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semler

3D PBR, Substance Painter and Tonemapping

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Hi,

I'm curious as to what others do wrt tonemapping when it comes to authoring materials for PBR in programs like SP. To my understanding the default tonemapping in SP is a simple sRGB, but it supports using a 3D LUT.

Many modern engines use a different tonemapping to get a more filmic(?) look, like the ACES in Unreal, so does your team use the default sRGB when authoring or does it use a custom LUT?

Henning

 

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21 minutes ago, semler said:

Many modern engines use a different tonemapping to get a more filmic(?) look, like the ACES in Unreal, so does your team use the default sRGB when authoring or does it use a custom LUT?

sRGB when it comes to Albedo.

It's like the 8bit normal map vs 32bit. Although 32 bit is much sharper and can store complex data it's almost never used. Because the deference between them isn't worth it.

Same with sRGB. Filmic options do give better range for lights to work in and with bloom and GI it does matter, just not by so much that people are willing to rebuild years worth of libraries for it.

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I can see now that my question could be misunderstood. Sorry for that :)

 

What I meant to write was: while creating the materials, the viewport in substance painter can show the final result (with IBL applied), either using sRGB as default or using a custom 3D LUT. I was not referring to the output format of the channels.

So again, do your team use a custom LUT like ACES, or just the standard sRGB while authoring the materials?

 

Henning

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This would depend entirely on the studio and project. If your engine uses approximate ACES, you may well want any art production viewports to use the same so as to give your artists a more accurate in game preview. Then again maybe you don't care, or you're expecting to create custom curves and etc. as you go along and so don't have a necessarily accurate way to preview it anyway.

The best thing to do really depends on your specific situation.

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Don't be confuse, srgb and tone mapping is two diferrents things and you can add a third one, color grading.

 

SRGB and REC709 ( same primaries, slighty diferrent gamma curves ) are intended to give better bit amount in the dark tones. This is because we are more sensitive there and without that curve, we would see terrible banding. Be aware that for albedo, SRGB is ok, but for light color, color gradding and fancier materials ( neon, fluorescent, ... ), if you want to support HDR and get improvement with it, you may want to edit colors in the REC2020 primaries instead.

Tone mapping is a function intended to map a signal [0..N] to [0..M] with M<N. You can think of it as compression, it is usually intended to translate from an HDR information to an LDR display. You can find many ways to do it, filmic, gloabl or local adaptation, ...

Color grading is the process of tinting your image with some logic, often artist tweaked, a common way to do it is to generate a LUT that goes from source to destination, think like the hollywood blue night filter. The tone mapping is usually include in the LUT for performance reasons.

 

Now, for artist material editing, the color grading should be off, because a material have to looks good natural under all color grading situations. BUT, the tone mapping cannot be skipped because it is a vital process in order to display the HDR image to a LDR display. You may want a tone map operator less aggressive maybe than the one in game, but it is questionable both ways.

 

It is also worth to say that the 4KUHD and windows HDR support add a whole set of new options to you, because now, we have monitors interpreting a REC2020 signal with ST2084 10bits encoding. This encoding is made to store luminance from 0nits to 10000nits, but most high end TVs don't go farther than 1000nits now. So you usually unclamp your tone map up to 700-900nits then add yourself a soft toe to the curve up to 1000-1200nits to retain control instead of letting the TV do too much tone mapping itself !

 

 

 

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On 8/14/2017 at 9:39 PM, semler said:

What I meant to write was: while creating the materials, the viewport in substance painter can show the final result

You want all your tools showing as near to your game as possible. If your game uses sRGB then you want to view substance as sRGB. Else you could get very different results from expected.

 

Keeping things constant between editors and engine will save you from adding details or needing to fix things that doesn't work in the engine.

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