Crash when rendering usd exported from SpeedTree

[peterhorvath111]

The attached usd file is exported from SpeedTree, which is a vegetation modeling software. Arnold crashes in the node initialization stage when rendering. The same usd file loads fine in Cinema 4D.

To Reproduce

• Download and unzip the attached SpeedTree_usd_error.zip
• Run kick -dp Trellis_Growth_v05.usd

Tested on Windows with Arnold 7.2.2.1 and Arnold 7.2.3.0.beta56.

[autodesk-oss-arnold-bot]

Issue synced internally to ARNOLD-13808

[cpichard]

Hi, as a first look at the scene we can see materials defined under the mesh. I am guessing the Mesh primvars are inherited in the shaders and we don't want that or at least the arnold usd procedural doesn't work well in this situation.

[cpichard]

I have reduced the issue to a simple material shading network
Trellis_Growth_v05_minimal_crash.zip

[cpichard]

Hi @peterhorvath111 ,
I found out that the crash is due to a UsdPrimvarReader shader where the varname is missing, the code was assuming that the varname is always set, as otherwise the primvar reader is not reading anything.
Do you know if the material is created by speedtree or any third party ??
Thanks

[peterhorvath111]

I believe it's created by SpeedTree. Is this something which goes against the usd specs, and should be fixed in their exporter? Or something we should handle in our code? Cinema 4D imports the file correctly, so they must handle this use-case. Here's the material, loaded in C4D:

[autodesk-oss-arnold-bot]

Issue synced internally to ARNOLD-13952

[autodesk-oss-arnold-bot]

Issue synced internally to ARNOLD-13972