Is it possible to get more debugging information from the Maya "vrend" command?

[vanpixelguy]

Hello,
I'm using V-Ray 4.04.02 and am launching the "vrend" command from within a mayapy session on a farm worker machine and the command fails with the message:

RuntimeError: Error occurred during execution of MEL script

I set vraySettings.sys_message_level to "4" in my scene and I do see some "debug" messages from vrend but nothing indicative of the problem. I also looked at the vray4maya_log.txt file and it is not being updated.

mayapy> vrend -camera camera:cameraNodeShape -layer defaultRenderLayer -vraySettingsNode vraySettings_xgenCacheExport -exportXgenCache 1 -exportSpecific "fred:hairGrowth1_DESC";
V-Ray: Starting render
[2020/Jan/14|17:39:21] V-Ray: Exporting scene to V-Ray.
[2020/Jan/14|17:39:21] V-Ray debug: No image file name specified; using scene name
[2020/Jan/14|17:39:21] V-Ray debug: Using image file prefix "scene_filename"
[2020/Jan/14|17:39:21] V-Ray debug: NDAG: 0
[2020/Jan/14|17:39:22] V-Ray debug: Exporting scene geometry and materials.
[2020/Jan/14|17:39:22] V-Ray: Translating selection for V-Ray
[2020/Jan/14|17:39:23] V-Ray error: There was a fatal error building the scene for V-Ray.
[2020/Jan/14|17:39:23] V-Ray: Clearing exporter memory...
[2020/Jan/14|17:39:23] V-Ray: Total time clearing exporter memory 0h 0m 0.0s (0.0 s)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
mel.eval(cmd)
RuntimeError: Error occurred during execution of MEL script

Any suggestions as to how I can increase the level of debugging information?

[moshev]

Hello,

Unfortunately it is not possible to get more debugging info, because that's all that Maya gives us, and at the point where the exception reaches us we don't have access to the python stack that caused it and can only print what you see.

However, I have a pretty good idea where it may be happening. Given that you're using XGen, it seems you may be using the old vrscene XGen renderer rather than the new (since 2015) vray renderer. For Maya 2014.5 we only had rudimentary support for XGen that worked by exporting a vrscene and later importing it - in the XGen Window, under Preview/Output you could select "vrscene" as your renderer. This has been deprecated for several years and I think you're hitting a bug in the old code. Can you go through your XGen descriptions and see if you have set "vrscene" as your renderer rather than "vray"? If vray is not showing up, make sure you have loaded the "xgenVRay.py" plugin, then in the XGen window, change the operation from Render to anything else and back to Render, after which you should have "vray" as a renderer.

Hope this helps.