I am creating some animations and short movies in ArcScene showing how a number of disparate datasets relate to one another. In one of these movies my "big finish" is to extrude a number of polygons "negatively". In other words, I have a number of data layers stacked on one another in space (in some cases naturally as a function of z-coordinates, in some cases as a function of using a layer offset, and both where I need an exaggerated space between layers) and I want to show relationships between the different layers by using extrude to drop polygons on "upper level" layers to lower layers.
I can't get polygons to extrude below their base heights... It seems weird to me as it's possible to drop layers below their base heights using negative numbers as layer offsets. When I put negative numbers in the Extrusion Value Or Expression box in the Extrude tab in Layer Properties nothing happens.
Is there a specific expression I need to use?
Also, if negative extrusions are possible, I'd like to be able to cleanly clip the bottom of each extruded polygon to it's final intersecting surface. In other words, when the intersecting surface has texture, my extruded polygons (when I've tried extrusion "going up") the entire extent of my tops either don't sit flush with the surface or go through to the other side. I envision a "3D Extract by Mask" kind of thing.
I've seen a few non-ESRI tools that may do this stuff, but I'm limited to ArcGIS (in that I'd prefer not to have to learn a whole new software to deal with my other layers.