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TOPIC: Dithering and HDR

Dithering and HDR 1 month 3 weeks ago #1

  • moriz1
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not really a request: is the dither shader still useful in any way? its description makes it sound like it's only useful for people with really bad monitors that can't display a full range of colors.
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Dithering and HDR 1 month 3 weeks ago #2

  • crosire
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moriz1 wrote:
not really a request: is the dither shader still useful in any way? its description makes it sound like it's only useful for people with really bad monitors that can't display a full range of colors.
It's not about the monitor. You can have the most expensive setup, but it won't help you: Almost no game outputs in more than 8 bit per color channel (because of limitations of the Direct3D drivers, the maximum is 10 bit anyway). 8 bit are not nearly enough to have smooth color transitions. That's why you get banding artifacts. Dithering is one way to hide these artifacts by deceiving the human eye. However, it only works if you have HDR input (that is, more than 8 bit per color channel), so in case of SweetFX it could only be applied to the result of SweetFX effects (since the shaders itself run with 32 bit per channel), NOT the game output, and is thus only useful in very rare cases, for instance if you applied extreme contrast boosts.
Cheers, crosire =)
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Dithering and HDR 1 month 3 weeks ago #3

  • JBeckman
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There was another similar shader that greatly smoothed out banding as seen in several games with for example their skybox though.

Interesting to hear that about color bits and d3d, I assume DirectX 11+ has some improvements over earlier API versions then as for textures there's support for BCD or what they're called and "deep color" formats at I think it's 30 something instead of 24? I'm not that good at these things as is pretty evident though. :)
(Well there's different things for these I suppose, color "depth" and color "bits" or some such.)

That and we're now starting to see games pushing for HDR support and that at the minimum requires a monitor or TV with 10 or higher bit support for color, 12 I think was better but that's not too common so there's various levels of HDR support and specifications from what I've read. (Up to some pretty extreme brightness or luma values or what it was, far above what is common today at least even in high-end monitors outside of the usual consumer products and also newer TV's though it seems those support HDR better at the moment.)


I guess another important part is that even 10-bit monitors are often 8-bit with frc dithering far as I've read at least, similar to how there are 8-bit monitors that are 6-bit with frc.
(True 10-bit or above is likely more expensive I'd imagine then.)

EDIT: Going back to that shader effect though I remember there were some small blur as a result of using it and possibly also "noise" in the form of a light film-grain effect.
Last Edit: 1 month 3 weeks ago by JBeckman.
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Dithering and HDR 1 month 3 weeks ago #4

  • crosire
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HDR in games is a different topic. It means that the rendering pipeline is using a target with more storage space (usually 16 or 32 bit per channel). The final output still goes to 8 bit, games use tonemapping to bring the HDR range back into that small space (LDR). It's not because HDR is more expensive (it makes no difference), it just takes up more storage space. As to why 8 bit is still used in drivers, that has most likely historical reasons and because little hardware supports more.

I don't know of anyhing called "BCD". There are "BC" formats, which stands for "block compression" and simply means that textures are stored compressed. Nothing fancy there, Direct3D 9 has those too, just differently named. These are used for static game textures usually, to save GPU memory, but can't be used as render target and therefore don't have anything to do with HDR. When talking about 24bit vs 32bit formats, it usually means all color channels combined: RGB8 = 24 bit (3 * 8 bit), RGBA8 = 32 bit (4 * 8 bit). The former is not used anymore (hasn't been since D3D8) because it doesn't work well with modern hardware and alignments. But as you see "32 bit texture format" most of the time refers to the 8 bit per channel I mentioned, not 32 bit floating point per channel.
Cheers, crosire =)
Last Edit: 1 month 3 weeks ago by crosire.
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Dithering and HDR 1 month 3 weeks ago #5

  • JBeckman
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Ah I see, thanks for clarifying that, it's going to be useful to know. :)

And yeah it was indeed "BC" not "BCD" I mistakenly added "Data" as I thought it was Bitmap Compressed Data. :)
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Dithering and HDR 1 month 3 weeks ago #6

  • Martigen
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JBeckman wrote:
There was another similar shader that greatly smoothed out banding as seen in several games with for example their skybox though.
...
EDIT: Going back to that shader effect though I remember there were some small blur as a result of using it and possibly also "noise" in the form of a light film-grain effect.
That shader is Deband and it's already in Resahde 3.0.
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Dithering and HDR 1 month 3 weeks ago #7

  • Sunesha
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LOL, I had same question today. I tried out Deband as I was suggested. It has the same effect and in my 2 cases it worked out better I believe
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Dithering and HDR 1 month 2 weeks ago #8

  • Abby
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  • 1828=8+(2x10)+(8x100)+(1x1000)​=8+(2xm)+(8xn)+(1xw)
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And my HDR set can explain the beauty of this topic lol
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