Custom ACES config not working with Arnold

[am_wilkins]

Hi,

I've been trying to get some Houdini OCIO rules working with Arnold, but they appear to be ignored.
Noticed there was an recent update that I thought would fix it but it didn't.

• "OCIO environment variable priority: The OCIO environment variable now takes priority over the configuration file set in the Arnold OCIO color manager as well as the builtin OCIO configuration file. A new ignore_environment_variable parameter on the OCIO color manager causes Arnold to ignore the value of the environment variable and restores the previous behavior. The OCIO environment variable is also now taken into account by maketx. (ARNOLD-9012)"

Example texture naming:
plant_baseColor_ACEScg.1001.exr

Example Auto-TX result:
pricklyPearA_plant_baseColor_ACEScg.1001_raw.exr.tx

Makes it "_raw" but it should be in this case "_ACEScg"

As far as I can see it's all setup correctly.
Example file rules:

file_rules:
  - !<Rule> {name: ACEScg_exr, colorspace: ACEScg, pattern: "*ACEScg*", extension: exr}
  - !<Rule> {name: ACEScg_png, colorspace: ACEScg, pattern: "*ACEScg*", extension: png}
  - !<Rule> {name: ACEScg_tif, colorspace: ACEScg, pattern: "*ACEScg*", extension: tif}
  - !<Rule> {name: Raw_exr, colorspace: Raw, pattern: "*Raw*", extension: exr}
  - !<Rule> {name: Raw_png, colorspace: Raw, pattern: "*Raw*", extension: png}
  - !<Rule> {name: Raw_tif, colorspace: Raw, pattern: "*Raw*", extension: tif}
  - !<Rule> {name: srgb_texture, colorspace: sRGB - Texture, pattern: "*srgb_texture*", extension: exr}
  - !<Rule> {name: Default, colorspace: ACES2065-1}

And registered correctly in Houdini

Thanks,

amwilkins

--

Houdini Core Version 20.0.653
Arnold Core: 7.3.1.0

HotA: 6.3.1.0

CPU: AMD Ryzen TR 3990x

RAM: 128GB
GPU: NVIDIA RTX 4090
OS: Windows

[am_wilkins]

Hi there,

Any confirmations that there are issues around a custom OCIO config and HtoA?

We would really like TX files being generated in the correct space automatically without other setup on the artists side.

Karma appears to work fine with my settings above.

Thanks.

[Stephen.Blair]

Any known issues were addressed in the previous updates.

How to repro?

Set OCIO to any config, and that doesn't work in Houdini?

[am_wilkins]

Hi Stephen,

Yes, whichever OCIO config file you're using on your end—just add a rule set such as above.

Another example in the file.

Then in the new "OCIO" settings in Houdini you should see them appear in the UI.

After that, it's dropping down a texture map and letting "auto-tx" run and see what space you get.

Arnold seems to ignore the rules, so it forces setting the space on all the "image" node drop-down menus instead.

thanks,

amwilkins

[Stephen.Blair]

Does the Arnold log show that it finds your custom ocio config?

Then it's a problem with the file rules.

Will set up a repro...

[Stephen.Blair]

Looks to me (from testing and checking the code) that Arnold does not read the file_rules from the config. The host application might (like Houdini and Maya), but if the host application doesn't automatically propagate the file rules to image nodes, you have to do it yourself (set the color space on the image nodes).

[am_wilkins]

Thanks for testing!

Interesting... seems a little counter productive.

At the end of the day one would want to set these rules once and have them work hands-free in either Maya, Houdini or any other supported DCC for example. Just manage your texture file naming and you're sorted.

Could Arnold not look at the file rules when generating the TX files? That would be my request.

I thought from the last update it sounded like it would do this, but I guess this is the overall config and not specifically the file rules.
"The OCIO environment variable is also now taken into account by maketx. (ARNOLD-9012)"

Karma doesn't appear to set the rules on the image nodes (using a material X builder for example, since the spaces don't even work on that mat x image node), but just uses them from Houdini OCIO settings when generating the RAT files I believe, so doing exactly what we'd expect.

thanks,

amwilkins

[Stephen.Blair]

Every DCC is different, so we can't just read the file_rules. Users may have set something in the DCC (eg in Maya, which reads in the file rules and then lets the user modify and add rules, and those rules are then part of the Maya scene).

It will be an option, or maybe something we do only if the image.color_space parameter is in "auto" mode.

[am_wilkins]

Yes, I understand... 👍

I thought Maya used to have a "Use config file riles" checkbox, and when switched on would "Grey out" the rules section and just use what was set in the config file. Then you couldn't touch it anymore, I see that's gone though.

Houdini OCIO settings might set any new ones you add in the config automatically perhaps assuming it's a local config. I remember I was adding them there first and then checking the config to see how it's formatted.

Anyways, I think most bigger studios would want to configure the ruleset in the config and have that the driver for all dcc. Thought that was the way it was supposed to work.

"It will be an option, or maybe something we do only if the image.color_space parameter is in "auto" mode."

Yeah that makes sense. Was thinking of the same option.

all the best,

amwilkins