WGL_ARB_render_texture slow with NVidia

[epajarre]

After some testing I am coming to the conclusion that generating a texture with pbuffers and WGL_ARB_render_texture is disapointingly slow on my GeForce FX 5900 (ultra) card.

My search on WWW (including this board) seems to confirm this, but I would still like to ask for a confirmation from somebody with real practical knowledge, is this really (still) true?

To add insult to the injury my notebook with its Mobility Radeon 9000 which is otherwise not a real speed star seems to work pretty well with GL_ARB_render_texture.

My current result is that with the FX5900 it is fastest to render the image to backbuffer and then copy(sub) it to the texture.

Are suggestions for improving from this?
I am currently limited to official driver versions, I might consider a very reliable beta version if needed...

[ZbuffeR]

Pbuffers should be faster (providing that the generated texture is reasonably large).

Sounds a bit like my (solved) nvidia-only
perf problems with pbuffers :
http://www.chez.com/dedebuffer/

[epajarre]

I tried your test programs on my system (P4@3GHz, GF5900U, 71.89 drivers), the results seem to confirm my point (pbuffers suck)!

RTT 43 FPS
pbuffer+copytexsub 57 FPS
pbuffer+copytexsub("buggy") 35 FPS
backbuffer+copytexsub 94 FPS!

So using render to texture is slower than using pbuffer+copytexsub, but using backbuffer and copytexsub is the fastest way by far!

On my mobility Radeon I get the following results
(in same order as above):
43
25
20
28-34 (funny slow fps fluctuations here)

I suspect that one reason for these reults
is the high fillrate of FX5900 (when compared to
the Mobility Radeon or to the GF3 you had
used for testing). The fill rate gives good results with the backbuffer copy. Also the FX5900 seems to have expensive context switch when compared to the radeon (or the Nvidia driver just sucks :( )

[Matt Zamborsky]

try the newest 76.50 drivers. I got absolute different results.

RTT 142
PBUFFER + COPYSUBIMAGE 108
BUGGY 75
BACKBUFFER 102

I have FX 5900 too. I got this when I run the demo and didnt resize window, only drag it to see FPS.

[epajarre]

I will have to consider those drivers, unfortunately I cannot really try beta drivers in the "production environment" at the moment.

Anyways, sounds really promising.