Material inverted after fracturing with Blast extension

When I try to fracture a cube with an albedo map, the albedo map is applied on the interior surfaces and the outside just gets a solid color. I can’t repro this with a cube mesh created within the Create app, but I can with a cube created in Blender and exported to USD. The only property difference I noticed between the two cubes was that the Blender one was set to doubleSided=1, but changing that didn’t fix it.

Let me know if you need a better repro for this.

Hi matias.codesal, I am looking into this now and will follow-up as soon as I have some info. In the meantime, please feel free to join the Omniverse Discord community server. While our forums are for official support, our Discord is a great place to chat with the community on anything Omniverse related: https://discord.gg/XWQNJDNuaC

Cheers,
Edmar

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Hi @matias.codesal, I’m on the Blast team and would be happy to look at this for you. Would it be possible for you to send the USD/USDA file that has the issue for you so I can repro it internally? Thanks

Hi @EricArnold, thanks for the help.

Attached is a zip archive with two stages, fractured_blender.usda and fractured_omni.usda. The “blender” file started with a cube mesh created in Blender and an OmniPBR shader added in the Create app. The “omni” file started with a cube mesh created in the Create app. Repro steps are the same for both files. “blender” will fail and “omni” will succeed.

  1. Open the stage
  2. Load Blast Plugin and open Blast window.
  3. Select Cube mesh prim
  4. Click “Fracture Selected” in Blast window.
  5. Increase “Explode View Radius” to view inside/outside surfaces

I had a bit more time to look into it and it looks like it’s mangling the UVs for the “blender” file. Blast seems to be getting tripped up by the UV set being named “UVMap” instead of the default “st”. If I change it to “st” it works.

blast_repro.zip (85.5 KB)

Thanks for the files @matias.codesal! I was able to repo the issue, it is definitely because of the UV format. I’ve updated our code to handle a much wider range of formats, so this shouldn’t be an issue once we publish a new version of the extension. In the meantime you can work around it by renaming the UV attribute like you noted.

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Sounds good. Thank you, Eric!