As part of a learning process I'm following an instruction video designing a small house. For some reason materials aren't displayed during 3D views with shaded visual style and fine detail level. They are displayed in all other views except in 3D. But, if I render a 3D view, then the materials show up. I'm quite new to Revit, and so I don't really know my way around all the settings that might cause this. Might just be a simple thing. Any ideas?