(Closed) [HOU-1726] Acescg primaries mode in Houdini

[LeoYfver]

when ocio is enabled should it grey out and disable the colorspace dropdown?

[Gosho.Genchev]

No, certainly not if that's regarding the VFB. Could you share more info, e.g. Operating system / Houdini / V-Ray versions ?

Thank you!

[hsz]

Quick question when you change the color space in color mapping does this also affect the color swatches as well? Meaning that I'm pricking my colors in Aces or not? Thanks.

[bdancer]

hsz, this is a V-Ray ROP specific control - it has no effect on Houdini UI.

[hsz]

Got it, so if I have my OCIO setup config correctly set up all should be good to go. Thanks.

[docaml]

Everything is clear for me, but I have one suggestion, now, if you need to pick up exact color (logo, etc), you have to build it by two nodes, COLOR node that is plugged in OCIO node. It would be much easier if there is color picker in OCIO node directly, like this (or something like this):


So there would not be need for additional color node:


Best,
Doca

[Muhammed_Hamed]

Good suggestion!
Another problem with using a color node + OCIO node, is that we don't know the actual values that Vray is using internally. And this could be an issue, if the converted values are higher than 1
Maya has a perfect solution to that, because you can configure the OCIO file to make color picking in Out-sRGB for example .. and if you unchech "color management" option in the editor you can see the actual converted ACEScg values
It is a bummer that Houdini color editor only uses float values, would have been easier if it works like Maya's or Modo's
I guess you can convert the colors in Nuke or an online converter, which would be pain

[chakarov]

docaml , your request should be available in next nightly build.

[Hannes Drossel]

Hey, Hannes Drossel ,

those float parameters are indeed not handled, I've logged it and messaged the developer. I'll ping you once a solution is implemented.
I was hoping to be able to give you a work-around but hit a wall there as well - we'll have to add support for conversion of the color pickers. We'll try to get this working as soon as possible.

Thank you for bringing this up!

Hi!

The issue with the hair shader and acescg primaries has become a more urgent issue as we are about to start a project with a lot of hair. We want to be able to use the hair shader and acescg primaries in Houdini.
When do you think this issue will be resolved Gosho.Genchev ?

Cheers!

[Hannes Drossel]

when ocio is enabled should it grey out and disable the colorspace dropdown?

Also pushing for this request. The colorspace parameter is causing confusion when OCIO is now a part of the image file node. In my opinion the color space parameter should have no effect when OCIO is enabled on the image file node.

Cheers!

[Gosho.Genchev]

Hey, Hannes Drossel ,

I'm messaging just to say we're looking into the Hair material issue with AcesCG - I'll ping you with any info I get on this.

Also pushing for this request. The colorspace parameter is causing confusion when OCIO is now a part of the image file node. In my opinion the color space parameter should have no effect when OCIO is enabled on the image file node.

Logging it and we'll update this as soon as possible.

Best regards!

[Hannes Drossel]

Thank you Gosho.Genchev !

[Gosho.Genchev]

Hey Hannes Drossel ,

we have something now that hopefully addresses the issues you were having with the Hair material. I did my own tests - I was looking for saturation or light intensity issues, and whether the settings dialed on the shader resemble what the result should be in the VFB. To me, it seems we've managed to resolve the issue with Aces and the Hair material but if you guys could please take a look yourselves, I would be very grateful.

Tomorrow's nightly builds will contain the Hair material changes.
Those are currently in V-Ray for Houdini only - you mentioned you need it urgently so we kind of rushed it. I'm saying this so you're aware the result may differ if down the line it turns out more changes are required.

Here's how those look:



One last thing - increasing the Melanin parameter to a value over 0.7 seems to produce darker results with ACES - is that something that could be problematic for you ?


All the best!

[Hannes Drossel]

Thank you Gosho.Genchev !

I will take a look and get back to you.

Cheers!

[Hannes Drossel]

Hi Gosho.Genchev !

So I checked out the fix and it looked promising at first.
But like you say the result is darker and more high contrast than when working in srgb mode.
This could be a problem as well as what you say about the result might change with newer versions of vray as we are constantly updating to new versions.

Without knowing the internals of the shader I would imagine that the melanin/pheomelanine combo would result in some RGB values. These RGB values are then combined with other colors parameters and used as an albedo in the shading computations.

As the shader is built for an sRGB workflow the RGB values would therefore be in linear sRGB color space.
Using a matrix transformation on those RGB values would transform them into ACEScg color space.

Doing the transformation on the RGB values before any other operation (like mixing in other color values from the shader parameters) would give the proper result.

Here is a link to a color space transformation matrix generator.
https://www.colour-science.org:8010/...rmation_matrix



Here are the settings I use in Nuke for this stuff.

Like I said I dont know the insides of the shader so forgive if I'm way out of line here. Really hoping this can help in making this work.

Cheers!