USD import: investigate texture color space conversion issue #93904

@brurpo Reported the following issue:

When exporting USD from maya to blender none of the textures comes with the correct color space, they are all srgb.
Importing on maya again, on a clean scene, does not have this issue, all textures are loaded with the correct color space.
Is there a workaround for this, or is this planned?

I'll be looking into this.

Added subscribers: @brurpo, @makowalski

#97136 was marked as duplicate of this issue

@brurpo thank you for the test assets to reproduce this. I'll look into this and will let you know what I find.

@makowalski You are awesome! Let me know if you need anything, even if you want a call for me to show you the process or if you want a simpler usd.

Hi @makowalski ! Recently, maya released an update that fixed this, so it was not a problem on blenders side afterall. What was weird is that maya was importing the colorspace correctly, maybe it used something that only maya could read and now it uses something that is more generic?
If you want, I can send you the new exported USD.
Cheers.

@brurpo I'm glad there's a fix in Maya!

I tracked the issue down to the following: the colorSpace metadata in that USD is given as "Raw" (note the capitalization). Lowercase "raw" is the actual standard, I believe. In my code I was checking for "raw" as well as "RAW" (all caps) which is another variant I've seen. If I change my code to do a case-insensitive string comparison against "raw", the color space comes is correctly for this USD.

I'm guessing that Maya updated their code to use the standard "raw" token now, so we'll have to consider whether doing this fix is worth the effort. I'll give it some thought.

Added subscriber: @lichtwerk

Changed status from 'Needs Triage' to: 'Needs Developer To Reproduce'

In #93904#1269872, @makowalski wrote:
@brurpo I'm glad there's a fix in Maya!

I tracked the issue down to the following: the colorSpace metadata in that USD is given as "Raw" (note the capitalization). Lowercase "raw" is the actual standard, I believe. In my code I was checking for "raw" as well as "RAW" (all caps) which is another variant I've seen. If I change my code to do a case-insensitive string comparison against "raw", the color space comes is correctly for this USD.

I'm guessing that Maya updated their code to use the standard "raw" token now, so we'll have to consider whether doing this fix is worth the effort. I'll give it some thought.

@makowalski: I assume this can be confirmed then?
It would still be good to have an example .USD here (maybe alongside screenshots expected vs. actual behavior) just in case someone else will end up looking at this

Hi @lichtwerk. Thanks for following up on this. Yes, this bug can be confirmed, and I'll provide a USD example, as you suggested. This is a relatively simple change, and I will most likely make the fix after the latest USD Preview Surface import patch (https://developer.blender.org/D13297) has been approved and merged into master.

Changed status from 'Needs Developer To Reproduce' to: 'Confirmed'

I'm uploading the notebook.7z archive originally provided by @brurpo that contains the USDs and textures that exhibit the behavior. Note that this example is for Windows only, as it references textures in the c: drive. To test on Windows, extract the contents under the c: root for the texture paths to resolve correctly.

notebook.7z

An example of the issue is that the roughness textures in the USD

asset inputs:file = @C:/notebook/TEXTURES/ESTRUTURA_TOP/NOTEBOOK_ESTRUTURA_TOP_SG_Roughness.png@ (
                    colorSpace = "Raw"
                )

is imported with color space sRGB:

Added subscribers: @weirdmonkey2807, @mano-wii

Added subscriber: @codeloadgame

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USD import: investigate texture color space conversion issue #93904