Hi,
A feature i would find useful would be where i can add a "floor" or bottom or intermediate level of a surface within the boundaries of an existing piece of geometry.
For those in my situation, in designing ships and boats, it may be common that the hull (vessel's body) is brought in from an external package, such as PolyCAD or Delftship
http://polycad.co.uk/http://www.delftship.net/In my case, i use delftship mostly, and then add stations (most naval architects might use "stations" at convenient locations in order to obtain convenient stability and buoyancy calculations, but i add stations in order to mark where my main transverse (side-to-side) bulkheads (walls/dividers). Then, I add additional stations represending the distance offset to get the thickness of the bulkhead plating.
In ViaCAD, I create surfaced around these bulkheads and then stitch them together.
For convenience, on another layer, i add in Delftship stations every foot (which bogs down the model a tiny bit, in either D/S and in ViaCAD) so that in tricky areas i can add skin surfaces and have them added based on the original model, not on black-magic misinterpretation on my part which might deviate from the original model.
To create the sideshell (skin of the ship) I use the stations that Delftship created and simply add surfaces between the plates. To add thickness to the side plating/side shell, i simply use the thicken tool and set the thickness accordingly. In reality, the thickness varies depending on classification society rules, which dictate these things based on waterline length, depth of the ship (vertical distance between the uppermost continuous deck to the keel (bottom outside the plate of the keel)), freeboard (distance between the waterline and uppermost continuous deck), draft (distance between the keel and the waterline), the beam (width at the waterline), and other things. Some plate may be allowed to be 18mm thick, while in some areas it can be no less than 32 mm thickess. So, in VC, I actually should be cutting up the model at various planes and assigning thickness according to areas needing more protection from corrosion or statistical likelihood of collision, for areas serving as tug push/pull points, areas where openings occur in the side shell, and so on.
Now, where my dreamlist idea would be useful is creating compartments or tanks and voids and such within the body of the boat or the ship. It would be nice if i could in advance flag the major boundaries (sides of the plating/solid or surface in question) then just create a plate surface at "z" altitude then say "create surface within these boundaries, of given thickness, continuously in contact throughout the edges, upper and lower.
So far as i know, in VC 2D/3D, i have to create a surface bigger than i need. Then I do a surface to surface intersect, then create a thickened solid and do a surface-surface intersect to get the contact surfaces. Then i remove the surfaces extending outside the hull. Sometimes i do it in other orders, but in the end i turn off the layer containing the surface or delete it to keep the model size down. But, the goal is more to get a surface. I realize i can keep the surface and move it around to adjust the surface contact, but i care more about the solid.
Anyway, it IS fun using ViaCAD, and maybe someday I'll get on to Shark LT.