Modelling streets from a toposurface?

Streets from toposurfaces

I would like to ask for suggestions on how to achieve a straightforward method for modelling streets from toposurfaces. Please take a look at the attached file (2 pages of figures with some text) where I explain what I am trying to achieve, and also the questions I am posing.

The purpose of this is not to match the capabilities of tools such as Autodesk Infraworks, but basically to be able to visually express to our clients our ideas for urban design, which will later be transferred to the proper consultants for a more detailed work.



Not sure as to what advantages converting Revit toposurface to a Revit Floor slab presents for street modeling.

Assuming there are advantages in doing so, why don’t you just split the toposurface in Revit (so that the edges of each of the split parts maintain their levels) and then convert one or more to floor slabs using Dynamo

Apologies, if my response completely missed the point of your exercise.

Vikram, no need for apologies when you are always very helpful! The main reason for modifying the slabs rather than the toposurfaces is because toposurfaces have a very limited capability for editing boundaries: you cannot split them by a line or customized geometry that can serve as a reference (at least when the topo is created by points).

The advantages of converting toposurfaces into floor slabs are that I can attach walls to it, I can easily change its base offset (difference in level between the footpath and the street), change materials, etc.

I have also tried before creating an adaptive component with the street profile running on a spline, which would be placed according to lines (centreline of the street) that are projected onto the toposurface. The problem with this is that the adaptive component would flip when I move any of the adaptive points onto the Z axis… there was no way to keep the street horizontal! It worked fine on a flat plane, but its very unlikely that this would ever be a real case scenario for urban design!

Hope this helps!

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Francisco, you can actually quite conveniently split a toposurface in Revit.

Seems to me that it would make sense for you to first split the surface as required and then convert it to a floor slab


Sorry for not explaining it correctly, Vikram. You are right about how easy it is to split a toposurface, but what I was trying to say (very badly redacted), is that if you create the toposurface first, it is much harder to create a floor that matches the footprint of the toposurface, since it is harder to align the boundaries of a floor to a toposurface.

The right way i should have explained is (edited): “The main reason for modifying the slabs rather than the toposurfaces is because Floors (not toposurfaces) have a limited capability for editing its boundaries according to a reference, such as a toposurface.” So, if you have an irregular toposurface, it is difficult to perfectly match a floor to the toposurface boundaries.

Sorry for the confusion, and hope this clarifies my goal…

Alright, here is an alternate approach. With a roof, instead of a floor

This may not actually address your problems, but it’s something you can explore.

dyn File: TopoSurf.dyn

rfa File: topoForm.rfa

The dyn file converts a set of points extracted from a Revit topo surface to a polysurface.

The polysurface is imported into a Conceptual mass family file.

The family is loaded into a project and a Roof by Face is created.


Another method - if you’re working in Civil3D, you can export to 3ds Max Design, and after that to Revit, you’ll get a way better results

Rade, we do not use Civil 3D in the office, but thanks for the suggestion.

Vikram, although it is not exactly what I was looking for, it certainly looks very interesting and a clean solution. I could use that approach for other challenges in the office. Would you share a screen shot of the nodes, so I can re-create it in the earlier versions of Dynamo I am using (0.7.5 or 0.8.2)?


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Dynamo files are backward compatible (haven’t tried in 0.7 though)

In any case below is the code, not nodes, but it should give you a fair idea of which nodes to use (just in case you prefer nodes)



Have you tried the free plugin from Autodesk ‘Site Designer’? I’ve been playing with it and it has pretty interesting functionality.

Admittedly the reviews are pretty mixed.

There are some good You Tube tutorials.



To accomplish what’s in your pdf you can first use subregions or divided surfaces and make separate floors from them, applying an offset parameter for the roads.
Alternatively, you can try the site designer. I like it, but I hear a lot of negative feedback about it.

Hi Viktor,

I have tried the Site Designer before and I never got it to work as expected… Good news you have been successful with it.

Consider DirectShape - - can also use the Category Roads!