no fall-back to render-to-texture (which is Windows only at the moment).