Material Mapping preview

Discrepancies between Rhino materials and Vray materials.

I’m having some trouble figuring out how to view materials in the Rhino rendered preview window. Materials that are assigned by Rhino look absolutely fine in the preview window, but when I assign a material to an object/layer with Vray, the preview window in Rhino just shows the texture mapping preview and then long abstract lines on the rest of the object.

See attached image - the brick and glass texture assigned in Rhino are previewing as expected, but the grass on the ground plane that is assigned through Vray is on showing the material preview in a small square, corresponding to the texture mapping.

I am sure that I have fixed this before, but I can’t figure out why it’s not working with my current model. If anyone can point me in the right direction it would be greatly appreciated!!