P3D V4.2/3 & VR - Single-Pass Rendering

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AerialShorts
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Joined: 22 Aug 2016, 06:43

P3D V4.2/3 & VR - Single-Pass Rendering

Post by AerialShorts »

Hey guys, might be preaching to the choir but I recently stopped using FlyInside for VR in P3D and went native VR support. Worked pretty good but I was getting the tiny stutters as I turned my head. I wasn’t using single-pass rendering.

I turned that on and my frame times went from a hair over 11 ms (which put me in reprojection) down to 7 ms (smooth as a baby bottom). Of course I turned all sorts of graphics details up even more but that now has less effect on frame rates.

I didn’t know that single-pass wasn’t enabled by default, but it’s not. You have to turn it on. It also can only be done on 10 and 20 series cards.

For those who don’t know what it is, the most common way to render for VR is for the CPU and GPU to draw one eye's perspective and then the other. The CPU and GPU do double the work of drawing the scene once.

In single-pass rendering, the CPU and GPU draw a field of view big enough to encompass both eye's fields of view but the GPU renders from the two viewpoints. This cuts the load on the CPU almost in half and in CPU intensive applications like P3D that’s a big deal.

It’s apparently a little finicky especially if you have used FlyInside. I enabled single-pass rendering and on P3D restart got a message that my video driver crashed because my video card was removed. There was more involved in recovering to where I could run single-pass, but to get P3D running again in regular stereo mode, I just edited the VirtualReality.cfg and .xml files in the ProgramData/LockheedMartin/Prepar3dv4.3 directory (going by memory but that should be close) using notepad to change single-pass to stereo.

I had to do some sleuthing to get the video driver thing sorted but it was running the DeleteGeneratedFiles utility in the main P3D directory that fixed it. Then I had to a number of accessory and airplane reinstalls, setting my P3D configuration again, etc, to get everything back as it was before. Not terribly painful but I only had to do that because I deleted all configurations by using that utility. I don’t know that it was having run FlyInside that caused the DXGI message but suspect it was. And as long as you are running FlyInside, I believe that blanks the P3D Virtual Reality menu. You have to uninstall FlyInside first. Also, if you are running FlyInside now, you’ll lose a number of handy features in FlyInside. The VR interface in P3D is pretty basic. Hopefully that gets fixed up a bit soon.

The option is in the P3D Virtual Reality menu under Settings. Highly recommended and the bonus is that after you go single-pass, any changes to increase graphics settings have half the CPU impact on frames that they do in regular stereo mode because the CPU is only drawing (a slightly larger scene) once instead of twice.

It makes a big difference if you are flying in VR.

Enjoy!
VR Simming with HP G2 - And Loving It!

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