So I Just upgraded from rhino 4 to Rhino 5 I also upgraded the maxwell plugin to the 64 version. My problem is that I am applying material the same way I did in my previous setup of rhino 4. (I take the Materials from the database Manager to the Scene Manager under Materials then I drag and drop to the rhino layers) but when I hit the maxwell plugin render button it sends the file to maxwell but all the Materials are the rhino default gray.
Are your objects set to get their texture by layer? (In the Material options, with an object selected, there's a drop-down that offers to apply materials by Layer, Parent, or Object. You want Layer.)
Also I *think* there's an option in the Maxwell Rhino interface to render all materials as gray, but it's not set to "on" by default so I doubt that's causing it.
The Maxwell Rhino forum is excellent! Visit it here: http://maxwellrender.com/forum/ (Rhino subgroup)