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DCS PD is crushing on the CPU!


GhastlyTT
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From my findings experimenting with my Reverb today... Try dropping your PD and watch your game become smoother. If you can settle on a smaller than 1.0 PD, you'll have a smoother VR experience. Crank SteamVR SS up a bit to compensate.

 

In other titles when you increase pixel density you tax the GPU, not the CPU. The problem with increasing resolution is never how many frames can the CPU send to the GPU. It's can my GPU handle the increased pixel load? In DCS on OB, I can run max settings at .5 PD on my reverb pro... it's blocky and shimmery, even at 500% SS, but it's smooth. Every .1 towards 1.0 PD affects the CPU negatively until it becomes the bottleneck. Why is this happening? Draw demand isn't on the CPU and texture files aren't fluid in size. Strange.

 

Anyways. I settled on .8 PD and have a smooth experience at 300% steam SS with medium settings and 2x msaa.

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umm what are your PC Specs?? My PC would croak at that SS in SteamVR.. lol!! ;)

 

 

EDIT: This is wierd I tried your settings PD in game was .8 and 300% SS in SteamVR and it looked fantastic and ran pretty decent I was surprised.. I will keep experimenting with the SS to see where the best balance is.. thank you for this finding I would have never thought it possible..


Edited by The_Nephilim

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!!!This is a game changer!!!

Previously even with motionvector I had drops below 45fps, and while reaching 45fps (asw on) i was experiencing some kind of a micro-lags that were destroying the feeling of smoothness. Now its gone, immersion is incomparable.

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Glad my findings are helpful. It really doesn't make any sense. Maybe ED will investigate. It sucks losing a little crispness to the lower PD but if you're familiar with the cockpit beforehand even .7 is not so bad.

 

Of note, I'm on a Ryzen 2600 at 4ghz, a 2080Super, and 32GB of RAM at 2933mhz. Cheers.

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I just tested it at .8 PD and 300% SS in SteamVR and it works great. I tried the F-16 free flight over the Caucasus and intercepted the A-10s off to your starboard, which I've done in the past and had stuttering, and this time it was silky smooth.

 

I'll probably tweak it a bit more later, but I've been awake for almost 23 hours and just took my no-go pills.

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Ya same here OD+ is great again, matter of fact i can use the same graphic settings that i use with rift s with the OD+ now. Doesnt solve every fps issue but makes big improvement on my CPU frametimes and FPS all verified with fpsvr

Intel 8700k @5ghz, 32gb ram, 1080ti, Rift S

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SteamVR SS increased is linear, in-game DCS PD is exponential. 1.5 PD = 225% steam. 0.8 PD with 300% steam is the same as 192% steam or between 1.3 and 1.4 PD. 0.5 PD with 500% steam (which won't necessarily work since steam default caps render targets at 4096, which is below 500% on reverb) would be the same as 125% steam.

 

 

Nevertheless, it would hardly surprise me if the recent WMR changes to its dynamic render buffer handling and viewport downsizing caused some new bug with non steamvr induced render target increases.


Edited by Chamidorix
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SteamVR SS increased is linear, in-game DCS PD is exponential. 1.5 PD = 225% steam. 0.8 PD with 300% steam is the same as 192% steam or between 1.3 and 1.4 PD.

 

Nevertheless, it would hardly surprise me if the recent WMR changes to its render buffer handling caused some new bug with non steamvr induced render target increases.

 

Ya thats cool and all but not the point, the point is 1.0 pd in dcs causes cpu overhead thus leading to a huge decrease in fps and increase in cpu frametime. Where as at .8 pd its a big noticeable improvement on CPU frametimes. So the point is why is PD hurting the CPU in dcs so it may indicate an issue that needs fixing...

Intel 8700k @5ghz, 32gb ram, 1080ti, Rift S

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Pixel Density


Edited by coldViPer
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Ya thats cool and all but not the point, the point is 1.0 pd in dcs causes cpu overhead thus leading to a huge decrease in fps and increase in cpu frametime. Where as at .8 pd its a big noticeable improvement on CPU frametimes. So the point is why is PD hurting the CPU in dcs so it may indicate an issue that needs fixing...

 

Thank you. Yes. That was the point I was trying to make.

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I may be wrong about the whole PD/SS relation, but the way I understand it, it is to be expected.

 

PD controls the resolution at which the game renders the image. Steam then takes that image and resizes it according it to supersampling settings. Obviously, the process of paining the image is more resource intensive than just upscaling. You can offset the reduced size of the rendered image (lower PD) with higher upscaling (higher SS), but some quality will be lost in the process. SS won't bring the detail that is not there in the first place.

But it's hard to compare subtle image quality differences in VR headset, so despite this, the net result may be worth it.

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Ok, Let me break it down some more. Supersampling is irrelevant here.

 

Game (CPU) interprets your place in time and space. Then, based on your settings it inserts detail and objects. Once it does this, it hands the frame and textures off to the renderer (GPU). On a reverb pro screen, with Pixel Density set to 1.0, the renderer says, "how many pixels do I fill? 9 million? OMG" and goes to work. It's hard on the GPU.

 

The scene should not change based on resolution for the CPU. It's the same "picture" until it's handed off to the GPU for rendering. So why does a lower pixel density reduce workload on the CPU when it's the GPU that gets the relief?

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some1 is right, there is nothing magical happening here.

 

On a HP reverb the game renders 2160x2160 pixels per eye at PD 1.0. On a Valve Index the game renders 1440x1600 per eye at PD 1.0. All this is happening on the main thread on 1 core of the CPU. Reducing the load to 80% results in a performance increase, but costs image quality due to the lack of original pixels to fill. Steam VR supersampling is happening after all that, it takes the resolution coming from the game and multiplicates it. This task is completely up to the GPU (which has enough ressources because DCS is badly bound on the CPU).

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I think it kind of depends on you hardware specs... i tried this on my specs and settings, the only variation was to turn Steam SS up to 300% and pd down to 0.8 and yes it did place the load on my GPU... it made my frames worse , as the GPU was now running in the red rather than the yellow. Which was sort of what i expected.

SYSTEM SPECS: Hardware Intel Corei7-12700KF @ 5.1/5.3p & 3.8e GHz, 64Gb RAM, EVGA 3090 XC3, Dell S2716DG, Virpil T50CM3 Throttle, T-50CM2 Base & Constellation Alpha + MFG Crosswinds V2, HP Reverb G2
SOFTWARE: Microsoft Windows 11, VoiceAttack & VIACOM PRO

VR Stuff:   My Settings for 3090 and G2 , My Settings for 1080ti , Shaders MOD for VR , Patch Status

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This isn't an RTS. From a CPU standpoint, increasing resolution doesn't add detail, objects, extra things going on in the presented picture. Reducing resolution doesn't reduce detail, objects, or things on screen. Pixel Density is resolution. Supersampling isn't part of the discussion.

 

PD should not impact the CPU workload. Regardless of PD/resolution, CPU should send the same frame to the GPU for rendering. This is the case for every other title. Something is off.

 

Leave Steam Supersampling at native resolution. Reduce PD and you'll see the CPU present frames faster to the GPU. Do not confuse this with GPU frame rate. The point I'm trying to make visible here is that PD below 1.0 can remove a CPU bottleneck if you're willing to sacrifice the sharpness of your picture.


Edited by GhastlyTT
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so both CPU and GPU frame times are reduced, if reduce the PD and leave the SS alone... I'm not sure i understand the "revelation" here... do less work less work will be done ... i admit i was sort of surprised about how much less work was done, but thats a square function in process... so i really should not have been

SYSTEM SPECS: Hardware Intel Corei7-12700KF @ 5.1/5.3p & 3.8e GHz, 64Gb RAM, EVGA 3090 XC3, Dell S2716DG, Virpil T50CM3 Throttle, T-50CM2 Base & Constellation Alpha + MFG Crosswinds V2, HP Reverb G2
SOFTWARE: Microsoft Windows 11, VoiceAttack & VIACOM PRO

VR Stuff:   My Settings for 3090 and G2 , My Settings for 1080ti , Shaders MOD for VR , Patch Status

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An analogy:

1. Teacher (CPU) tells student (GPU) to write a 2 page paper

2. Teacher (CPU) tells student (GPU) to write a 9 page paper

 

In both instances, the teacher's workload is constant: tell student to write paper. Only the student has to do more work. Telling the student to write a smaller or bigger paper doesn't change the load on the teacher.

 

The CPU requests the GPU to draw a picture the same way regardless of resolution. PD should not affect CPU workload if the GPU is not bottlenecking the CPU. CPU should stay constant as the idea of the frame doesn't change, yet in DCS, this is happening. .5 or 1.0, the idea of the picture is the same. Yet, at .5, CPU generates that idea faster. It shouldn't. Something is off. Maybe ED will see this and understand.

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This isn't an RTS. From a CPU standpoint, increasing resolution doesn't add detail, objects, extra things going on in the presented picture. Reducing resolution doesn't reduce detail, objects, or things on screen. Pixel Density is resolution.

 

This isn't a 2D game, there is depth and distance. With higher resolution you see more objects in the distance because there are enough pixels to display them and cause draw calls.

i9 10920X @4.8GHz, X299X HEDT mainboard, RTX3090 OC, quad channel 64 GB RAM @3600, Pico 4, HOTAS & Rudder: all Virpil with Rhino FFB base made by VPforce, DCS: all modules

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Just because you can't see it at a reduced resolution doesn't mean it's not part of the task presented to the GPU. Text in the cockpit is a blurry mess at .5 PD but it's still the same texture file. DCS isn't unique.

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err you are assuming that there is no work for the CPU except to pass it to the GPU... thats not how either DirectX or this game works...

SYSTEM SPECS: Hardware Intel Corei7-12700KF @ 5.1/5.3p & 3.8e GHz, 64Gb RAM, EVGA 3090 XC3, Dell S2716DG, Virpil T50CM3 Throttle, T-50CM2 Base & Constellation Alpha + MFG Crosswinds V2, HP Reverb G2
SOFTWARE: Microsoft Windows 11, VoiceAttack & VIACOM PRO

VR Stuff:   My Settings for 3090 and G2 , My Settings for 1080ti , Shaders MOD for VR , Patch Status

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I'm not assuming that. I'm pointing out that the task performed by the CPU at .5 and at 1.0 pixel density (or even 1080p and 4k) is the same. The scene is decided and set. It doesn't decide how many pixels it's drawn across. That's the GPUs job.

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