Add depth to rectangular mesh for surface plot visual

Hi,

I'm a bit of a newbie to 3D WPF, and am working on simulating cracks and holes dynamically on a surface.

I found your SurfacePlotDemo to be extremely useful, and was able to do this:



but would like to extend it to something like this:



The workaround I tried was using a BoxVisual3D (with the TopFace set to false) that is aligned with the surface, but this obviously doesn't render well when the hole is near the edges of the block.



While going through the SurfacePlotVisual3D class, I noticed the use of AddRectangularMesh() which creates the surface from an array of 3d points. Is there a method in MeshBuilder that can extend or add "depth" to to it as well? Or append another "cuboidal" geometry with one face and the sides to match the surface plot - this would perhaps be more ideal because I'd like the bottom half to be partially transparent in order to actually view the crack during rotation.

Any ideas or suggestions would be greatly appreciated. Thanks!