Curious Blur in Some Games

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Iamtheguy
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Curious Blur in Some Games

Post by Iamtheguy » 21 Dec 2021, 10:48

It seems to me that games with mandatory TAA like BF2042 and Borderlands 3 appears blurry even when the camera is not moving. This can be fixed if I use higher than native resolution scaling. At 200% resolution scaling, the image quality is exceptional. I'm curious what is the cause of this blur and why it is fixed by rendering the game at a higher resolution and then downsampling. Is it because that higher resolution gives TAA more information to work with? If so, then why does the game appear blurry without camera movement?

It is also possible to enable DLSS with 200% render resolution on BF2042. I do not perceive any visual difference from DLSS off, but it slightly increases my framerate in a CPU bound scenario while also reduces my GPU usage by 20%. What is DLSS doing when the render scale is set to above native?

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Chief Blur Buster
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Re: Curious Blur in Some Games

Post by Chief Blur Buster » 24 Dec 2021, 17:48

Iamtheguy wrote:
21 Dec 2021, 10:48
It seems to me that games with mandatory TAA like BF2042 and Borderlands 3 appears blurry even when the camera is not moving. This can be fixed if I use higher than native resolution scaling. At 200% resolution scaling, the image quality is exceptional. I'm curious what is the cause of this blur and why it is fixed by rendering the game at a higher resolution and then downsampling. Is it because that higher resolution gives TAA more information to work with? If so, then why does the game appear blurry without camera movement?
It's probably because TAA is metaphorically sort of like 2-dimensional interlacing (temporally shifting lower resolution screen elements, in both the vertical and horizontal axises). You've got lower resolution transparencies (e.g. rendered at half resolution) but shifted a partial amount of a large pixel the next frame, and so on.

If you have motion that follows the pixel-shifting behaviors of TEMPORAL Antialasing, then you see a resolution-reducing behavior.

An example is TestUFO Interlace, Vertical Motion, 1 UFO. Try different motionspeeds and vertical resolution will halve during interlaced video.
Iamtheguy wrote:
21 Dec 2021, 10:48
It is also possible to enable DLSS with 200% render resolution on BF2042. I do not perceive any visual difference from DLSS off, but it slightly increases my framerate in a CPU bound scenario while also reduces my GPU usage by 20%. What is DLSS doing when the render scale is set to above native?
Effectively, it's a workflow of upscaling an image using DLSS, then re-downscaling the image again to native resolution. So you've got two scaling steps occuring. If you are dealing with resolutions above native, then the scaling is repeatedly smoothing out the jaggie imperfections on the image, much like a super-sampled anti aliasing pass done two times (one by upconverting by DLSS, and again via downconverting back to native resolution).

At least that is what I think is going on. DLSS works on a lower-resolution image to create an improved higher resolution image, without needing to render at higher resolution. This is done in an offscreen frame buffer. Then that offscreen frame buffer is displayed (scaled again) back to the native resolution you're displaying at.

DLSS has enough performance headroom that this is an okay route of reducing DLSS artifacts while gaining some AA benefits -- you're just doing a hybrid compromise of super sampled AA via a faster-performance path (DLSS 2.0).

This is because doing higher resolutions via DLSS is faster than rendering at a native supersampled resolution. So you're effectively using DLSS to create the supersampled images, rather than natively rendering the image. And downscaling back to native resolution, which can hide a lot of DLSS artifacts while still having higher frame rates than supersampling (e.g. Rendering at 4K for a 1080p display).

So you can get a lot of supersampled AA benefits, yet having a slightly higher frame rate than a native-rendered non-AA image.

This "DLSS AA" trick is a legitimate compromise for getting the nice supersampled look without the same performance penalty of supersampling by intentionally rendering above native resolution.

I'm curious though, what's your pre-DLSS native rendering resolution? Sometimes enabling DLSS automatically forces the engine to render at a lower resolution, so your original pre-DLSS resolution may be below native resolution, and the 200% setting just simply means the below-native resolution now becomes above-native-resolution. I am definitely curious about the BF2042 workflow...

Framerate can increases while gaining AA benefits if your pre-DLSS resolution is slightly lower than native resolution, then the final DLSS'd resolution is higher than native resolution, then you downscale (for the supersampled AA look) back to native.
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Discorz
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Re: Curious Blur in Some Games

Post by Discorz » 27 Dec 2021, 05:02

I think I've read somewhere Battlefield/Frostbite games use lower internal rendering resolution. Then it tries to upscale it to 'fake' native resolution. They started using this after BF4. That's one way to achieve higher frame rate. So when u apply any antialiasing or even manage to fully disable, it looks worse compared to real native image.
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