Thanks
Here is what I understand of the issue:
A VRMat file contains XML data, which is what V-Ray 1 and 2 used to store in the SketchUp files. So what Transmutr does, is store this data in the file, and rely on V-Ray 3 updating it to its new format (JSON).
The issue is when V-Ray update the XML to JSON, it finds a discrepancy: There is a diffuse texture in the XML, but no texture in SketchUp. It choses to follow the SketchUp material, and discards the diffuse from the XML. This is what you experience with your example.
When we import the VRMat directly within V-Ray, it is handled correctly. The issue is only when V-Ray converts data already present in the file (eg written by Transmutr).
I’m not sure how to fix this. We would need to find and extract the diffuse from the VRMat file, but there are so many different combinations that it may work only for the most common cases. There are many different V-Ray material types, they can have multiple layers each with its own diffuse, etc.
In Transmutr v0.2.1, the diffuse slot will be exposed in the UI, when the material type is “VRMat”. This allows the user to set a texture that will be used for the SketchUp material. In this case, you can add the diffuse texture, and V-Ray will not see a discrepancy anymore between the SketchUp material and the VRMat. But this requires manual input.
I’ll investigate if we can automate this by extracting the diffuse from the VRMat (but like mentioned above, this may be tricky if even possible)