Can someone please explain downsampling/ Nvidia DSR?

[MxGaza33]

After complementing the new Dynamic Super Resolution feature to a work colleague today after getting my new 970 it got me thinking on how downsampling actually works and improves the image. My understanding of downsampling is that the image is rendered at a higher resolution than your monitor is capable of, then scales it down to your monitors resolution which in my case is 2560 x 1440. In the case of Nvidias DSR a small amount blur is added to the image before it is scaled down.

 

The part I'm struggling to get my head around is what actually happens to the image when it is scaled down that improves it?

 

I'm familiar with the basics of how anti-aliasing works by blending pixels to make edges appear smoother, but how does downsampling achieve this same effect? You've still got the same same amount of pixels you started with, so without this 'blending' that anti-aliasing uses how can edges appear smoother?

 

Any help would be appreciated as I've been searching google but I can't find an answer and I can't stand not knowing! Haha.

[terrytek]

The pixels just get squeezed more compactly to allow for more pixels. Trust me, I'm using it, even though i have a bit higher of a load on my GPU now.

[MxGaza33]

The pixels just get squeezed more compactly to allow for more pixels. Trust me, I'm using it, even though i have a bit higher of a load on my GPU now.

 

I'm not doubting it works, I'm questioning how exactly it improves the image. If you have a square made of 4 pixels and you 'downsample' it to a single pixel, there is no way to show the 4 separate pixels anymore and only 1 is shown. Which would look exactly the same as rendering one in the first place. So your theory doesn't really make any sense, you can't "make room for more pixels" when the resolution of your monitor doesn't change.

[ZetZet]

I'm not doubting it works, I'm questioning how exactly it improves the image. If you have a square made of 4 pixels and you 'downsample' it to a single pixel, there is no way to show the 4 separate pixels anymore and only 1 is shown. Which would look exactly the same as rendering one in the first place. So your theory doesn't really make any sense, you can't "make room for more pixels" when the resolution of  your monitor doesn't change.

[terrytek]

I'm not doubting it works, I'm questioning how exactly it improves the image. If you have a square made of 4 pixels and you 'downsample' it to a single pixel, there is no way to show the 4 separate pixels anymore and only 1 is shown. Which would look exactly the same as rendering one in the first place. So your theory doesn't really make any sense, you can't "make room for more pixels" when the resolution of  your monitor doesn't change.

It's kinda the same principle as 4K. 4 super dense pixels the size of 1 normal pixel. And with 4K, you really can't see those pixels either.

[Glenwing]

It's super-sampling AA, except can be used in any game. Just look up how SSAA works.

[Laputacake]

I'm not doubting it works, I'm questioning how exactly it improves the image. If you have a square made of 4 pixels and you 'downsample' it to a single pixel, there is no way to show the 4 separate pixels anymore and only 1 is shown. Which would look exactly the same as rendering one in the first place. So your theory doesn't really make any sense, you can't "make room for more pixels" when the resolution of your monitor doesn't change.

Its like when you resize an image and make it smaller it looks better but just on games.

[DEDRICK]

It's the same as Upscaling(Scaling Filters).  Upscaling a 720p image into a 1080p requires an estimation to be made of what the nearest new pixels should look like, often it isn't the best.

 

Downscaling provides more data for the estimations (4x in the case of 4k to 1080p) thus providing more accurate and sharp images.

 

Scaling on the other hand should be obvious.  Watching a 720p video on a 1440p monitor, 1 720p pixel is scaled to take up 4 1440p pixels

 

Downscaling 4k to 1440p look like garbage because it isn't divisible evenly(AMD disabled the option to do it)

[MxGaza33]

It's super-sampling AA, except can be used in any game. Just look up how SSAA works.

 

It's is the opposite of Upscaling.  Upscaling a 720p image into a 1080p requires an estimation to be made of what the nearest new pixels should look like, often it isn't the best.

 

Downscaling provides more data for the estimations (4x in the case of 4k to 1080p) thus providing more accurate and sharp images.

 

Scaling on the other hand should be obvious.  Watching a 720p video on a 1440p monitor, 1 720p pixel is scaled to take up 4 1440p pixels

 

If this is the case then when the image is down scaled then it must be blending pixels, which ties in with it being Super-Sampling AA. Is this done by the Nvidia driver? (or other software if just downsampling)

 

What makes downsampling different from AA then such as MSAA?

[Glenwing]

If this is the case then when the image is down scaled then it must be blending pixels, which ties in with it being Super-Sampling AA. Is this done by the Nvidia driver? (or other software if just downsampling)

 

What makes downsampling different from AA then such as MSAA?

It's done by the NVIDIA driver I assume. And it really isn't any different, it's just SSAA. That's why DSR is so taxing. Just as taxing as SSAA in fact

[DEDRICK]

Super Sampling (also known as Down Sampling) Anti Aliasing is not always possible to inject into game engines.  DirectX 9 Deferred Renders for example can't do MSAA, only Post Processing AA's like FXAA or CMAA. Planetside 2 and WoW do not have MSAA or SSAA and it is not possible to inject them either.

 

DSR/VSR is happening outside of the engine.  It tricks the game into thinking your max display res is 4k, so the game renders at 4k and then your card downsamples the image to your Windows Desktop Resolution.

 

Shadows of Mordor this feature was built in(Planetside to can also do it if you edit the ini), I think Evolve has it as well.  It's the Render Quality setting in newer games, some games allow you to push it higher than 100%

[terrytek]

It's done by the NVIDIA driver I assume. And it really isn't any different, it's just SSAA. That's why DSR is so taxing. Just as taxing as SSAA in fact

It's so taxing, my GPU is idling at 60C. So watch your temps too if you just use DSR or SSAA.

[BurgerBum]

If this is the case then when the image is down scaled then it must be blending pixels, which ties in with it being Super-Sampling AA. Is this done by the Nvidia driver? (or other software if just downsampling)

 

What makes downsampling different from AA then such as MSAA?

i belive downsampling is the entire image, every pixel, while AA and MSAA are textures only?

dont qoute me on that though.

[BurgerBum]

It's so taxing, my GPU is idling at 60C. So watch your temps too if you just use DSR or SSAA.

^^^ this too, there is a drawback to it. ^^^

[MxGaza33]

Ahh it all makes sense now! I didn't realise downsampling was a form of AA, and that explains why it has such a big performance hit applying this to the entire image.

 

You learn something new every day, thanks!

[coen113]

I'm not doubting it works, I'm questioning how exactly it improves the image. If you have a square made of 4 pixels and you 'downsample' it to a single pixel, there is no way to show the 4 separate pixels anymore and only 1 is shown. Which would look exactly the same as rendering one in the first place. So your theory doesn't really make any sense, you can't "make room for more pixels" when the resolution of your monitor doesn't change.

It basically takes those 4 pixels, and calculates the average, that makes it look sharper

[DEDRICK]

i belive downsampling is the entire image, every pixel, while AA and MSAA are textures only?

dont qoute me on that though.

 

Pretty much.  SSAA the entire frame is rendered at a higher resolution then scaled down, MSAA the model edges are rendered higher then scaled down

[BurgerBum]

It basically takes those 4 pixels, and calculates the average, that makes it look sharper

in a sense playing 4k downsampled to 1080 is half as pretty as 4k and just a tiny bit more taxing than 3/5ths of 4k.

right?

 

kinda?

[DEDRICK]

in a sense playing 4k downsampled to 1080 is half as pretty as 4k and just a tiny bit more taxing than 3/5ths of 4k.

right?

 

kinda?

 

 

it is as taxing as playing 4k but not nearly the same quality because your monitor is only displaying averaged version, but it still looks better than 1080p would.

 

The game thinks you have a 4k monitor, so does your card in a sense.  With DSR/VSR enabled you can even change your Windows resolution to 4k

[BurgerBum]

it is as taxing as playing 4k but not nearly the same quality because your monitor is only displaying averaged version, but it still looks better than 1080p would.

 

The game thinks you have a 4k monitor, so does your card in a sense.  With DSR/VSR enabled you can even change your Windows resolution to 4k

okay,

teensey bit more demanding than actual 4k because it needs to average the 4 pixels, right?

[MxGaza33]

it is as taxing as playing 4k but not nearly the same quality because your monitor is only displaying averaged version, but it still looks better than 1080p would.

 

The game thinks you have a 4k monitor, so does your card in a sense.  With DSR/VSR enabled you can even change your Windows resolution to 4k

 

That's cool, just went into the Windows resolution and sure enough 3620 x 2036 is there. Didn't realise you could apply DSR to the Global settings aswell. Looks rubbish though, haha.