Chaos Corona Forum
Chaos Corona for 3ds Max => [Max] General Discussion => Topic started by: JViz on 2020-01-14, 12:01:14
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Mod: this thread has been extracted from the V6 daily builds discussion thread - https://forum.corona-renderer.com/index.php?topic=26829.0
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just imagine how scenes will look now that the plastic feel of the materials will be gone very SOON forever
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just imagine how scenes will look now that the plastic feel of the materials will be gone very SOON forever
Why do you think so? There is fundamentally nothing wrong with current GGX behavior, it's been fixed long time ago. The different energy conservation loss illustrated above only applies to metals.
The PBR will bring new conveniences like Metalness workflow, coating,etc.. and hopefully Sheen for fabrics, but otherwise all materials will look exactly the same.
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just imagine how scenes will look now that the plastic feel of the materials will be gone very SOON forever
Why do you think so? There is fundamentally nothing wrong with current GGX behavior, it's been fixed long time ago. The different energy conservation loss illustrated above only applies to metals.
The PBR will bring new conveniences like Metalness workflow, coating,etc.. and hopefully Sheen for fabrics, but otherwise all materials will look exactly the same.
How so Juraj ? How the engine tells if a material is metal or not ? If you are not using any maps the difference between metals and nonmetalics is IOR. Then if want it to be glossy or not you adjust the parameter.
There is something off imho with current energy conservation in general material. When testing a dark interior painted all graphite with both Corona and Fstorm I'm under an impression that although both are dark the one in Corona appears more gloomy and darker in the corners etc. just as the Fstorm one would use some kind of white GI override to all materials.
Not sure if that has something to do with tone mapping or color space or whatever the reason. I'm by no means as technical as you or Dubcat or Fluss are so I'm just guessing here.
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That will 90perc. be related to GI (particularly clamping) and Tonemapping.
But also... F-Storm doesn't have correct glossiness curve, in fact it's wrong. It can make nice looking materials, but the are absolutely not PBR :- ). Ask Johannes or Daniel, they would love to change this.
So if you're asking for even more tweaked GGX behavior, it will look just slightly bit more advanced than what Corona currently has (maybe 5perc. difference?) but absolutely not like F-Storm material.
Corona's PBR will bring different UI and parameters. It will make a creation of materials easier and more like current industry standard.
They will look absolutely the same though (with exception of Sheen parameter for fabrics). Unless they change fundamentally something under the hood for BRDF, which they could...like Lambert Diffuse is getting pretty old.
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That will 90perc. be related to GI (particularly clamping) and Tonemapping.
But also... F-Storm doesn't have correct glossiness curve, in fact it's wrong. It can make nice looking materials, but the are absolutely not PBR :- ). Ask Johannes or Daniel, they would love to change this.
So if you're asking for even more tweaked GGX behavior, it will look just slightly bit more advanced than what Corona currently has (maybe 5perc. difference?) but absolutely not like F-Storm material.
Corona's PBR will bring different UI and parameters. It will make a creation of materials easier and more like current industry standard.
They will look absolutely the same though (with exception of Sheen parameter for fabrics). Unless they change fundamentally something under the hood for BRDF, which they could...like Lambert Diffuse is getting pretty old.
Yeah thought so that it might have something to do with Tonemapping and GI. Increasing Max ray depth and sample intensity does not affect the behaviour I'm referring to - it does not make the interior considerably brighter. Changing all materials to whites/white'ish grey overrides on the other hand does. That was the reason why I requested a simple "white override" checkbox in CoronaMtl. And why I asked if Devs are monitoring Dubcats thread quoting the energy conservation thingy.
And I know that white reflects more or the light spectrum than black does, so probably gloomy corners are more or less correct. But something seems off and I can't narrow it down to a single thing.
All in all I think that there is a general consensus that people would love to see Tonemapping and material (including the things you mention) overhaul.
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Everyone would :- ) I asked for both almost 4 years ago.
But some people expect miracles...and there won't be any miracles.
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I'm curious to see the impact of multiple scattering in interiors tho! Not sure this would have a tremendous impact but we can't conclude anything without testing it.
The different energy conservation loss illustrated above only applies to metals.
What makes you think that? It applies to every single material actually. Current BRDF only account for a single bounce of light. With High roughness, this causes a significant energy loss (up to 60%). This is particularly visible on metals because their reflectance is full specular but it applies to everything. It's also pretty significant in rough transmissive materials.
Single vs multiple scattering :
(https://google.github.io/filament/images/diagram_single_vs_multi_scatter.png)
The Heitz full evaluation method involves a massive overhead but recent works from sony image work and ILM approximate the effect quite well and are way cheaper to compute (ILM method is included in unity HDRP pipeline and in google filament, so really cheap but comes with some hiccups, good for real-time only). I submitted the ImageWorks's method (based on the Kelemen-Szirmay-Kalos model) to Vlado on the chaos group forum and he was pretty enthusiastic about it.
So we basically need the Autodesk Standard Surface ( https://autodesk.github.io/standard-surface/ ) + multiple scattering approximation and we would end up with an insane shader.
For those who want to read more about the subject, Stephen hill made a great article series analyzing Imageworks’ multiple-scattering approximation :
part 1: https://blog.selfshadow.com/2018/05/13/multi-faceted-part-1/
part 2: https://blog.selfshadow.com/2018/06/04/multi-faceted-part-2/
part 3: https://blog.selfshadow.com/2018/08/05/multi-faceted-part-3/
part 4: https://blog.selfshadow.com/2019/03/30/multi-faceted-part-4/
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I'm also interested in the multiple scattering stuff. I often have to deal with metals and need them to look really good. In high contrast situations metals are quite finicky to get right, and of course the artist is part of the problem/solution so not sure if it's the current implementation or a wrong approach on my side.
Then again, I know from image reference that metals *do* react differently than what I get sometimes and I tend to think multiple scattering is a vital part. For example, a metal shader looks good in one lighting situation but needs a lot of tweaking in another which doesn't make sense sometimes, especially with glossiness values at 0.5-0.7 I have to tweak a lot depending on the lighting angle already... hmm would certainly love to see how much multiple scattering could help here.
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Really glad you joined the place Fluss. I really do believe that since the new material is being developed it should be as up to date tech-vise as possible so we wont wait for or ask for another overhaul in a year or so.
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Very interesting reads indeed, i found the google way of doing things : https://google.github.io/filament/Filament.html#materialsystem/improvingthebrdfs/energylossinspecularreflectance Super interesting , but i dont understand at least 95% of it :P
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This is particularly visible on metals because their reflectance is full specular but it applies to everything
That's all I meant exactly :- ). I only answered the critique that new PBR ( which isn't promised to come with new BRDF !) material will solve materials looking "plastic".
The energy loss issue is currently only trouble for Metals, and still fixable.
Don't get me wrong, I would love new BRDFs implemented, esp. for Diffuse shading. But our current GGX doesn't make materials look plastic any more than any other GGX implementation elsewhere and particularly F-Storm, has worse (their gloss doesn't go below 0.4 on linear scale).
The new PBR shader will mainly reorganize UI to comply with industry standard by introducing Metalness workflow instead of Intensity&Gloss only, and adding Coat & Sheen parameters. Our leather material will still look like it does right now.
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I'm curious to see the impact of multiple scattering in interiors tho! Not sure this would have a tremendous impact but we can't conclude anything without testing it.
The different energy conservation loss illustrated above only applies to metals.
What makes you think that? It applies to every single material actually. Current BRDF only account for a single bounce of light. With High roughness, this causes a significant energy loss (up to 60%). This is particularly visible on metals because their reflectance is full specular but it applies to everything. It's also pretty significant in rough transmissive materials.
Single vs multiple scattering :
(https://google.github.io/filament/images/diagram_single_vs_multi_scatter.png)
The Heitz full evaluation method involves a massive overhead but recent works from sony image work and ILM approximate the effect quite well and are way cheaper to compute (ILM method is included in unity HDRP pipeline and in google filament, so really cheap but comes with some hiccups, good for real-time only). I submitted the ImageWorks's method (based on the Kelemen-Szirmay-Kalos model) to Vlado on the chaos group forum and he was pretty enthusiastic about it.
So we basically need the Autodesk Standard Surface ( https://autodesk.github.io/standard-surface/ ) + multiple scattering approximation and we would end up with an insane shader.
For those who want to read more about the subject, Stephen hill made a great article series analyzing Imageworks’ multiple-scattering approximation :
part 1: https://blog.selfshadow.com/2018/05/13/multi-faceted-part-1/
part 2: https://blog.selfshadow.com/2018/06/04/multi-faceted-part-2/
part 3: https://blog.selfshadow.com/2018/08/05/multi-faceted-part-3/
part 4: https://blog.selfshadow.com/2019/03/30/multi-faceted-part-4/
great links indeed. how does the new Advanced diffuse model change things for the corona material?
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Look at the first changelog entry of the new arnold 6.0 release : https://docs.arnoldrenderer.com/display/A5ARP/6.0.1.0
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Does this affect the amount of light transfered after the first bounce, or only the material itself ? In other words will the entire scene using this model get brighter ?
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Look at the first changelog entry of the new arnold 6.0 release : https://docs.arnoldrenderer.com/display/A5ARP/6.0.1.0
yep yep yep. awesome stuff! is the new corona diffuse model gonna implement Oren-Nayar reflectance model, like the Oren-Nayar roughness parameter in Arnold, which should remove the darkening effect Lambert creates at grazing angles which in fact result in the plastic look? if yes then that would be a great step forward for corona material.
examples
(https://cdna.artstation.com/p/assets/images/images/020/360/812/original/brian-leleux-concrete.gif?1567489016)
(https://cdna.artstation.com/p/assets/images/images/020/360/814/original/brian-leleux-mud.gif?1567489018)
(https://cdnb.artstation.com/p/assets/images/images/020/360/811/original/brian-leleux-brick.gif?1567489014)
(https://cdnb.artstation.com/p/assets/images/images/020/361/005/large/brian-leleux-overview.jpg?1567490450)
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Wow, the Oren-nayar looks so much better!
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Wow, the Oren-nayar looks so much better!
Sorry, i don't get it... In my opinion / habits, Lambertian looks better here...
Can you explain why i'm wrong ?
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Wow, the Oren-nayar looks so much better!
Sorry, i don't get it... In my opinion / habits, Lambertian looks better here...
Can you explain why i'm wrong ?
What do you want me to explain ? I staded my subjective opinion, you stated yours. IMHO oren-nayar looks way less plastic - obviously visible in the mud exaple.
Looks also more convincint at grazing angles. Sort of like the lambertian model had kind of a black halo on 0 angle.
Hard to tell the real difference without proper testing in various conditions tho.
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Oren Nayar is perfect for rough, dirty, dusty, non-shiny surfaces - mud, soil, stucco walls, concrete, rubber etc. It's something you can see when you look at the moon - it doesn't look round, it looks almost flat, because of the rough surface. Oren Nayar is quite old though, I believe there are newer, better shading models available now. Still, it would be great to have anything that helps with these surfaces.
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The most recent PBR shaders also adjusted roughness of diffuse BRDF automatically with specular BRDF.
So not like old Vray shader where Diffuse Roughness simply interpolated between Lambert (default 0) and Oren (1), and enabled monstrosities like fully rough diffuse + fully specular GGX response on top :- ).
Instead, setting the general roughness parameter to 0.4 example would adjust both BRDF of the diffuse and the specular part.
This sort of approach, not giving user the option to created artificial crap is the right way to go.
But I also believe simply adopting Oren-Nayar would be half solution at this time. There must be something new, better, more universal. The difference between Lamber and Oren-Nayar is too radical even when interpolated in-between.
But it's still better than having only Lambert.
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I'm a little dubitative while looking at the results shown above. I wouldn't expect that much of an impact from oren-nayar alone. Those are marmoset toolbag renders right?
The old Vray model was not even oren-nayar, it's a custom gamma-based model that looks like.... em... Oren-nayar is way better ! I wouldn't even consider the Disney one. Even if they manage to get the same roughness as GGX, it is not energy conservative...
The only issue is that Oren-nayar and GGX roughness don't match and as far as I know, there is no good conversion between those two. Some attempts have been made in the real-time space, but it does come with trades-off.
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Wow, the Oren-nayar looks so much better!
On my opinion Lambertian is much better
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I'm a little dubitative while looking at the results shown above. I wouldn't expect that much of an impact from oren-nayar alone. Those are marmoset toolbag renders right?
The old Vray model was not even oren-nayar, it's a custom gamma-based model that looks like.... em... Oren-nayar is way better ! I wouldn't even consider the Disney one. Even if they manage to get the same roughness as GGX, it is not energy conservative...
The only issue is that Oren-nayar and GGX roughness don't match and as far as I know, there is no good conversion between those two. Some attempts have been made in the real-time space, but it does come with trades-off.
yes exactly, these at best are artistic pseudo-mathematical representations of Oren-Nayar, any google images search for Oren-Nayar would give many images comparing Oren-Nayar's implementation with physical models and then Lambert, it's very clear Oren-Nayar is closer to reality. if somebody doesn't like how a shader looks if it's closer to reality I think it's very clear where the problem is!
I admire your insight Fluss, I think we are at a point where theory is experiencing a schism, one side applies to glossy materials while the other applies to rough materials. this is not pretty. a pure shader is out of reach for now, the best we can hope for is a blend that will break at many instances. unify the forces!! lol the theory of everything anyone?
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Can't we adapt the way Arnold handles things ?
https://answers.arnoldrenderer.com/questions/2521/lambert-oren-nayar.html
Everyone would be happy being able to choose pure lambert, pure oren-nayar and anything in between.
My point asking about the shader development on the topic here was to start some sort of discussion with the Devs as to what people expect and that those more tech-guys could toss some knowledge that could be easily overlooked.
Can we hear the Dev side please ? What are you guys planning to include in the new shader ?
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Can't we adapt the way Arnold handles things ?
https://answers.arnoldrenderer.com/questions/2521/lambert-oren-nayar.html
Everyone would be happy being able to choose pure lambert, pure oren-nayar and anything in between.
My point asking about the shader development on the topic here was to start some sort of discussion with the Devs as to what people expect and that those more tech-guys could toss some knowledge that could be easily overlooked.
Can we hear the Dev side please ? What are you guys planning to include in the new shader ?
the Trello page says Clear Coat, Sheen, and Advanced diffuse model.
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Can't we adapt the way Arnold handles things ?
https://answers.arnoldrenderer.com/questions/2521/lambert-oren-nayar.html
Everyone would be happy being able to choose pure lambert, pure oren-nayar and anything in between.
My point asking about the shader development on the topic here was to start some sort of discussion with the Devs as to what people expect and that those more tech-guys could toss some knowledge that could be easily overlooked.
Can we hear the Dev side please ? What are you guys planning to include in the new shader ?
the Trello page says Clear Coat, Sheen, and Advanced diffuse model.
Are you a part of the development team JViz ;) ? I am familiar with trello roadmap. Advanced diffuse model can be interpreted in various ways.
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I admire your insight Fluss, I think we are at a point where theory is experiencing a schism, one side applies to glossy materials while the other applies to rough materials. this is not pretty. a pure shader is out of reach, for now, the best we can hope for is a blend that will break at many instances. unify the forces!! lol the theory of everything anyone?
Well, there is really nothing to admire here, just sharing stuff I read and liked. Some will share the same point of view, others won't and it's totally fine that way. But you are right if the shader is being rewritten, it should integrate the last advances in the field. And once the hype around the Disney shader as fallen a bit (I was there too), I have to admit that it's not the best one to look at for the aforementioned reasons ( it's principled but not technically phisically accurate).
(https://forum.corona-renderer.com/index.php?action=dlattach;topic=26829.0;attach=118995;image)
In that regard, the Arnold Autodesk standard surface is way better. The diffuse model is good, the sheen is way better (physically based ->http://www.aconty.com/pdf/s2017_pbs_imageworks_sheen.pdf , not like Disney one) and it has everything we need (additional specular lobe, thin-walled surfaces for both diffuse and specular, thin film etc...).
What's more it is shared as a standard for material exchange, OSL and materialX available here: https://github.com/Autodesk/standard-surface/tree/master/reference.
add to that :
_ multiple scattering for every micro-faceted lobes (links some posts above)
_ real Shadow terminator Fix (micro-facets based shadowing function) -> https://link.springer.com/content/pdf/10.1007%2F978-1-4842-4427-2_12.pdf
_ micro-facets based normal maps -> https://cg.ivd.kit.edu/publications/2017/normalmaps/normalmap.pdf
_ same for bump maps ("bump to roughness")
and you get a pretty solid shader.
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Can't we adapt the way Arnold handles things ?
https://answers.arnoldrenderer.com/questions/2521/lambert-oren-nayar.html
Everyone would be happy being able to choose pure lambert, pure oren-nayar and anything in between.
My point asking about the shader development on the topic here was to start some sort of discussion with the Devs as to what people expect and that those more tech-guys could toss some knowledge that could be easily overlooked.
Can we hear the Dev side please ? What are you guys planning to include in the new shader ?
the Trello page says Clear Coat, Sheen, and Advanced diffuse model.
Are you a part of the development team JViz ;) ? I am familiar with trello roadmap. Advanced diffuse model can be interpreted in various ways.
I'm not part of the development team, should I therefore sh**up? ;) cheers bro
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I admire your insight Fluss, I think we are at a point where theory is experiencing a schism, one side applies to glossy materials while the other applies to rough materials. this is not pretty. a pure shader is out of reach, for now, the best we can hope for is a blend that will break at many instances. unify the forces!! lol the theory of everything anyone?
Well, there is really nothing to admire here, just sharing stuff I read and liked. Some will share the same point of view, others won't and it's totally fine that way. But you are right if the shader is being rewritten, it should integrate the last advances in the field. And once the hype around the Disney shader as fallen a bit (I was there too), I have to admit that it's not the best one to look at for the aforementioned reasons ( it's principled but not technically phisically accurate).
(https://forum.corona-renderer.com/index.php?action=dlattach;topic=26829.0;attach=118995;image)
In that regard, the Arnold Autodesk standard surface is way better. The diffuse model is good, the sheen is way better (physically based ->http://www.aconty.com/pdf/s2017_pbs_imageworks_sheen.pdf , not like Disney one) and it has everything we need (additional specular lobe, thin-walled surfaces for both diffuse and specular, thin film etc...).
What's more it is shared as a standard for material exchange, OSL and materialX available here: https://github.com/Autodesk/standard-surface/tree/master/reference.
add to that :
_ multiple scattering for every micro-faceted lobes (links some posts above)
_ real Shadow terminator Fix (micro-facets based shadowing function) -> https://link.springer.com/content/pdf/10.1007%2F978-1-4842-4427-2_12.pdf
_ micro-facets based normal maps -> https://cg.ivd.kit.edu/publications/2017/normalmaps/normalmap.pdf
_ same for bump maps ("bump to roughness")
and you get a pretty solid shader.
thanks for the links Fluss! I'll make sure to go through it all, Arnold's shader is quite solid it seems. the dev team is not being very transparent so far and that's understandable because it's very probable that they don't yet know what they can achieve within the time frame of V6 release.
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(https://pbs.twimg.com/media/EVO2byMU0AAv1pc?format=jpg&name=large)
Looks like things starts to move, Clarisse will embed the Autodesk standard surface shader and now otoy is doing so.
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@Fluss,
Heh, I was watching that presentation as soon it went live. Otoy has been rolling lately imho :) One thing to add to the above, they also plan on implementing a Multi Scatter GGX BRDF. I doubt it will be in 2020.2 because Jules did put it into "we are working on it" list but yeah, super great to hear!
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Agree, they really raised the bar lately.. I'm especially impressed by the decentralized render farm. I wasn't expecting them to launch it so quickly. I was watching the advances of golem cryptocurrency but I have to admit that RNDR looks far more solid, especially with the announcement of Autodesk joining the train.
Also, that render on IPhone GPU is impressive ! Can't see any usage for this but tech wise it' pretty cool
(https://forum.corona-renderer.com/index.php?action=dlattach;topic=27739.0;attach=123790;image)
Also, it's color managed, so you can work in ACES. I still can't believe 3ds max still isn't implementing color management.. Especially considering Autodesk has one of the ACES implementations with Maya Syncolor (not LUT used, pure CTL code).
And yep, Multi Scatter GGX BRDF is adopted everywhere... Arnold, Clarisse, Octane, 3Delight, etc etc... Things go fast
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Heh, yep, I mean subjectively I think 2018+ releases really got better and they stuck to their roadmaps more - I am quite happy with all they developed in the last couple of years. The roadmap moving forward also, to me at least, seems really great.
The RNDR framework is quite something. I actually gave it a go on a simpler scene and well... It worked super great. I do think they are looking into solving some issues with complex scenes and all that but my experience so far (on that one project) was stellar. The render job came back quick, it was as excepted and the previews for the project (it was an animation) all displayed properly.
I am also super fascinated with their work on Vulkan as supposedly most of Octane is actually already running on Vulkan / GLSL. I'm really intrigued as to how the ecosystem would open up once more hw vendors start getting in on it. I'm actually happy to see that the broader community is also quite interested in seeing how that develops especially since the other hardware vendors are also getting in on the RT game. I'm giving Otoy major props for pushing in that direction.
As for the thing being ACES color managed - There is still no OCIO but you can export in ACES. So basically in my opinion its still not production ready from the ACES standpoint but I think they've mentioned a couple of times that its going to get gradually better. I think, but don't hold me to it, I think they improved the color management in the standalone and added ACES exports as the first step. You also have control over sRGB / Float type of imports but that's been in there since forever.
So yeah, I mean I'm really excited about what they are doing. It goes without saying, I'm also excited to see what the Corona folks have going in the CPU front. :P
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As for the thing being ACES color managed - There is still no OCIO but you can export in ACES. So basically in my opinion its still not production ready from the ACES standpoint but I think they've mentioned a couple of times that its going to get gradually better. I think, but don't hold me to it, I think they improved the color management in the standalone and added ACES exports as the first step. You also have control over sRGB / Float type of imports but that's been in there since forever.
Hmmm, interesting, I didn't notice that. That said I suppose it's handled a bit differently as it's a spectral renderer. There shouldn't be the need for pre-converting to ACEScg as it is already translating everything to spectral data (I assume it's XYZ). So the transform is probably translating XYZ to ACEScg.
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Yeah, I know nothing about how a spectral renderer does things :)) I barely know how RGB renderers work so that adds another level of complexion that is honestly way beyond me...
If you've went through the GTC talk by Jules then you'll see that they plan on adding OCIO support which would then probably enable you importing ACES corrected textures as well as viewing the image with the ACES transforms. That's pretty much all I know, ha! :)
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Am i understanding correctly that autodesk are looking to implement an industry standard material definition?
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Am i understanding correctly that autodesk are looking to implement an industry standard material definition?
Yes, you can see the whitepaper here: https://autodesk.github.io/standard-surface/
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Am i understanding correctly that autodesk are looking to implement an industry standard material definition?
Yes, you can see the whitepaper here: https://autodesk.github.io/standard-surface/
This is nice to see. Hopefully a bit of interoperability will make everyones lives easier.
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And an OSL reference is available at:
https://github.com/Autodesk/standard-surface/blob/master/reference/standard_surface.osl
PS
Did a quick test and doesn't seem to work w/ appleseed, cycles, vray = crashes or outputs pitch black