Drape textured polygon over hillshade

I have a textured polygon layer (forests) which I need to drape on a hillshade layer (representing relief). In ArcScene, one way to do that is to make it "floating on a custom layer" (which is a 3D hillshade). The resulting surface doesn't have shadows - it is just a plain surface with contours adjasted to relief. So in order to add some volume to the surface of the forest I have to add a transparency but it makes the whole layer look fade.

Is there any way to overcome this? Ideally, I need to get from textured polygon layer and hillshade something that looks like shadowed relief with forests on it.