Wim, I am not able to get this to happen.
I have a model in Rhino that will render, but I cant get your simple demo to show up in the render window. Perhaps you could attach the Rhino file or indicate settings. It seems so simple yet after 2hrs I am left baffled.
Ah yes I did look at that. The .gh file has a python script in it. My Python is not working right now.
Right, you don’t need the Python. Instead of the cluster that creates the geometry just add a couple of boxes or so.
Connect pieces of geometry to the top Custom Preview component, the panel with 4 material names to its material input.
To the bottom one a geometry to the geometry input and the second panel to material input
Thank you for persevering with that!
Turns out the Underscore in Wims example was the culprit.
Simplified
Rhino_Post_Changing_Materials 001.gh (44.3 KB)
Interestingly, Vray is picking up this GH geometry and will render it in the new dedicated render window if it is chosen as the render engine
It appears to render the wood material properly, but not the metal. I assume this is because this is a Rhino material not a Vray material
Even more puzzling, opening your .gh file and modifying it is no problem, but if i create a new file and paste in the custom preview module from your doc
Im guessing thats a version conflict