Hello everyone,
I recently tried the ACES Colorspace to work with it in Houdini.
Therefore I need to convert some textures and I wonder what is the correct way.

For converting textures in Nuke I do the following:
Set the Colormanagement to ACES. Import my texture, add OCIO Colorspace Node, set the input to “Utility - sRGB - Texture” and the output to “scene_linear (ACES - ACEScg)”, then render out as EXR.


For converting in Houdini I do:
Import my texture in the Comp-Network (linearize Non-Linear Images is ticked).
Then add vopcop2filter and put an OCIO transform between the in- and output RGB values.
From Space is set to “Utility - sRGB - Texture” and To Space to “ACES - ACEScg”.

But when I compare the EXR from Nuke and the Comp from Houdini I notice some distinctions.
The left image is from Nuke the right one from Houdini, as you can see Houdini-version is more saturated. I didn't do any colorcorrection for both of them.
Shouldn't they look the same?

As a side question:
Does anyone know how to reference a comp-output in an arnold skylight?
I thought i would be something like op:/img/HDRi/OUT but thats not working.
(Its working fine in a native houdini skylight though)

SiRpRoHxO
Import my texture in the Comp-Network (linearize Non-Linear Images is ticked).

Should be unticked. The OCIO transform applies the linearization. Add a convert node to convert 8bit textures to 16 or 32bit float before the transform if needed.

Not sure why the nuke one would look different since the gamma looks the same. Is the nuke write node set to write in Aces?

When linearize is unticked, it looks stranger than before. Even with a convert node in between.
(see attachment)

The Write-Node in Nuke is set to “default (scene linear)” which should be Aces, I think.
(I set up the ACES 1.0.3 Colorspace under Preferences–> Color Management)

The easiest way to do it in nuke is to change the colorspace in read node, and write to your desired colorspace, which in this case, any sRGB textures should be read as utility-sRGB-texture and write it to ACEScg, no need for any ocio node inbetween.
the colorspace knob in both read and write do the conversion for you.

but if you wish to use OCIO nodes then read your texture as Raw Data so you don't get double colorspace conversion.
Here is a nuke script that I wrote, you can just drag and drop your textures and it does the conversion to ACEScg automatically.

https://github.com/Amir-Ashkezari/RenderMan-Utility-Manager/tree/master/Nuke-script/ACEScg-Convertor [github.com]

thanks for your script, just tried it and it seems to work for me just fine.
It sets the read-node to “Utility - Linear - P3-D65” and the write-node to “Utility - Raw”.
Is that the same as the standard way “Utility - sRGB - Texture” to “ACES - ACEScg”?
(I'm not into colorspaces )

If you are dealing with 8-bit sRGB then the read node should be set utility-sRGB-texture and write set to ACEScg, but if you are trying to convert half-float/float hdri then read node should be utility-linear-sRGB and write to ACEScg.
not sure why you are getting `It sets the read-node to “Utility - Linear - P3-D65” and the write-node to “Utility - Raw”.`