FXAA + Triple Buffering acts like regular VSync

Graphics / Linux Linux
1

Found a strange interaction effect between FXAA and Triple Buffered vsync.

If FXAA + Triple buffering is enabled then performance is low often dropping to a locked 30fps.

If FXAA is enabled with no VSync at all then performance is high i.e 50+ fps.

If FXAA is disabled but VSync with triple buffering is enabled then performance is high i.e 50+ fps

FXAA disabled + VSync with triple buffering disabled results in the same performance as FXAA + triple buffering.

This suggests that FXAA itself is not causing the issue, but rather FXAA and triple buffering don’t appear to work together.

MSAA + VSync with triple buffering = 50+ fps, so it’s FXAA specific.

Perhaps it’s by design, though, perhaps FXAA itself can’t work with triple buffering.

GPU: GTX 275
Driver: 310.14 (tried various 304 drivers as well, same issue)

2

What application?

3

The Witcher and Skyrim run under wine, but also the Unigine Heaven benchmark.

I’ve not tested to see if ingame FXAA (rather than forced with nvidia-settings) has the same issue.

4

I’m trying to attach nvidia-bug-report.gz files but it won’t let me as it seems to only accept image formats as attachments.

5

rename it as JPG ;)

6

FXAA and Triple Buffering are mutually exclusive in the driver, and I believe FXAA takes precedence if both are enabled, so yes your deduction is correct. This is working as intended.

7

Then maybe it’s time to update the tooltip? External Media

8

Agreed, although there doesn’t appear to be any mention of FXAA in the documentation either (README.BZ2 on my system), so perhaps those changes will both be coming in a future release.

9

Yes, that’s a good point. I’ve filed internal bug 1172418 to track the tooltip update, and we’ll look into what kind of additional documentation is appropriate for FXAA.

10

Just thought I’d note that FXAA built into a game does not seem to be affected by this. E.g playing Skyrim or Dishonored under wine with built in FXAA doesn’t result in drops to locked 30 FPS. Same goes for the linux native version of Serious Sam 3. I’m guessing that the way the driver forced mode works won’t allow for this to be fixed, but it’s good that games that support FXAA themselves will work without out large performance losses that regular VSync entails.