In this test case, I'm seeing a 5950 Ultra and even a 5900 XT smoke a 6800 Ultra. so I'd sure appreciate some insight as to what I'm doing wrong.
The usage scenario is volume particle lighting, ala Harris . For example:
<font size="2" face="Verdana, Arial">Now I haven't even tried any optimization yet because I'm completely baffled by the stats I'm getting. Here they are:
- Set up a 32x32 color-only FBO
- For all 183188 particles
- <font size="2" face="Verdana, Arial">Read back a 1x1 to 8x8 pixel region centered on particle loc (glReadPixels)
- Render QUAD particle into buffer with alpha blend
- 12960 ms - 5950 Ultra (FBO)
- 23274 ms - 6800 Ultra (FBO)
- 5268 ms - 5950 Ultra (system frame buffer)
- 5547 ms - 6800 Ultra (system frame buffer)
The first two are rendered to a 32x32 color-only FBO. The latter two are rendered to the bottom-left 32x32 corner of the default frame buffer (MSAA disabled of course).
This immediately prompts two questions:
- Why is the older card faster in each technique
- Why is the system framebuffer path faster than FBOs?
This is all on the same system with the same app and same rendering path -- only the graphics card has been changed.
Anyone have an idea what's going on here? --Thanks!
NVidia Driver: 1.0-7667
NVidia Cfg: AGPGART, 8x, Fast Writes, SBA