Chaos Corona Forum
Chaos Corona for 3ds Max => [Max] Feature Requests => [Max] Resolved Feature Requests => Topic started by: karamox on 2016-04-26, 16:26:35
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Hi, noticed corona Highlight Compress works different than Vray Color Mapping.
Let me know if i am wrong. When highlight compress is 1 - it is linear color mapping.
When highlight compress is between 1-10 it like reinhard . When color compress is above 10- it is exponential.
Problem is that corona looses much of the color in the image when using exponential mode with HC above 10, we loose contrast too. Comparing same images done in Vray and Corona, images from Vray are rich color contrasty, and from Corona - they lack saturatio, look dull and not contrasty. Can you consider my notice, do your self tests to find better color mapping than it is now, wich conserves color saturation in sky and the ground.
I made comparison. Sved From Corona Images in jpeg with HC 1 and 10. And exr file witch i color mapped in photoshop using ArionFX.
Corona h compress 1- highlight compress 1 straight from corona
1.Corona h compress 10 - highlight compress 10 srtaight from corona
PS linear reinhard burn 100proc - linear color mapping in photoshop
2.PS exponential reinhard 0 proc - exponential color mapping in photoshop
As yo notice 1 and 2 images look different. This difference is in color saturation and overall contrast. The same exist if we compare images from corona and vray.
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Hmm, surprised by this. Nonetheless Reinhard should die in either case. Did you try filmic ? So nice.
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I thik it is because of color compression when using highlight compression. And it should be redone i think. O it should be added filmic color mapping.
Can you tell me how to try filmic color mapping with photoshop? Any program does this?
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I did comparison between linear and exponential. As i know reinhard is mix of these, so 100 of reinhard is linear, and 0 percent of linear is exponential.
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There is macro for Nuke and Fusion on this forum, but I use simplified version in VFB+ . (I would welcome option for advanced as well).
Corona should have the original Reinhard macro and controls, Vlado was the one who changed it onto [0-1] range, maybe he redid something else too.
Reinhard also isn't mix of linear and exponential, that's just some Vray explanation. Reinhard is Reinhard.
It also does desaturate by design: (this is not Vray article)
https://imdoingitwrong.wordpress.com/2010/08/19/why-reinhard-desaturates-my-blacks-3/
Look how ugly this crap is:
(https://imdoingitwrong.files.wordpress.com/2010/08/simple_reinhard_rgb_ramps.png)
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Is filmic color mapping integrated in VFB + o it is needed to grab script, or something else,to put or to integrate into it? Can you describe more detailed how you do it in VFB+?
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Is filmic color mapping integrated in VFB + o it is needed to grab script, or something else,to put or to integrate into it? Can you describe more detailed how you do it in VFB+?
No it's included, it's the default tonemapping there, just simplified from full control ( shoulder, white level, toe,tc..) into Highlight compression and Shadow richness. The latter doesn't always work as expected....but compression is already much much nicer. Goodbye dullness and desaturation (which you cannot bring back in post easily, because it doesn't happen across full value spectrum)
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So in conclusion, now in corona native color mapping compression is much worse than filmic color mapping compression. And the only way to avoid dullnes and desaturation in corona is to use vfb+, until FCM will be added or replaced in Corona.
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You can always do save as unclamped linear file and do tonemapping in post (manually or using plugins like ArionFX). I used to do it but it's tedious and I like same feedback in framebuffer as final result.
Great tonemapping should be part of renderer same way it's in DSLR.
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Comparison side by side of two different color compressing methods.
1 Corona highlight compress ( compresses highlights, color, saturation) image looks dull, unsaturated, not vivid, uncontrasty
2. Corona Highlight compress set to 1, and rendered in VFB+ with filmic color mapping aplied (rich shadows 0.4 compress highlights 0.9)
If you compare those images you can see wich looks much better. Many can say that 1 image we can post process, yes, but renderer should have good color mapping and color compresion itself.
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But the first image looks more "realistic" and the second one looks more "3d".
I guess, it depends in what fields do you work and what's you final goal.
Some screen grabs from Alice in Wonderland and avatar. As you can see, they are quite desaturated.
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all those images are in shadow. thats is why they are dark, and unsaturated. Desaturation and color correction was done in postproduction, raw renders ehere different.
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I couldn't find too many examples as the screens are taken from youtube trailers. But if we start from the premise that movies are color corrected and the corona render is "raw" than I guess there isn't much point to make any kind of comparison.
But I think movies like avatar and jurassic world which have lots of 3d foliage, seem desaturated to appear more real.
Perhaps the "filmic" mode has some other advantages, but in the comparison above the one more saturated look less realistic.
This screen grab from Jurassic World is taked in the sun. Not much foliage, but you can still see the color of the trees are way less saturated (the filmic render superimposed on top).
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Official note from the headquarters before Nicholas Cage movie screenshots will be compared:
The issue will be revisited in Corona 1.5 or 1.6.
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Perhaps the "filmic" mode has some other advantages, but in the comparison above the one more saturated look less realistic.
This isn't valid comparison, the tonemapping is not meant as post-production. It is a highlight compression algorithm merely to go from linear, mathematical space. You still can do (and should do) desaturation afterwards if it's creative choice, and it will look more correct, than if the Reinhard, selectively desaturated your blacks and you would have to retrieve them. There is big difference to this.
The filmic, doesn't dictate the end look. It just corrects the faulty behavior Reinhard has.
The examples by Karamox looks more 3D ish because the vegetation has completely wrong materials to start with, this just how 3D foliage packages are setup. With overbright, oversaturated albedo values because no one knows better. PBR might exist, but Evermotion is still in 2002..
Filmic does absolutely not contribute to more CGI-sh look, it's something very decoupled from this. All it does is better simulate camera response so that we can move into our post-production from better set values. Filmic is to Reinhard what Linear workflow was to gamma incorrect workflow of pre-2000. It's not artistic/creative feature alone, it's technical.
Filmic doesn't saturate anything by default (it has 5 controls, and the 'toe' gives contrast to blacks, which, can rise saturation), by it can correctly retain. There are definitely physically wrong tonemappers like HSW which saturate highlights, but filmic isn't.
Does the world loose contrast and saturation in your eyes when you step outside :- ) ?
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Does the world loose contrast and saturation in your eyes when you step outside :- ) ?
Sometimes, according to my iphone photo and even my dslr, yes :)
But maybe the above comparison wasn't a very fair one. Equally unfair would be me posting here some photos trying to prove that yes, the world outside is desaturated. Because the truth is you can take photos to appear sometimes quite green and saturated and sometimes desaturated. It depends so much by a lot of things, like what lighting is, is the sun in front ? back ? are the trees wet ? dusty ? the white balance and so on.
But sometimes the movies, or even casual photos (with auto settings and no color correction) can be less saturated than many renders. But that has more to do with the user setup of materials.
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We will explore filmic mapping again for 1.5. I added it to https://forum.corona-renderer.com/index.php?topic=3584.msg26003#msg26003
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just testing color mapping again and comparing.
these are two pictures but color mapped differently but with the same corona highliht compression method. but results are different.
i took script for fusion from user contributions to color map 32 exr.
how can it be that with the same code i get different results. bad results from corona frame buffer ( image looks dull), and good results from fusion ( image looks very good, better than frame from corona renderer frame buffer)
so i have question. maybe there is a bug in corona highlight compress? maybe it can do the same thing as fusion does with the same script. And you can save old fixed highlight compression color mapping mode, and add filmic mapping as an addition?
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IMHO the image on the right looks far worse. Over-contrasted and over-saturated.
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it is because you got used to see dull image from corona frame buffer image for a long time. and its become normal for your eyes.
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It's also because the example features the trademark toxic colors of material albedo :- ) Otherwise the deeper contrast (here might be bit too much perhaps) is definitely more natural then the washed one from Reinhard. If I want washing over, I will simply lift shadows in post and achieve vintage effect.