maximizing frame rates in X-Plane

[Keith Smith]

I recently built a new system and was briefly dismayed at the lack of performance in the recent XP9 beta release. To make a long story considerably shorter, here's what I learned (at least for NVidia cards, specifically the 8800 series)

 

- disable VSYNC on your video card (UPDATE: Or, leave VSYNC on but ENABLE 'triple buffering')

- reduce anti aliasing to 2x or 4x, rather than 16x

- reduce to single screen acceleration (if you have a multi screen setup). Note: this was highly relevant for me when running a GeForce 6800 GT, but doesn't appear to matter with the new 8800 GT. (EDIT: Perhaps the settings didn't take before. Single screen _IS_ faster on the 8800GT)

- feel free to enable pixel shaders and default reflective water

- avoid volumetric fog for now (reduces performance by about 50%)

 

Those first two items saw my frames go from a max of 60 to about 120fps. The combination of vsync being on, anti alias 16x and volumetric fog brought the system to its knees.

 

I'm now able to fly with:

- 'filled in' trees

- default object visibility

- 'tons' of objects

- 'insane' roads

- extreme texture res

 

at 50-100fps depending on where I am, with visuals like these...

 

http://www.tristesse.com/~keith/jpg/xplane/xp9/screenshot_20.png 1.7MB

 

http://www.tristesse.com/~keith/jpg/xplane/xp9/screenshot_24.png 1.7MB

 

http://www.tristesse.com/~keith/jpg/xplane/xp9/screenshot_26.png 1.9MB

 

http://www.tristesse.com/~keith/jpg/xplane/xp9/screenshot_27.png 1.7MB

 

http://www.tristesse.com/~keith/jpg/xplane/xp9/screenshot_28.png 1.6MB

 

Prior to making those changes, I was at the 19fps minimum, with fog.

 

I'm running different configurations to see which settings give the best bang for the buck, and a low anti aliasing setting seems to be the best compromise between jaggies and frames. To be clear, AA by itself doesn't kill your frames, but if you utilizie pixel shaders, v-sync, and heavy AA, the combination has a sinister effect on frame rates, at least on my rig (core duo 3.2GHz, 8800 GT 512MB)

Edited December 13, 2007 at 06:29 PM by Guest

[Keith Smith]

By the way, if you're an NVidia user, BEWARE of the NVidia Control Panel. After you change a setting, it appears as though you need to REBOOT, or at least log out and back in for it to take effect (that is definitely true for multi screen acceleration changes, at the very least).

[Tom Solon]

Look at that H20... amazing. Can't wait until my case and new OS arrives... I think Mrs. Claus is getting me XP 8.64 for Christmas. Hooray.

 

Amazing shots, and great tips.

[Brian Ratledge 962606]

Fantastic photos. Are they from Yosemite? Maybe i can get some pics from the same location in 8.64 for comparison.

[Keith Smith]

First one is LOWI (the new startup airport in xp9), the rest are in the Hetch Hetchy Reservoir in Yosemite, east southeast of Pine Mountain Lake airport.

[Jefferson Leeper 1038620]

Keith,

Thanks for the great post. I was just looking for this guidance! I have 4 quadcore, 4gb mem, vista home (?), Nvidia 8800GTX machines running 8.64 (9.0 ordered to install in a separate directory)

 

I experienced a huge increase in fps with vsync turned off. I'll add your other suggestions and advise.

Oddly, one machine sometimes seems to run faster than the next. Probably due to the difference in what it is trying to display ie left view vs right etc.

[Keith Smith]

Jefferson, good deal. When discussing frame rates, it's only worth doing apples to apples comparisons when tinkering with the settings. A few out the left window at a given point may give a m[Mod - Happy Thoughts]ively different frame rate than straight ahead, or the right window, based on what's being rendered. So, don't let that bug ya

 

Keith

[Jefferson Leeper 1038620]

Thanks Keith. I'll do an apples to apples comparison ie all with the same offset, and see. There certainly must be some benchmark software I could run on each and see if there may be a heat issue, a bad card etc. All three PCs are exactly the same, so they should perform very close.

Question: I see in the NVIDIA Advanced control panel the ability to change antilaising from 16x, 8x, 4x, 2x. I believe the default is "application controlled".

Did you mean change in X-Plane, or change it in the NVIDIA control panel?

[Keith Smith]

I leave it as app controlled in the panel and then make the change within X-Plane. I haven't tried setting it to none in xplane and then setting it on the card. When Xplane started supporting AA, I recall reading a release note saying you should set it within Xplane, but I could be wrong.

 

Heat shouldn't be slowing your system down...it would just crash it. Try setting the left and right screens to have exactly the same viewpoint as the master. I'm not sure if the flight model runs on those slave boxes...you'd think they'd actually run a little faster without having to run the model and only do visuals.

[Jefferson Leeper 1038620]

Thanks Keith. I'll make the settings in X-plane.

 

I'll try the same viewpoints and advise. I agree, the master machine should be a bit slower one would think!

[Wade Williams 877539]

Vsync and FSAA are two of the most detrimental effects to frame rate regardless of sim or game.

[Keith Smith]

Some pics on the new 1920x1080 rig here:

http://www.tristesse.com/~keith/jpg/xplane/xp9/canyon_run/

 

Shot #36 shows 35fps. I now get approx 60fps in that same area with single screen acceleration.

 

A replay of the flight is available as a situation movie in that directory (the 34MB smo file). Save it to xplane-root/Output/movies and load it up in xplane for a fun flight through the Grand Canyon.

[Jefferson Leeper 1038620]

Nice Pics! I'm running the dell 3007, so I have to push 2600x1600. FPS for me varies greatly, depending on where i am, but averages around 60.

If you pick a resolution in X-Plane that is one pixel larger than the card does, it doesnt like it (lesson learned)

[Keith Smith]

Jefferson, I tried 2048x1024 while using 2 x 17" screens (1280x1024) each and had a pretty big frame rate drop. At 1920x1080, the frames are pretty much identical to the 1280x1024 state. I'm guessing beyond the 1920, the vid card becomes a limiting factor, and an SLI setup may be in order.

[Jefferson Leeper 1038620]

Remember, mine are separate PCs networked, so no framerate drop by adding extra views. with the quadcore PCs, framerates are good at the 4x level with vsync off. I did start to get runtime errors. It could be HEAT related, or one of the settings I changed. For grins, I'll backtrack, and put the cards back to multi performance, and vsync on, and see if the runtime goes away....

[Keith Smith]

Unhappy with some of the tearing issues [Mod - Happy Thoughts]ociated with having vsync off, and also because a good friend was unable to find the setting to turn off VSYNC on his ATI card, I did more reading about how VSYNC as it relates to high performance gaming. The result seemed to be that with Open GL (which XPlane uses), if VSYNC is used, triple buffering should also be enabled.

 

I haven't done the reading to see what triple buffering is yet, but I'm guessing it decouples the generation of the frames with the small delay [Mod - Happy Thoughts]ociated with waiting for the monitor to refresh (at 60Hz), or something along those lines.

 

I was able to enable VSYNC, triple buffering, anti aliasing (8x), and pixel shaders. In areas where I would normally get 40fps, I STILL GOT 40fps. With shaders, anti-aliasing, vsync but NO triple buffering, I was in a world of hurt at 19fps.

 

However, with VSYNC, it's not possible to get more than 60fps (the refresh rate of my screen), but that is ABSOLUTELY FINE, it was never my goal to have absurdly high FPS...it was to get the most bang for the buck. A non-tearing 40fps display is outstanding.

 

So, moral of the story? If you want to use VSYNC with Open GL, also use triple buffering.

[Jefferson Leeper 1038620]

Thanks Keith. I'll try the triple buffering/vsync on option and advise. What does "tearing" look like?

 

I at times am moving along at high fps, then I'll sink to 19fps on the center machine (master) and have very jagged movement, and get the "too many rendering options" message. Other times it is well above at 60-80. I did add several custom scenery pacs in order to get the taxiway/runway signs at DIA etc. I'm not sure if that is contributing to a FPS issue.

[Reece Hunter]

Thanks for the tips KS.

 

My three-year-old PC, which ran 8.XX very nicely is on its last legs. My personal CFO (aka wife, honey, babe and other terms of endearment) signed off on a new rig complete with whatever video card, sound card, accessories I *need* to keep doing whatever it is I do with it (paraphrasing). Bottom line is can hardly wait to try them on X9.