UsdzExport doesn't work in Build when using IL2CPP, causes Exception (FTV-248)

When scripting backend is set to Mono, I can export USDZ fine from a Windows Desktop build (haven’t verified completeness yet, but I do get an USDZ file with geometry in it).

When the scripting backend is set to IL2CPP instead, calling ExportUsdz results in exceptions:

Registering plugins: D:/git/schreibkugel/development/Builds/usdzTest/WritingBall_Data/Plugins/share/
UnityEngine.Logger:LogFormat(LogType, String, Object[])
UnityEngine.Debug:LogFormat(String, Object[])
Unity.Formats.USD.InitUsd:Initialize()
Unity.Formats.USD.UsdzExporter:ExportUsdz(String, GameObject)
RuntimeExport:Update()
 
(Filename: C:\buildslave\unity\build\Runtime/Export/Debug/Debug.bindings.h Line: 48)

NotSupportedException: To marshal a managed method, please add an attribute named 'MonoPInvokeCallback' to the method definition. The method we're attempting to marshal is: pxr.UsdCsPINVOKE+SWIGExceptionHelper::SetPendingApplicationException
  at pxr.UsdCsPINVOKE+SWIGExceptionHelper..cctor () [0x00000] in <00000000000000000000000000000000>:0 
  at pxr.UsdCsPINVOKE..cctor () [0x00000] in <00000000000000000000000000000000>:0 
  at pxr.PlugRegistry.GetInstance () [0x00000] in <00000000000000000000000000000000>:0 
  at Unity.Formats.USD.InitUsd.Initialize () [0x00000] in <00000000000000000000000000000000>:0 
  at Unity.Formats.USD.UsdzExporter.ExportUsdz (System.String usdzFilePath, UnityEngine.GameObject root) [0x00000] in <00000000000000000000000000000000>:0 
  at RuntimeExport.Update () [0x00000] in <00000000000000000000000000000000>:0 
Rethrow as TypeInitializationException: The type initializer for 'pxr.UsdCsPINVOKE.SWIGExceptionHelper' threw an exception.
  at pxr.UsdCsPINVOKE..cctor () [0x00000] in <00000000000000000000000000000000>:0 
  at pxr.PlugRegistry.GetInstance () [0x00000] in <00000000000000000000000000000000>:0 
  at Unity.Formats.USD.InitUsd.Initialize () [0x00000] in <00000000000000000000000000000000>:0 
  at Unity.Formats.USD.UsdzExporter.ExportUsdz (System.String usdzFilePath, UnityEngine.GameObject root) [0x00000] in <00000000000000000000000000000000>:0 
  at RuntimeExport.Update () [0x00000] in <00000000000000000000000000000000>:0 
Rethrow as TypeInitializationException: The type initializer for 'pxr.UsdCsPINVOKE' threw an exception.
  at pxr.PlugRegistry.GetInstance () [0x00000] in <00000000000000000000000000000000>:0 
  at Unity.Formats.USD.InitUsd.Initialize () [0x00000] in <00000000000000000000000000000000>:0 
  at Unity.Formats.USD.UsdzExporter.ExportUsdz (System.String usdzFilePath, UnityEngine.GameObject root) [0x00000] in <00000000000000000000000000000000>:0 
  at RuntimeExport.Update () [0x00000] in <00000000000000000000000000000000>:0 
UnityEngine.Logger:LogException(Exception, Object)
UnityEngine.Debug:LogException(Exception)
Unity.Formats.USD.InitUsd:Initialize()
Unity.Formats.USD.UsdzExporter:ExportUsdz(String, GameObject)
RuntimeExport:Update()
 
(Filename: currently not available on il2cpp Line: -1)

ApplicationException: Failed to create: C:\Users\felix\AppData\Local\Temp\zc0u9qvy.z7q\test.usdc
  at USD.NET.Scene.Create (System.String filePath) [0x00000] in <00000000000000000000000000000000>:0 
  at Unity.Formats.USD.UsdzExporter.ExportUsdz (System.String usdzFilePath, UnityEngine.GameObject root) [0x00000] in <00000000000000000000000000000000>:0 
  at RuntimeExport.Update () [0x00000] in <00000000000000000000000000000000>:0 

[TautvydasZilys]

which means adding the special mono tag to that code is not immediately possible…

You don’t need to reference Unity code to fix this. Just create a private class with the same name in your assembly:

class MonoPInvokeCallbackAttribute : Attribute
{
}

[jcowles]

Reviving this – going to take another crack at it and try Tautvydas’ suggestion