Author Topic: dubcats secret little hideout  (Read 110138 times)

2018-10-01, 17:27:07
Reply #315

Juraj Talcik

  • Active Users
  • **
  • Posts: 3763
  • Tinkering away
    • View Profile
    • studio website
So who asked them for quote :- ) ? I wonder where it stands compered to much more advanced Tac7.

I really need to finish my own, it's sitting sadly half-finished against the wall for past year and half...
talcikdemovicova.com  Website and blog
be.net/jurajtalcik   Our studio Behance portfolio
Instagram   Our studio Instagram, managed by Veronika

2018-10-01, 21:07:57
Reply #316

Jpjapers

  • Active Users
  • **
  • Posts: 1221
    • View Profile
That said, I'm always wondering why we're stuck with that good old Lambertian diffuse model in corona while almost any other renderers on the market are offering more advanced one.

I keep asking Corona devs about this every three months for past three years. If we could at least get option for some existing alternative to soften up look I would be super grateful but Corona shader is super limited and not evolving in any way.

It desperately needs better diffuse shading, Coating, Sheen, etc..

It would be great to have a much more powerful shader I agree completely.

Also has there ever been a thread explaining ACES and why its better?

2018-10-02, 09:02:00
Reply #317

HVB

  • Active Users
  • **
  • Posts: 16
    • View Profile
So who asked them for quote :- ) ? I wonder where it stands compered to much more advanced Tac7.

I really need to finish my own, it's sitting sadly half-finished against the wall for past year and half...

I asked them a while ago what a Mura desktop scanner cost. And they go for $75k. So not really something for most of us.

2018-10-02, 11:03:55
Reply #318

piotrus3333

  • Active Users
  • **
  • Posts: 18
    • View Profile
Also has there ever been a thread explaining ACES and why its better?
aces’ purpose is to help film industry to manage their color input. imagine the number of image capture hardware used, all with different ways of representing captured scenes. than try matching footage from 5d, iphone, red dragon and vfx on top of it. aces makes it easy.
we have it easy from start - most renderers that we use output basicaly the same stuff: hdr color defined by rgb primaries, usualy in a form of half float exr.
long time ago Vlado posted on chaos group forums regarding rendering in aces colorspace. and if I remember correctly you should be able to switch to aces in VRayNext. not sure if it’s there yet though.

2018-10-02, 14:06:29
Reply #319

Fluss

  • Active Users
  • **
  • Posts: 437
    • View Profile
aces’ purpose is to help film industry to manage their color input. imagine the number of image capture hardware used, all with different ways of representing captured scenes. than try matching footage from 5d, iphone, red dragon and vfx on top of it. aces makes it easy.

That's true but only one side of the coin. As it's a scene referred workflow, it also allows you to preserve the whole dynamic range of your data all along the pipeline. What's more, the way RRT/ODT handles colorspace conversion gives results way closer to a film response. That's what really matters for us. You should watch this video which shows convincing results :

we have it easy from start - most renderers that we use output basicaly the same stuff: hdr color defined by rgb sRGB primaries, usualy in a form of half float exr.
long time ago Vlado posted on chaos group forums regarding rendering in aces colorspace. and if I remember correctly you should be able to switch to aces in VRayNext. not sure if it’s there yet though.

For a proper ACEScg workflow, you need to pre-convert your color textures and lights to ACEScg colorspace(D60 illuminant). The only issue is that most renderers rely on the 3D software color management which is, most of the time, based on sRGB color space (D65 illuminant). As far as I know, only maya is color managed atm.

Vray next allows you to convert your textures and colors on the fly with an OCIO node. From what I understand, it does not needs any internal changes for the renderer to handle ACEScg data. Indeed, ACES is a linear-encoded color space and as far as you feed the renderer (performing linear operations) with linear data and as far as you're outputting these linear data in a linear file format (exr), everything should work as intended and you should be able to work in ACEScg in your comp software. Renderers should be color space agnostic in that way. But we are not able to convert anything related to color temperatures  (sun, skies, lights set by illuminant etc..). That's the only blocker I can see. So if we avoid using these components, I guess we should be able to work in ACEScg with corona (assuming we pre-converted all the color textures to ACEScg). Vlado said he is actually working on native ACEScg support in Vray but I have not seen anything out for now.

Disclaimer: Everything discussed here is based on MY interpretation/comprehension of the phenomenon involved and might present some inaccuracies or wrong statements.

2018-10-02, 15:07:04
Reply #320

piotrus3333

  • Active Users
  • **
  • Posts: 18
    • View Profile
What's more, the way RRT/ODT handles colorspace conversion gives results way closer to a film response.

aces will not tonemap scene referred image. you will still need to transform it for the display device.

2018-10-02, 15:50:48
Reply #321

Fluss

  • Active Users
  • **
  • Posts: 437
    • View Profile
aces will not tonemap scene referred image.

That's what RRT is meant for.

you will still need to transform it for the display device.

That's what ODT is meant for.

What do you mean?

2018-10-02, 16:06:03
Reply #322

piotrus3333

  • Active Users
  • **
  • Posts: 18
    • View Profile
I just dont see aces space as something better for rendering purpose. I was expressing my opinion as an answer to “why is it better?” question few posts ago.

2018-10-02, 16:29:34
Reply #323

Fluss

  • Active Users
  • **
  • Posts: 437
    • View Profile
I just dont see aces space as something better for rendering purpose. I was expressing my opinion as an answer to “why is it better?” question few posts ago.

No problem with that, everybody has is own opinion :-). But I'd be glad to hear some arguments then!

2018-10-02, 17:30:49
Reply #324

piotrus3333

  • Active Users
  • **
  • Posts: 18
    • View Profile
assumption1: we put our textures and lights through aces transform. all that goes to non spectral renderer that sees just different numbers (aces primaries). math of light transport is the same in both cases. output is another bunch of numbers that describe scene referred color data. transform it again so it looks good an 8 bit display. since all that started with data described by limits of rgb representation nothing new will appear here.

assumption2: since aces is wide gamut color space it can do more than any rgb space. so you can provide the rendering engine with more data if you can somehow capture it.

thats just my take on the thing. input data limit the output no matter how crazy the math in between.

2018-10-02, 19:51:27
Reply #325

Fluss

  • Active Users
  • **
  • Posts: 437
    • View Profile
assumption 1: Even if it does not make a huge difference, it has been proven that rendering in ACEScg (which is more or less similar to REC.2020) will be closer to a ground truth full spectral rendering. Anders Langland discuss the subject in this article: https://www.colour-science.org/anders-langlands/

assumption 2: just to clarify, ACES color spaces are based on the RGB color-additive model (i.e colors are encoded with R,G and B chromaticities). RGB is a color model like XYZ, HSV, LaB etc.. By RGB, you mean sRGB which is a color space. Btw, you're absolutely not limiting the output by inputting converted data from a smaller gamut color space. As the gamut is smaller, you'll have a smaller subset of possible colors, resulting in a loss of color accuracy for representing the real world data. But you're not limiting anything here.

2018-10-03, 12:19:37
Reply #326

IsmaeL

  • Active Users
  • **
  • Posts: 47
    • View Profile
Interesting stuff here as always.

About the howl ACES debate, is there any significant advantage we would get from using ACES. This all sounds very complicated and yet I don't really se a big change.

To be honest, I would much rather prefer a wider color space inside of Max. Getting a color managed 3d application like Maya or Blender, I think even Cinema is color managed (not sure).
This would help when inputting real life colors and if we are talking about REC 2020, we could use that color space directly to work in and output images.

The second question is about the ACES compression dubcat uses, I know I read an article years ago about it. Is it somehow related to the ACEScg workflow?? Can we use it independent?? And why should we use it at all?

Finally, what is up with Lambert model for diffuse?? What is Vray using? And how would a different model be better??

BTW. Love that Canon EOS LUT
Falling in love with Corona

2018-10-03, 13:03:45
Reply #327

Juraj Talcik

  • Active Users
  • **
  • Posts: 3763
  • Tinkering away
    • View Profile
    • studio website
One idea behind asking for ACES was that it would be one fly swatted together to get both color management and some VFX utility. (And easy way to use their nice filmic tonemapper in correct way).

Corona is already using wide-gamut for internal computation but both input and output are limited to sRGB and yet unmanaged.
3dsMax is not getting color management any soon it seems (unlike Maya), so at least Corona should step up.

Vray uses Lambert by default but gives you option to mix it with Oren-Nayar (it's hidden behind the "diffuse roughness" setting). Issue with lambert is that nothing really looks like it and it's not flexible to adjust in any way (unlike other models).
Simulating rough paint for example with CoronaMTL is currently done by the fresnel mixing GGX specular over Lambert diffuse. It doesn't mesh, it's not giving correct life-like result.
talcikdemovicova.com  Website and blog
be.net/jurajtalcik   Our studio Behance portfolio
Instagram   Our studio Instagram, managed by Veronika

2018-10-03, 15:54:20
Reply #328

IsmaeL

  • Active Users
  • **
  • Posts: 47
    • View Profile
Thanks Juraj, that clears things up.

So most of this could be resolved by getting a new VFB inside Corona.
One that does correct Filmic tonemapping and where you could preview an image in a certain color space.

Basically what you can already do in Vray when you load the ICC profile of your monitor.

As for Max, you have to request the color management and maybe we get lucky. Here is the link https://forums.autodesk.com/t5/3ds-max-ideas/implement-color-management-in-3ds-max-support-for-icc-luts-etc/idi-p/6790724

As for Lambert, I guess you should just stick to shiny surfaces XD
Falling in love with Corona

2018-10-03, 16:33:05
Reply #329

Basshunter

  • Active Users
  • **
  • Posts: 23
    • View Profile
As it's a scene referred workflow, it also allows you to preserve the whole dynamic range of your data all along the pipeline.

Would you mind to further explain the sentences "it's scene referred workflow" and "it allows to preserve the whole dynamic range of your data all along the pipeline"?
I have troubles understanding some technical expressions in English.