I need to take these Push-pulled shapes and make a “smooth” mesh, overlaid on top of them in a similar way to how a blanket would be draped over.
Ideally I would like this “blanket” mesh to be the average of all the horizontal faces, rather than just sitting on top of the highest points.
Thanks!
Do you want to retain the zoning boundaries? that would seem complex!
or just average the centrepoint elevation of every horizontal surface ?
It is not clear how big an area you have to do this too but like many things in SU… often it is quicker to just redraw / create than research some tricky dicky method to automate the task in some way!
Personally if the site is not much bigger than you show I would make a copy of the original, flatten it to 2d… to give you a zoning pattern you can drape on a new terrain… then manually place guidepoints at the relevent points on your existing 3d model… group them and covert them from a point cloud to a 3d surface…
PS… that is an unusual (and seemingly inefficient) way to depict a 3d subdivision… was it produced in some other software? Knowing your expertise I am confident you did not create it 
You should look at Valiarchitects 3d road tools if this is a frequent exercise…
just realised it is you Sam posting… hell you know more about this than me
Anyway… I would dedicate a few hours to doing it manually… less strain on the brain !
If you can find a way to select all the vertical edges in your model, you could try adding the surface with the Sandbox from Contours tool
Another option along those lines would be put a centrepoint on each face (Centrepoint all), then with a vertical Edge as a Component place one at each guidepoint, (Guide Tools), then Sandbox to create the terrain over those verticals.
Then hit with SUbD.
hmm, I think there is an extension to do that… but is the relevent elevation an edge or is it in the inferred centre of the prism?
Maybe an extension to define the geometric centre of a prism?.. unfortunately some prisms seem merged… others are not…
It is a really weird way to depict a terrain
Using @Box approach above I think @Fredo6’s TopoShaper can create a smooth interpolated surface between guide points.
Thanks Gary
Some good suggestions and it never hurts to hear what others thing because , even if we think we know something already, a slightly different technique can make all the difference - and can prompt us to think of our own new techniques.
I have Instant Road Nui but it doesnt seem to do verticality very well. Its more about draping than actually setting out a vertical spline for a road to follow. I can get a decent result by creating my own curve then Upright Extruding a road profile along it.
Preparing a 2d site plan (urban blocks and streets) and then push-pulling the blocks up to the desired height is easy and quick (if you know all the technical parameters of slope, orientation, access, retaining walls and batters, drainage and other constraints…so it’s a bit of mental gymnastics!).
This screenshot shows a tiny fraction of the development proposal.
@Box Thanks for the workflow ideas,…this is helpful. I think your Points+SubD method is the closest I can get in a semi automatic function.
I’m going to try overlaying a grid of points and seeing if that gets a better result due to having a finer grain/resolution. I may also try a few tricks like using Copy along Path to create objects (points) in places that I want more detail/edge definition.
Toposhaper looks useful too… Man I am getting a crazy amount of extensions installed…!
At the moment I’m using Surface from Contours combined with some manual flipping and shifting, then Sub D and Smooth.
Building contours on a SubD model sucks…migh have to try Toposhaper for that, too.
