Recreating a topo drawing in 3d

I have placed an image of a topographical drawing of an area of a property into my Sketchup Pro model. I’m trying to create a 3d model from this by tracing the elevation lines. I’ve used Sketchup for many years but have never done this. The line segments are not snapping to points on my elevation lines. I want to extrude each 1 ft elevation to create a crude 3d model that I can modify to visualize a flattened area for a house and associated cut and fill above and below site. I am wondering if I can turn off the snap feature or whatever causes the line to snap to a place other than where I’ve tried to place it along the image elevation lines. It just occurred to me that I can place a grid over the image and that will work. Can anyone offer a better method?

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No. Of course they won’t. There are no snappable points in an image.

No. You cannot turn off inferencing in SketchUp.

That would be one way. In what form is the image you are using? It might be that you could use a raster to vector converter to get a suitable vector file to import into SketchUp to use as a reference.

Which version of SketchUp Pro are you using? Your profile indicates you are using SketchUp Make 2017. Please correct that. Still on Windows?

Thank you. I know there are no snappable points on an image. I meant to say the line end points are not landing at the locations where I click the mouse. This happens the same way outside of my image. I’m using Sketchup Pro. I believe it is 2017 Windows version. The image is a JPG. I just realized I could and imported the DWG 3d file into a new model. More complicated but I may be able to use that too.

Please correct your forum profile then.

How is that more complicated than tracing the contours manually? If you have a 3D .dwg file you should simply import it and have the contours in 3D. If you want to create a surface, use the Sandbox tools.

More complicated in that I have to go learn how to do it I guess. I’ve designed and built quite a few things using sketchup over the past 20 years or so, but I’ve only learned what I needed and this I did not.

You’ve basically described what is shown below. Possibly disabling length snapping will help. Otherwise, just draw your line segments along elevation lines, creating faces as you move across the grade.

Lines not shown:

After Push-Pull:

After Sandbox:

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It’s not hard to learn how to create a mesh out of level lines, you can do it with the sandbox tool or with a plugin like toposhaper, the way they work is very similar, just select all the lines and click on the tool, it will generate automatically a mesh with the shape of the terrain, if you have the lines on a same plane, you must select all of them but one, then move the lines 1ft deselect the next and repeat until you have all the lines separated 1ft on the Z axis. It’s not hard at all.

Thank you Dave and Francis. This is certainly better than what I was thinking about doing. I’m going to give it a try.

Seems like a lot of unneeded work to go to all the effort described by @francisquitof when you already have a 3D .dwg file you can import. Sounds like you prefer the work harder not smarter strategy. Your call of course.

No Dave, I like to do things smart. Its just I don’t really follow exactly what either of you are trying to tell me. Thanks for calling me stupid.

Sorry. I wasn’t calling you stupid. You told me you have a 3D .dwg file of the topography. All you have to do is import it into SketchUp and you have your 3D geometry. No screwing around tracing an image or moving edges vertically to make it 3D.

If you share the .dwg file we can help you learn how to do that.

For the third time, also please update your forum profile.

Dave, no offense taken. What I have done so far is import the dwg into a template. This is just a learning exercise at this point. You can see the drawing scale on the pdf image I posted. The paper came in at some distance above zero elevation (possibly a drafting error, or not). The topo came in higher. The north arrow came in at zero. I then measured from a point on the topo lines to the plane of the paper and that measurement is the true elevation of that section of my property if I were to scale it 12:1. I tried to show this on my print screen of the model. I had the surveyor place two benchmarks due east-west. The west benchmark is lower. At this point I plan to place the west benchmark at the origin and then scale the drawing up. Then I will try to learn how to work with the topo lines.

It’s hard to tell from your screen shots and it would be easier to help you if you share the actual .dwg. Basically, though, you appear to have most if not all of the geomtry you need in the .dwg as well as some that isn’t needed. Looks like due to the way the .dwg was created you’ll have to move the topo geometry to suit.

For now I don’t want to share the dwg file. I don’t have AutoCAD so I can’t modify it to remove personal information. I’m not too concerned about that but for now I will share the skp. Because the benchmark point was on paper, it did not wind up at the origin first try. I can fix that. Thank you.
Topo-1.skp (704.2 KB)

So I selected the contours and used Weld Edges to weld them together. Then with the contours selected I used From Contours in the Sandbox Tools to create the terrain surface.

An alternative would be to use TopoShaper, an extension by Fredo6 from Sketchucation. It’ll automatically create a skirt around the terrain.

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Thank you!

Dave, sorry for additional questions but I could not find “From Contours”. My PC is far from ideal for graphics and I’m not sure if the Weld Edges actually worked. It appeared to complete but nothing visually evident. I haven’t looked into the TopoShaper yet but I like the looks of the result.

Look in Draw>Sandbox Tools. Or open the Sandbox Tools toolbar.

Single click on a single contour line. Does the entire thing highlight? If so, the edges are welded.

Before you run From Contours select all of the contours and create a group of just them. Then select that group and run From Contours.

Although it’s not a free extension it has a lot to recommend it.

that worked. Thank you again…

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