[BUG] FS2020 CAS Shader implementation might have a bug

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TL;DR: FS2020 is supposed to be implementing the AMD FidelityFX CAS Shader already, but it seems there is a bug which is preventing the use of its superior “sharpening” properties in some cases.

NB: AMD CAS Shader is one component which is also used with AMD FSR Shader but it is not the same thing.


There are numerous reports of lower effective LOD ring distances. Besides the shorted distance beyond which objects are no longer drawing, ground textures are also very often cited as being directly affected by this and many a resorting to using Terrain LOD 200 at least to restore some of the texture sharpness in the distance, and some others are even manually changing the TLOD value in the UserOpt.cfg file to unprecedented values. I’ve seen 600% and more already since 1.18.13

In short, the game maybe shortening the LOD ring distances and therefore is displaying a lower res ground texture, which inherently shows as a more blurry ground texture and not too far from the aircraft, but it also shows right beneath the aircraft once above 20,000ft.


The main problem here to me is two fold:

  • There might be a real reduction of LOD ring distance causing this, but…
  • FS2020 is not fully using the CAS Shader either.

In effect, FS2020 is now using the AMD FidelityFX CAS Shader since a few versions ago. “CAS” means “Contrast Adaptive Sharpening” and it is a new technique used to enlarging lower res renderings into higher res displays, but unlike a simple bilinear filtering it also embeds an innovative CAS technique to restore crispness in the process.

Although there is a Sharpen setting in the UserCfg.opt file, I’m not certain it is either working, or if it is strong enough, in both these cases:

  • render and display at native resolution
  • render at a lower res (Render Resolution FS2020 setting) then display at native resolution.


To illustrate this, I’ve picked up a screenshot which was recently posted and I’ve used the FidelityFX-CLI app

NB: this screenshot is not native size but was taken with render scaling 110%. I’m still trying to get a screenshot in VR showing how the fuzziness is even more disturbing than 2D, nevertheless, this topic is also about offering the means for the end user to adjusting the CAS Shader sharpening strength, and to show give an example of how it could look like.

PS: I’d suggest you view these images in full res for better results


CAS 0.5 (no resize)

CAS 1.0 (no resize)

It is clear to me just applying 0.5 CAS sharpening makes the visual much more appealing even with the loss of LOD distance ring. However at 1.0 this might be creating too much noise artifact (I’ve seen some when testing with other screenshots).


The FS2020 CAS Shader is only used when Render Res. is lower than Display Res. (i.e. render resolution < 100%). Otherwise when rendering and display res. are the same, it seems the Sharpening mode of the CAS Shader is not used.


To wrap up, I’d like to suggest the following:

  • I’d suggest FS2020 uses the CAS Shader for its SHARPEN filter, even if render res. and display res. are the same
    <= 100% instead of just < 100%

  • I’d also suggest FS2020 is letting the user adjusting the CAS Shader SHARPEN strength
    → there is 1 shader parameter value meant just for this in the AMD CAS Shader code.

  • I’d also suggest to repurpose the UserCfg.opt Sharpening setting from integer (0 or 1) to float ( [0…1] ).

  • I’d also recommend the default CAS Sharpening strength be 0.5 by default
    → edit: 0.5 by default when rendering at or above display res - i.e. same res. or downscaling
    → edit: otherwise AMD recommended sharpen strength by default for the upscaling cases.

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As discussed in the other thread I have a feeling that the sharpen filter is stuck to the on position in VR regardless of the UserCfg setting, producing shimmering even at native resolution. Would be great to have more control over this.

the sim is doing so much sharpening atm it’s very noisy, especially when looking at vegetation, trees etc

The sim has AMD FSR built in the engine now.

But the over-sharpen is honestly evident, I agree with that. Also I am not sure what is exactly going on with the postfx in 1.19.9. It should be better, the AA is a bit better.
However it took me a day or two to notice the particular issue lots of users are reporting - that’s the increased amount of shimmering…textures ?
I don’t know where did that come from, it applies only to the stuff in the active part of the visible frustum, so it might not be the filtering issue.

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msg 428604/5

This is not public knowledge though. Instead they advertised they’ll implement the CAS Shader (which is one half of the FSR Shader) back in Nov/Dec 2020 and which they did implement (so it seems), but they didn’t provide user control on the CAS Shader “Sharpening” uniform which is what this topic is asking for too.


I’d love to get a sharpening slider, i made a wishlist topic for it some time back.
I thought the sharpening would be honestly unnoticeable with a high res display, but it’s still a mess.
I have disabled sharpening in the cfg and added a little bit of smart sharpening filters with reshade instead based on depth map.
It’s my temporary solution at this moment.
Would love to get proper sharpening back tho, the leather in the cockpit etc all looks greater with native sharpening

So, could any of the things I mentioned and especially that increased occurrence of shimmering have anything to do with possible changes/tweaks to the sharpening code or the AA they attempted post SU5 and in the latest 1.19.9 ?
I mean, it kinda bothers me visually oftentimes than not.

And you can’t use post-process sharpen in VR anyway…

I’ve done enough on my free time despite the love MSFT sends me back.

Better ask them than me :thinking:


Yeah, but they don’t wanna tell me :no_mouth: