Author Topic: dubcats secret little hideout  (Read 133153 times)

2018-11-02, 12:35:06
Reply #330

maru

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It seems that there is a kind of communication problem between the users requesting this feature, and the developers. We'll be sure to sort this out.
On the other hand, there are some strong arguments why this should not be implemented (or at least not in a way users seem to be expecting it). I do not want to sound too mysterious, but we will have to come up with a clear explanation, and only then share it.
Sorry that this is taking so long.

2018-11-02, 19:14:16
Reply #331

Fluss

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It seems that there is a kind of communication problem between the users requesting this feature, and the developers. We'll be sure to sort this out.
On the other hand, there are some strong arguments why this should not be implemented (or at least not in a way users seem to be expecting it). I do not want to sound too mysterious, but we will have to come up with a clear explanation, and only then share it.
Sorry that this is taking so long.

Half off-topic : would be nice to have a way to export true RAW linear renders with Corona. Bypassing the internal Corona tonemapping. It seems impossible to have a pure RAW Render. Not bad actually, it will always look more photo real, but it's nice to have something as neutral as possible to sometimes do it all in post for VFX workflow (as it is with Arnold for exemple, which has no tonemapping at all but has OCIO/Lut support).

Octane has a beautiful tonemapping, but there is a checkbox to render without it for neutral linear raw EXR.

Actually, you can. Just leave parameters to default and save it as exr 16 or 32 bits float.

2018-11-02, 21:27:25
Reply #332

PROH

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1 - There is a checkbox in VFB
2 - There is a Beaty RE with a checkbox

Do you need more checkboxes?

2018-11-04, 14:37:18
Reply #333

Juraj

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I'm as confused as dubcat sometimes...

Dubcat for sure as hell isn't confused lol, what are you on about with the past five or so posts :- D.

Tonemapping will be reworked by offering more advanced algorithm behind it. The UI is already as transparent as it will get, the checkboxes for everything are there.

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2018-11-12, 04:41:53
Reply #334

mh

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Here's the first public "Roughness to IOR" LUT test.

Since slate and LUTs are a complete gamma mess, I have embedded all the gamma conversion stuff inside the LUT.


Hi dubcat

This is great! I've been playing with this for the past couple of days and the IOR map works flawlessly! The added detail is astounding

I just want to clarify what the LUT actually does, and what IOR it produces, ie is it true that the high pass filter + LUT results in about 1.52 IOR? This seems fine for most materials but I tend to go a bit lower for plants, is there a nice way how to get the IOR down to say 1.4 and be somewhat precise about it? I could artificially color correct the node to bring the brightness down a bit but it seems contradictory to the whole setup

thanks!
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2018-11-15, 08:09:16
Reply #335

Nejc Kilar

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Here is a pretty good example of the ACES inspired tonemapping that I think Dubcat was talking about a few pages ago when he compared how F-Storm does things and how Corona does things ->


Maybe its helpful for someone in order to understand the differences :)

I was always under the impression that Octane / F-Storm use spectral rendering (basically converting RGB values to wavelengths internally) and that is what causes the colors to shift when they are bright / have high exposure. @Dubcat Do you have any idea whether those engines still do something differently internally or is it just a tonemapping technique?
« Last Edit: 2018-11-15, 09:25:47 by nkilar »

2018-11-15, 12:32:16
Reply #336

Fluss

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I was always under the impression that Octane / F-Storm use spectral rendering (basically converting RGB values to wavelengths internally) and that is what causes the colors to shift when they are bright / have high exposure. @Dubcat Do you have any idea whether those engines still do something differently internally or is it just a tonemapping technique?

I'm pretty convinced that Fstorm/Octane does not use spectral rendering except for specific tasks like dispersion (which is the same for Corona I guess). Spectral rendering tend to produce colored noise which is not the case. I might be wrong tho.

Anyway, the highlight color shift is not related to light transport. It's just a tonemapping technique. Basically, standard sRGB display transform clip colors above 1 resulting in white color. ACES compress values by applying a curve before display adaptation. That's all it takes. I've made some test in Vray via OCIO and it works as intended.

2018-11-16, 09:51:48
Reply #337

IsmaeL

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The only problem I see with OCIO is that it is only a view transform, so you can't save the image from the VFB with transform applied. This is the annoying way Vray has of doing things.
I guess in Corona you could just save the image as is shown in the VFB or make the OCIO apply internally in some advanced option, so people don't mess with it.

What is clear to me, is that we want ACES tone mapping applied as a standard, just like in UE
Falling in love with Corona

2018-11-16, 15:52:19
Reply #338

Nejc Kilar

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The only problem I see with OCIO is that it is only a view transform, so you can't save the image from the VFB with transform applied. This is the annoying way Vray has of doing things.
I guess in Corona you could just save the image as is shown in the VFB or make the OCIO apply internally in some advanced option, so people don't mess with it.

What is clear to me, is that we want ACES tone mapping applied as a standard, just like in UE

Pretty much +1 on everything you said. The way V-Ray does things is still beyond my understanding. They offer "basic" VFB settings yet you can't even get a LUT saved out of the VFB (at least in certain cases). Why, oh why :)

@Fluss
Yeah, well I was under the impression that because they do some sort of spectral / hybrid rendering that the RGB values get converted to wavelenghts internally and so it gets that ACES OCIO effect going. I hear what you are saying though, would be interesting to dive deeper into it...

2018-12-28, 05:58:55
Reply #339

DanNissn

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@dubcat

Hey I saw your post on the importance of keeping reflection color pure white and understand the importance for keeping the Fresnel edge to pure white. Instead of using IOR maps to add this detail could you still use maps in the reflection slot remapped with a falloff map to upkeep the pure white edge?? Sorry if its a dumb question have been keeping up with all your posts for a while, love all the information and theories/ideas you provide, keep it up

2019-01-08, 13:59:34
Reply #340

Jpjapers

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Im trying to move my workplace onto an ACES workflow and i was wondering if anyone can explain if theres anything that im supposed to be doing with textures?

Also @Dubcat are you still working on the paint LRV LUT? Id be interested to see a step by step tutorial!
« Last Edit: 2019-01-09, 20:20:37 by jpjapers »

2019-01-13, 01:01:45
Reply #341

dubcat

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Hey!
I will be backtracking every post.

is it true that the high pass filter + LUT results in about 1.52 IOR?

Quixel cross specular scan real world materials and generate a roughness map based on their internal system. This result in a less contrasted version of the real specular scan with arbitrary values.
When we high pass a texture, we remove all the arbitrary values and are only left with the contrasting values. These values are universal and will work with any megascans scans. My LUT is calibrated to give you 1.5 IOR when a high passed roughness map should give you 1.5 IOR. If you apply the LUT to an asphalt scan, the base asphalt will give you 1.5 IOR. If there are any gem stones, they will get more IOR, and all the micro shadow areas will get less IOR.
In the future, I hope that render engines will fuse "PBR" and "scanned cross specular" into glossiness. Right now PBR glossiness reduce IOR at lower glossiness values, but it's global and ignore micro shadowing.
My ultimate wish right now would be to get Diffuse Roughness in Corona, and then get some kind of futuristic PBR + scanned cross specular interaction into glossiness for micro shadowing. This would not break the current PBR workflow and/or maps, but only improve them.

I could artificially color correct the node to bring the brightness down a bit but it seems contradictory to the whole setup

This would be 1000 times easier if only Corona had specular support like Unreal 4 and fStorm. We don't have to settle on IOR or Specular, we can have both. I can generate a LUT that has 1.4 IOR as base. But let's cross our fingers that Corona will get a dual setup in the future!

The only problem I see with OCIO is that it is only a view transform, so you can't save the image from the VFB with transform applied. This is the annoying way Vray has of doing things.

THIS! I beta tested this stuff last summer and everything was VFB only, everything got ignored when you saved the image. And the ACES profiles did't have the Epic Unreal 4 blue fixes, so blue turned pink.

Instead of using IOR maps to add this detail could you still use maps in the reflection slot remapped with a falloff map to upkeep the pure white edge?? Sorry if its a dumb question have been keeping up with all your posts for a while, love all the information and theories/ideas you provide, keep it up

I've never though about this situation after PBR glossiness got introduced. But when you think about it, this is something that PBR glossiness should handle. Reflection level reduces everything as Photoshop opacity, so it would reduce everything at the same %. While IOR tell the shader how much reflectivity the material should have if you are facing straight on. Corona glossiness is not linear, when you go bellow 0.6. The glossiness values are pretty much exponential from my tests.
Let's hope that I foresee the future and that glossiness and IOR will be one single map that respect micro shadowing.

This test use 0.5 Glossiness.



Im trying to move my workplace onto an ACES workflow and i was wondering if anyone can explain if theres anything that im supposed to be doing with textures?

ACES is something that is applied after the fact. That's the whole points of ACES. You can take a photo with a shity camera, render a linear CGI scene, record some video on your phone. It doesn't matter what color space or format you use, everything is converted into ACES, and everything will work in harmony when you composite.

Also @Dubcat are you still working on the paint LRV LUT? Id be interested to see a step by step tutorial!

I have a whole page dedicated to factory paints on my new site (still in beta), all the values already have IOR 1.5 factored into the value. You only have to sample the value with Corona Picker. If only I had this page 15 years ago!

edit: fixed 3 typos, I bet there are more!
« Last Edit: 2019-01-13, 02:02:22 by dubcat »
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2019-01-13, 02:09:56
Reply #342

Jpjapers

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Thanks for the insightful answers as always! I noted after i posted about the ACES texture workflow that the textures id been having issues with had incorrect gamma rather than being a grading issue!. Do you have a link to your site perhaps?

2019-01-13, 12:02:57
Reply #343

bluebox

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Hey Dubcat! I saw on trello, that the Corona Team wants to build new PBR shader. With all your immense knowledge of this stuff I think it would be great if you could participate in that proces to at least some degree. Not sure if anyone from the team follows this thread. Maybe you could reach out to the team ?

2019-01-13, 13:02:30
Reply #344

Fluss

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In the future, I hope that render engines will fuse "PBR" and "scanned cross specular" into glossiness. Right now PBR glossiness reduce IOR at lower glossiness values, but it's global and ignore micro shadowing.
My ultimate wish right now would be to get Diffuse Roughness in Corona, and then get some kind of futuristic PBR + scanned cross specular interaction into glossiness for micro shadowing. This would not break the current PBR workflow and/or maps, but only improve them.

Hey Dubcat, can you elaborate about this? I'm not sure I get it.

edit : Here is what I understand : Basically you're asking a slot to input cross polarized specular scan in order to modify the microfacets distribution, is that right?
« Last Edit: 2019-01-13, 13:16:04 by Fluss »