Can't seem to make a surface out of cad road file

hi everyone, im triyng to make a mountain road from a .cad file.
i would like to have it in 3D but i cant close the lines of the road therefore i cant pull to make it 3d.
It’s my first post here, I hope im following the guidelines.
Can i share the file somewhere?

Check the resources at

This would perhaps be a job for the Sandbox from Contours tool.

ok, thanks!

fixing underlay geometry to close up is a typical challenge. There are extensions out there that will try to clean up things. Typically there is a small gap, or some lines that looks like they are closed but are actually overlapped.

I dont do it often enough to invest in learning the plugins, so I just close it manually, this way: draw some extra line to divide your surface. see if that closes off parts of it. If you can triple click the line and get everything selected then you know there is not more than one gap… Keep going until you have narrowed down the area where the gap is.
It could also be that the linework is not perfectly flat. You will find the problem by closing up part by part.

You can drag the.skp file in the response window if it is not bigger than 15 MB. If it is you can upload it to Dropbox or similar and publice the link here. Make sure the file is open to the public…

I tried using “edge tools” and it seemed to fix it.
The only problem now is i cant make it into a surface, even with the lines closed.

unfortunately the file is bigger i’ll try with wetransfer?
can someone check it out?
thanks btw!

still, even if it is closed, if it is a complex shape, it might need some help in making the surface. divide it, see if both sided closes. then delete the divide lines afterwards. I doubt the geometry, in a separate file, will be 15mb.

you mean something like this?

I typically go between end points. portions of it should close. something more serious seems to be going on if nothing really closes. Is it flat? Post the road in a separate file.

should work, sorry the file is in italian. “strade” is “road”

there can be no surface unless the geometri is flat. I flattened it with “eneroth flatten”, and closed it part by part.

the road itself is 150mb …you should have a strategy on making smaller models.

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thanks a lot!
i would like to have it folliwing a mountain side, that’s why the geometry wasn’t flat.
can i still use the flatten road and follow the old one with geometry?

if you have a terrain model with surfaces, extrude the road above the heights in the model, make it a group, and use “intersect with model” inside the group. that will split the extruded road along the terrain.

With Fredo Curviloft


actually the road is just 40 kb.

there must have been lots of components in the original file.

road clean.skp (42.3 KB)

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thats a nice way to close complex geometry. you might end up with the road being under the terrain. You could just lift it above by half a meter…

If you need the geometry to be editable, where you want to add roads, alter the geometry, you might still want to intersect it with the terrain model.

so, i tried cutting the road with the mountain surface, the only problem is that it’s not “closed” on top and i only have the sides

where can this tool?
is it an extension?

If you now copy this geometry into your terrain model, it will divide up those surfaces of the terrain model, and you then have lots of closed surfaces, mostly triangles, inside you road. You can then select those, and paint them a color.