Update: I used the stamp tool to create a new surface for the road instead. Then I used the drape tool again for the inner lines of the road, and not even those create a new surface even though the terrain from the stamptool is completly flat.
I’m draping lines but as you can see the road is not its own surface (as it was before draping it on to the terrain). Any suggestions what the problem might be? I’ve tried correcting some of the surfaces by adding lines but it only works on occasion (because of the terrain I suppose)
The model is about 50000mm x 50000 in size.