Let's talk about Render Scaling - Why? Advantages? Disadvantages?

If the following statement is wrong, someone will correct me, I am sure, and I will edit accordingly so as not to add to the confusion.

Render Scaling allows the user to select either a higher or lower resolution to be rendered by the GPU than the display resolution. Ideally we want to have the display resolution set to the monitor’s native resolution for best results.

I understand why I would want to render at a lower resolution and then display the image at the native resolution. Doing this will reduce the GPU workload and so preserve usable performance with a marginal system.

What I do not understand is why I would want to render the image at a higher resolution than my monitor can display. I have a 2060 super connected to an HD 1920x1080 60hz monitor. At native resolution and render scaling at 100% I get locked 60fps performance with my GPU running at around 80-90% and CPU cruising at 60%. I have most graphics settings on Ultra and LOD at 100 for both terrain and object.

The only drawback I currently deal with is that displayed on a 32" monitor sitting about 36" in front of me, I need to zoom in to be able to read the smaller print on some of the instruments just because of screen resolution. Not a deal breaker. I have tried upping the render scale to try to improve the clarity in the cockpit, even though, to me, this seems completely useless. I do not see ANY difference between rendering at 4k and displaying at 2k. Don’t see how it could. My monitor is still only displaying 2.074 M pixels no matter what resolution the picture is rendered at.

There-in lies my title.

  • Why would I use a higher render res than my monitor can display?
  • Is there a significant advantage that I am missing?
  • Other that workload sent to the GPU, are there any significant disadvantages?

In short…

  • If you use render scaling other than 100%, why?

Please try to keep this purely educational and let’s try not to attack anyone’s opinion.
(Although, this really isn’t an opinion discussion. I would prefer facts and data to help me and others like me understand this.)

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Watching this with interest.

Jim-Sim

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Most people render it at a higher resolution so that the GPU renders a lot more detail within a given area. Then an interpolation algorithm will kick in to combine the pixels together into a single pixel to be displayed to your monitor.

Depending on the algorithm used, it would give you more detailed and accurate colours than you would in a native rendering scaling.

For example, on 100 scaling. The GPU renders one point as a single pixel. Let’s say a white colour. But on 200 percent scaling, the GPU renders the same spot as 4 pixels. And each of these pixels can be different colours due to the extra detail that it’s rendering. Let’s say we have 2 whites and 2 blacks. With the interpolation algorithm used when it’s pushing all 4 pixels to the display, now it’s taking the 2 whites and 2 blacks together do some calculations and displays it as grey.

So when you compare the two, the 100 percent only displays a single white pixel. While the 200 percent displays a grey pixel in the same spot simply because it renders a little bit more detail with the black pixels together.

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There was a big blowout around this in one of the threads just a few days ago, searching for “super sampling” or “SSAA” should find it… It was pretty funny.

Edited to add one of many useful posts from that thread:

In short, render scaling higher than 100% is a way of making the sim use a form of SSAA, or super sampling anti aliasing. I don’t use render scaling above 100% since I have a 4k monitor with only an RTX 2070 Super, but it seems some people with lower resolution monitors have great results with it. I use render scaling of 80 or 90% for performance.

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The facts for my situation are simple:

  1. I can’t give you technical info.
  2. lowering Render Scale results in a blocky mess without a whole lot of performance improvement. GPU yes but there were other issues where I was when I last tested.
  3. despite the fact that my monitor is 1080, raising Render Scaling makes things sharper and much more enjoyable. It can reduce many of the sims seemingly built in artifacts like those that occur in the clouds. it also taxes the GPU. I see it as little different than nVidias built in DSR.
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Read that thread. Thanks for linking it though because there is some good information.

Does not help me get my head around the perception of greater clarity. I may be totally obtuse but, my understanding of anti-aliasing is to give the perception of smooth lines when they are not either perfectly horizontal or vertical. For those of us that have messed with things like sprites back in the day, the ability to create a quality 3d object on a piece of graph paper 16 squares x 16 squares using no more than 256 colours, the importance of blending colours to curves to remove pixilation is old hat.

What still makes no sense is that to achieve that smoothness of curves we actually have to blur the image, not make it sharper. 4K or even 8K rendering will absolutely produce a nicer looking landscape when displayed at 2K but at the expense of fine details. The ONLY way I am aware of to get more detail is to increase the number of displayed pixels. Am I wrong?

I have read several threads recently about certain problems since WU6 came out, where the problem occurs only if you have Render Scaling set above 100%.

That by itself my be the ultimate reason to leave it at 100%.

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Yeah, agree. In this context the goal is to produce a visually pleasing image. There are two aspects to that:

  1. How many pixels do we have
  2. What value do we assign to each pixel

Render scaling has nothing at all to do with the first point, that is determined by the monitor resolution. Render scaling is all about the second point. It does not add detail, but it is able to assign pixel values in a way that gives a more pleasing image that subjectively looks sharper.

It is not a priori obvious to me that increasing render scaling automatically results in better pixel value allocation that results in a more visually pleasing image, although one could probably make good points around the Nyquist sampling theorem and around the amount of information available to the final rendering pass algorithm to make it plausible. I also think it is simplistic to consider only the “200% render scaling with 4 to 1 per pixel averaging down sampling” case since that is just one of infinitely many possible algorithms, it does not sound optimal to me, and it does not work at say 130% render scaling.

But it turns out empirically that when you try it, using the clever algorithms GPU vendors have implemented, it works. I am sure that there are scientific papers that can explain exactly how and using what optimum algorithms, but that is a level beyond my technical expertise in this area.

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In theory yes, however FS2020’s TAA is pretty lousy, or heavy handing in smoothing out the image. Which is needed because even if you use render scale 200 (2xSAA) and no further AA, the pixel crawl and shimmer with things in motion is unbearable.

Renderscale 200, no AA (thus 2xSAA) looks great on still images, but you need temporal AA to make it look good in motion.

Anyway FS2020 shows a big difference in detail between renderscale 100 and renderscale 200


Just look at the detail in the grass and the windows on the buildings.

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That is correct.

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Good examples. Interesting that although the building and window details are enhanced and grass has better shadows, I would (subjectively) submit that the more distant ground textures look more natural to me.

Still, very good representation.

Yes, this was an excellent example.
Thanx.

I expect you meant the, “thanks”, to go to @SvenZ ?

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I Also have a 2070s and usually run on 80% render scaling for better performance but due to the night time lighting bug from WU6 Ive had to increase RS to 100 and it actually runs very well with all settings turn up to high / ultra

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Basically every thing Neo said,

I am in 4k and typically do 100 render scale – however, at times, I’ve done 105 or 110… (a) to make the text more clear on the instrument panels (i.e. FBW A320) and other times because (b) I think it would make the sim look better (although this has no real impact I’ve come to realize)

I wish I have enough room in my measly RTX 2080 Ti to render 4K at over 100 scaling. Hahahah.

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More natural is subjective of course. Fun fact is that many people prefer mp3 versions of songs (chose as better quality in double blind tests) over their uncompressed natural sound, simply because they’re used to listening to those versions.

Another observation. I have been switching between FS2020 and Road 96 (actually have them running at the same time, alt-tab for in flight entertainment). Both render at 1080p, yet Road 96 (cell shaded with SMAA) looks a lot sharper than FS2020. Of course that game is mostly static scenes so doesn’t have to be as aggressive in fighting pixel crawl and shimmer.

It’s a tough balence. You still get odd moire patterns on AI generated buildings in FS2020, you can’t get rid of all rendering artifacts. Actually moire patterns happen irl as well. Pixel shimmer as well, except you wouldn’t call it pixel shimmer. But if you walk towards a chain link fence with another one behind it, odd visual effects happen.

Anyway, the main advantage from the higher render scale for me is instrument readability. It would be nice if they were left out of the TAA treatment and rendered with precision. Maybe it was like that before as I always had a sort of half line gap around the glass cockpit instruments, shimmering around the edges. (And glass cockpit rendering was a big resource hog) I find them harder to read since SU5. Renderscale 200 clears them up, yet halves my fps.

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my main problem is when i increase render scaling to 120 for example, it will increase the input lag, i don’t if someone have a solution to this issue ( i have an RTX 2070S and an i7-10875H)

hahaha - hey I used to have a 2080 Ti and it was and is an awesome powerful card… my 3080 isn’t that much better. Sure wish I had a 3080 Ti though, LOL

It seems right now, this topic can also reference the render scaling night lights bug. If you want night lights you must make sure the render scale is ONLY AT 100%. Thought this would be a hot fix by now. I use Reverb VR and lowering the rendering improves performance quite a bit for me.

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