Modeling Roads and Topography from Site Plan

I am trying to model a land subdivision with roads and topography imported from a CAD file. (Sketchup Pro 2019)

The image is flat and I have the elevations in a PDF so I just need to raise the lines/faces to the correct elevations. I have watched a few Youtube tutorials on roads but they revolve around existing terrain. I am creating the terrain as I go?

Is there an extension that can do this? Any feedback helps. Thank you

If the CAD file is truly flat, you could use the Move tool to move the contours vertically as appropriate and then use the Sandbox tools to generate the terrain surface from the contours. There’s also TopoShaper from Fredo6 at Sketchucation that has more capabilities but I’d try the Sandbox tools first.

As for the road, if the contours go across it in your CAD file, you probably don’t need to do anything special. There are a couple of tools in the Sandbox tools that can drape or stamp into the terrain surface if appropriate.

If you shared the CAD file or the .skp file with the imported CAD file, it would be easier to give you more precise direction.

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Thank you for the response. Here is the file I am working with. There are some double lines along the road I am currently cleaning up. Should my first order of business to make everything faces before adjusting elevations?

Thanks again

Site Plan Topo Roads Lots from CAD.skp (7.6 MB)

I think the first order of business is to get rid of unneeded edges in the model. Only keep what you really need. setbacks and lines in the parking lot aren’t useful for generating the terrain, for example. It would be easier to start by deleting all of the layers so all geometry has Layer 0 (Untagged in later versions) associated with it. I’d then run Eneroth Auto Weld (Extension Warehouse) to weld all weldable edges. That’ll make handling them easier.

Note, if you still need those lines that you are deleting, make a copy of the imported CAD geometry and group it. Give that group a layer/tag and turn it off so you can bring it back later when you need it.

After that I would work on moving the contours in the Z-direction as appropriate so that you can generate the terrain surface from them. Might still need some refining after that but you should be able to manage it with the tools included in the SandBox tools.

As far as a face in the beginning, you might want to draw a large rectangle and make it a group to place under the drawing. This will help make zooming and orbiting easier.

FWIW I untagged all of the geometry…
Screenshot - 7_22_2022 , 11_17_54 AM
Then I exploded all components, purged unused stuff, and removed the materials. Finally I ran Auto Weld on all of the geometry.
Site Plan Topo Roads Lots from CAD purged and welded.skp (693.4 KB)

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This is great info. Thank you! I am currently cleaning the lines but I will see if I can only the layers I need from the file creator. (I don’t know/have CAD unfortunately)

I am not familiar with Eneroth but will check it out. And the larger rectangle suggestion is something I never considered. Thank you again!

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See the edit to my previous post. If you can get just the contours and road outlines that will help but you’ll still want to do some cleanup. Notice in the attached file if you select a contour you get long runs of edges instead f just little short edge segments.


So something I just discovered -the CAD file do come in as layers so I was able to turn off a lot of layers instead of manually doing it.(This is my first CAD import so I am at the bottom of the learning curve).
Question. The topo layer comes in as with elevations, but I need to flatten to align with the road profile. I used FredoScale → Box Scaling to flatten it to zero but it makes it nearly impossible to ungroup.

Is there a better way to do flatten it?

The prooblem with the geometry and layers is that the layers don’t prevent some geometry from merging with other geometry. Turning off the visibility for some layers will hide the geometry but the rest of the model can still be affected by it. In SketchUp all edges and faces should have Layer 0 assigned them. Only components and groups should get layer assignments.

If you have to flatten all the contours, Box Scaling works as do some other flattening extensions. Not sure why you have to flatten them, though. Seems to me you should be able to do what you need without that.

My idea is to flatten the topo lines and overlay onto the road profile. This way I know the exact point to raise my road elevation to. (The topo grouping is in the file I originally attached).
Am I approaching this from the wrong angle?

Seems like more work than you should really need to do. Another option might be this.

Here I’ve used Sandbox Tools>From Contours to create the terrain surface. I copied some of the road geometry up above the terrain.

Then I used SandBox Tools>Drape to drape those edges into the terrain surface group.

I didn’t edit the terrain surface at all and there seem to be some missing contours so the surface probably isn’t exactly right.

You are correct, the topo is missing some contours so it seems hard to use it as a starting point, even though they are correct. My first attempt (before I got the CAD file) was to trace all the lines from an image and adjust manually. The photo below is how far I got before I had to reevaluate my approach. I was using Toposhaper but it wasn’t providing what I needed.

I have been working through the CAD file and got cleaned with faces but running into the same problem. Maybe if I focus on one aspect, the others can fall into place. See attached.

I isolated the road. (in blue) The numbers represent the elevation I am trying to achieve. (at least incrementally increasing at the 2 foot intervals)
How would one go about modeling the road to the right elevations?

Site Plan Road Topo.skp (8.2 MB)

Not sure what you’re up to but you could do 2’ Push-Pulls (including ‘curbs’ - not shown):

Then erase (a lot) of extra geometry and do Sandbox-> Create Terrain from a set of edges, using elevation lines.

Or, weld the cross-lines, use crtl+move to copy downward 2’ per elevation line to get something like this:

In either case the idea is to get the elevation lines set for Sandbox-> Create Terrain from a set of edges.

Here’s what part of it would look like after using Sandbox Tools (The first two ‘flat’ segments are deleted):

You can see that I used a ‘straight’ line that Sandbox Tools created vs. the ‘V’ shape on the original. That leads to another point: you might be better off to draw new lines across the road, drop those to the elevations, then use Sandbox Tools to connect the segments because your lines are all broken up.

You could then use the drop tool (as DaveR mentioned), to drop your curbs back onto the road.

Have a look at Vali Architects extension “Instant Roads” if you have a lot of roadwork to do, well worth it