P3d v5 - multichannel vs singlechannel performance

Any issues, problems or troubleshooting topics related to the additional features present in the Prepar3D Professional Plus client application.
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P3d v5 - multichannel vs singlechannel performance

Postby sgst » Thu May 14, 2020 11:08 am

I have a p3d set up using multichannel and viewgroups. 1 host and 3 clients running visuals. All high end computers.

With P3D v5 I understand that performance is more GPU dependent and less CPU dependent compared with previous versions.

If I upgrade to v5, will it be possible for me to run just 1 high end CPU computer with 3 high end GPUs for visuals, and get the same or better performance than the multichannel set up? This would be a great advantage both from a cost perspective and a practical perspective.

I would be grateful if someone who has actual knowledge of this would respond, as it is quite an investment to make if I would make the transfer to V5 only to discover that I will still need multichannel, being really expensive.

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Re: P3d v5 - multichannel vs singlechannel performance

Postby Trifit65 » Sat May 30, 2020 4:28 pm

Thanks for your comment. As a user, I too noticed CPU bandwidth limitations whenever Multichannel is engaged (using Version 4) and would be really happy to learn that Version 5 is more GPU dependent.

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Re: P3d v5 - multichannel vs singlechannel performance

Postby whitav8 » Fri Jun 05, 2020 6:35 pm

Many training simulation developers are using three HD monitors driven by a SINGLE gpu card. Most Nvidia cards have three DP outputs and a fourth HDMI or some similar combination. There is no need or value in having three GPUs since the Windows 10 CPU and graphic system can only draw one screen at a time - assuming each screen is a separate view (NVSurround doesn't do that ). The real limiting factor is the computation of each of the views so that is why it is still important that the CPU be as fast as possible. I would recommend an Intel 9900K running at 5.2 Ghz (All cores) and a single Nvidia 2080Ti if you want to generate a large FOV (maybe 210 degrees) with three screens. If you tune it (minimal traffic, medium settings ), use high performance scenery (either medium complexity or that which has been tested and found to be high performance ), use a real cockpit or a virtual one that also has been tested for high performance (each developer is different ), you might get as much as 60FPS on each screen, but more likely 45 FPS. SLI won't help and the only reason for another GPU card is to drive some more 2D panels like an instructor station or possibly several small HD screens for the instrument panel on a simulated physical cockpit. Nvidia does provide a concept called single-pass for stereo VR, but I'm not sure if that can somehow be used for three separate view screens.
P3Dv5, P3Dv4.4 9700K@5Ghz, 32gbRam, RTX2070,HP Reverb HMD

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Re: P3d v5 - multichannel vs singlechannel performance

Postby NWittje » Wed Jun 10, 2020 8:53 am

@whitav8 : can you clarify/post some background reference for me regarding your statement about the Win 10 rendering system?
At one customer, I run a PC running P3d4.5 with a highend CPU and three GTX970, each connected to one projector, rendering via viewgroups with 3 images, and the customer claims much higher performance then single GPU setup (before). My assumption was that each card is able to only preload own textures etc for their FOV (GlobalTerrainView=True) into their memory.
@developers: Is there any more exact documentation what is loaded and rendered how and when?

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Re: P3d v5 - multichannel vs singlechannel performance

Postby neilhewitt » Sun Jun 14, 2020 5:02 pm

I have experience building both multi-channel (P3D Pro Plus / Wideview-based) and single-channel systems, and I believe the answer is (and always will be) 'maybe'.

Can you run 3 external views on a single machine and get decent performance? Yes, provided your machine is fast enough, but that has to be a qualified yes. CPU is always the deciding factor, unless your GPU is positively ancient or you insist on turning on every single graphical bell and whistle. Performance depends on what your setup is, what add-ons you are running, and where you are flying. It's all about the trade-offs you are willing to make.

As an example: My current setup is a dual-channel system using Wideview. The host PC runs all of my controllers and all of my instrument displays. The client PC generates a 180 degree outside view using two windows. In SW England with ORBX True Earth GB, a Carenado (ie non-study-level) aircraft, and scenery set to Dense with most other sliders right(-ish), I can get 45-60FPS across the two views. In central London, though, that drops to 18-25FPS. If I close one of the two views, that increases to 40-45FPS. My GPU (an RTX 2080 Super in that PC) is maxing out at about 30% usage, so it's the CPU that's the issue. There's been some FPS improvement in P3D v5 over P3D v4.5, but not a huge amount for me. Dropping the scenery complexity, as with 4.x, gets me more extra frames than any other setting change. I used to have to fly on Sparse in London to make it flyable, but with the better control response at lower frames in 5.x, I think I can push it to Normal with v5. But that's as high as I can go if I want to fly in London with complex add-on scenery and a demanding aircraft. And this machine is extremely high-spec. If I added a third view on this machine I would expect frames in the low to mid teens at EGLC. There are just hard limits in terms of what you can expect from a single PC.

I know I could get better performance in London using a three-channel setup with two image generator PCs, but then I would have to deal with the visual sync issues that come with Wideview, and as the dividing line between views is directly in the centre of the screen, those are all-too-noticeable. Nothing like having your runway tear in half on final. Or else it's P3D multi-channel and 15FPS half the time (because frame sync just doesn't work very well without hardware genlock) and even then the views will go out of sync from time to time. That's why I stick to a two-channel setup with one machine doing all the outside views. But as and when I move to a bigger sim with 3 projectors vs my current 2, I will no longer have that option.

There is no magical trick to get a massive FPS boost in multi-view setups. I've tried multi-GPU setups and they are no faster than single-GPU, multi-monitor setups for me - in fact, they were usually slower. And in P3D v5 right now, when I attempted to spread the rendering across two GPUs, all I got was either the dreaded DXGI error and one GPU failing, or an immediate crash and reset of the machine - not even a CTD or blue screen.

Which is a very long-winded way of saying: without trying it on your particular setup, there's no easy way to predict what the results will be.

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Re: P3d v5 - multichannel vs singlechannel performance

Postby KaseLite » Tue Aug 25, 2020 10:37 pm

I have been running 6 (5 with viewsgroups, 1 GPS) monitors on two RTX 2080ti with 1 CPU (i9-9900K) using V5 (and 4.5 before). No matter what i did i could not maintain a decent framerate, unless i dropped the sliders down. I eventually tracked it down the CPU load, ability to load content fast enough and render buildings... this intersection always produced the stutters. With reduced ORBX content and reduced building complexity i could maintain around 25FPS in VFR conditions until flying over places like Seattle or LA CBD where building complexity is high... then it would drip to 18/20 FPS.

So, i have switched to three-way multichannel using V5, WideView, WideTraffic and OPUS. Config is:

1 RTX 2080 TI & 9900K with 1x 3440x1440 & Realsimgear
1 RTX 2080 TI & 10700K with 2x 2560x1440
Then i span the screens with viewgroups (this gives 180 degrees) - i have found view groups still work the best vs. using what comes with WideView/OPUS for view management.

The performance of this setup is AMAZING for visual VFR flying. I can run each sim to the max both with ORBX, building, trees, tessellation, weather. Each group of monitors renders at 70+ FPS (but i limit it to 30 FPS). Finally i'm happy with performance and visual immersion...

Of course, this approach is not cost effective... a most cost effective approach is to stick to 3 monitors with 1 GPU/CPU, you can still get really good FPS (but not max in my experience) and its a whole lot easier to setup and maintain. But you cant get 180 degrees this way unless you use projectors and 180 degree screen (need lots of space :)).

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Re: P3d v5 - multichannel vs singlechannel performance

Postby wuhanboy » Sat Oct 31, 2020 2:07 pm

Dear sir,can you tell me how to config the multchannel and view group management? especially the gridsetup,left right bottom top and so on, I'm so hard and cannot to setup these? I have three Projectors.

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