Hi everyone,
The catchline: You are potentially leaving visual quality on the bench for no performance gain! Check your GPU usage, if it's not close to 100% you can do better! There, now that you are hooked....
The Situation:
I made a discovery for myself tonight while trying to help out a buddy. This could help anyone using steam VR, and conceptually anyone else on any other system via use of windows task manager performance graphs instead of Steam VR.
My buddy is using the vive and just updated his PC's ram. While using task manager to look at the usage of his new ram under DCS, noticed his GPU was only working 60-70% and he asked me if I knew why. I fired up my DCS to see what mine showed (I am a previous rift and vive user, now running the index) and found the same thing. Then i dove into the performance graphs to figure out why.
Steam VR GPU Performance Graph
To enable steam VR performance graphs, flip the toggle labeled as such in steam VR developer settings (I am using Beta)
The middle horizontal line on the graph represents an 11.1ms frame timing (90fps). Anything below this line will result in smooth 90fps. As soon as it goes above, the fps instantly switches to 45.
The top of the graph represents 22.2ms frame timing (45fps). anything above the 11.1 and below 22.2ms will result in 45fps. Anything off the top results in less than 45.
Colour coding is green (<11.1), Yellow (>11.1, <22.2ish), and red (>22ish). Note the graph turns red before exceeding 22.2 while still maintaining 45fps. Also note if you have turned off frame smoothing, you will see orange instead of yellow.
The Test Specimen:
Kept myself honest by doing all testing paused at the start of the Hornet's fly now, free flight, Nevada instant action. I recommend to actually apply this, do so paused in an environment where you do most of your playing (ie low level with lots of ground units, mid to high level with lots of bandits etc) as i think as soon as you hit the action, the empty desert tuning will be no good for you.
How to use it:
The further below the 11.1 or 22.2 (if above 11.1) lines you are, the less the GPU usage will be. Mine as i had configured was only working at 67%. So you can turn on features, up super sampling (if doing via steam vr, you need to restart to see the effect), etc to get closer to one of those lines, and while doing so will see no fps loss (provided you don't cross the line), increasing visual quality, and increasing gpu usage.
The GPU will approach 100% usage as the graph approaches either the 11.1 or 22.2 line. Above 11.1 it will switch to 45fps, and the GPU usage will drop again sharply. Above 22.2, visual quality will continue to increase, GPU will be pegged at or around 100, and the fps will drop since the GPU can't give any more.
My results:
I am running the index, and a GTX 1080,
With textures hi, view dist medium, 1024 displays, and everything else off, at 80% super sampling via steam I can just barely maintain 90fps with nothing going on (ie the start of that instant action).
I hate the no shadow look so I usually play with shadows low, terrain shadows flat, Cockpit global illumination, at 100% steam SS, and get steady 45fps when not in a city/airport, with something like 15ms frame timing. This results in only 55-65 GPU usage for me.
Tuning via the graphs, in that fly now as detailed above I was able to up the visibility range to high, and the steam SS to 170%, and still maintain the same fps most of the time, but now in the 90% usage range. I tried changing other settings up and down one at a time, and you can see their relative impact on the graph, but none had as large an effect as the increased SS for quality to me. It seems (and makes sense) that as you increase the SS, the impact of the other settings also scales up accordingly. In any case, I was quite impressed that i can actually now read the MPCD!
You may prioritize different settings, the idea is the same... get close to the line, but don't cross it. I'll no doubt have to go back and reduce my settings somewhat for actual play.
The attached pictures were taken with my phone through the headset lenses where applicable.
