I see! thanks for the clarification. Yes, currently physical and arnold materials don’t expose a way to toggle backface culling, while we can just read the toggle from the standard material shader.
Unfortunately, that limits us in that we now have to add some extension (like a custom property) to 3dsMax to support this feature.
While we could have a property set on a mesh that tells the babylon exporter to set double sided on all materials that this mesh uses, its a bit of an ugly solution, and I’d hate to add a feature that I want to remove later on and break people on the process
The current proposal that I like is to add a shader node to the slate editor that allows us to send per-material settings to the exporter. The only limitation is that this will take some investigation to implement properly.