fix: switch sourceColorSpace

[beersandrew]

This is an attempt to make the changes @erich666 suggests in this thread: https://academysoftwarefdn.slack.com/archives/C02TZPYMP8S/p1754431278767889

In this PR I swapped the colorspaces as specified, and rezipped. I also took screenshots in usdview but to be honest I'm not 100% that those screenshots are what we want here, and I'm not sure if there is text that's required to change in the readme as well.

@erich666 for future reference if you're interested, this is what I did

1. Unzip the USDZ -> unzip RoughnessTest.usdz (this puts the files RoughnessTest.usdc + image files in 0/ in the current directory
2. Convert USDC to USDA -> usdcat RoughnessTest.usdc -o RoughnessTest.usda
3. Edit the file
4. Convert USDA to USDC -> usdcat RoughnessTest.usda -o RoughnessTest.usdc
5. Re-zip files -> usdzip RoughnessTest.usdz RoughnessTest.usdc 0/*
6. Test -> usdview RoughnessTest.usdz

[erich666]

Thanks for the USDZ and USDC steps, especially step #5's way of including a subdirectory. Unfortunately, trying out usdcat today, some paths or something on my system are severely borked, "DLL load failed while importing _tf" and much other fun.

Aha! Checking the USDZ spec, the only image types now officially supported are: png, jpeg, exr, avif. So, that roughness.tga file needs to be a roughness.png. I've attached one for your convenience. Then change all roughness.tga to roughness.png in the USDA file, repackage, and you're done.

[beersandrew]

Unfortunately, trying out usdcat today, some paths or something on my system are severely borked, "DLL load failed while importing _tf" and much other fun.

Mine was broken too, although maybe a different error message. I had an incomplete USD build on my path. Not sure how you run USD but if you follow the python install scripts python3 build_scripts/build_usd.py /Your/desired/install/directory/here all of the tools should "just work"

[erich666]

Thanks for the USD tools advice, but in my case I'm on Windows, so have been using NVIDIA's distribution. Usdview works great, but the other tools have some sort of path problems, I think. As usual, I have about 50 python.exe files on my computer, so, good times!