How do I “BooleanDifference” (or any other way) on a non flat surface and create the exact same depth on the entire cut/subtraction?
I projected the flat curves of the river onto a topography, making it following the terrain. I did not move the curves so it still lies and following the terrain perfectly. Then I patched the curves creating surfaces, and then extruded the surfaces with a thickness. I thought by now this would create a object which extruded down into the terrain with the exact same depth throughout the path of the river, so I could just BooleanDifference them and create a river in the terrain which would have the exact same depth following the entire river from beginning to end. But it did not! Somehow when I patched the projected curve, or when I extruded the surfaces Rhino altered the rivers curves vertically.
As you can see on the red markings on the screenshot the river has different depths. I want it to have the exact same depth everywhere on the terrain.
In general the surface Patch creates will not exactly follow the input curves.
An alternative approach:
Extrude the projected curves the desired depth.
Copy the terrain surface at the desired depth below the original.
Trim the original surface and the copied surface with the extrusions - or - Split the original surface and copied surface with the extrusions and then Delete the unwanted parts.
Join
If you need additional assistance upload the original surface and the projected curves.
I have some problems with it. I tried to upload the file but it is slightly bigger than 20 MB so I can´t. I have tried saving with the option small file size. I have also scaled it down to scale 1:10000. Any thing more I can try to make the file size smaller?
Hello- can you post a file with just the curves you’re using? I think what I’d do here is Split the surface with the curves and ExtrudeSrf the split out river bit, then from that. ExtractSrf the top, and Join the rest to the not-river part of the split.
Or Move the split river part down and extrude the edge curves back up and Join.
Yeah, I know. Just thought it might help since the terrain is in scale 1:1 and approx 8000m x 8000m big. It can be a bit heavy for the computer to process. It was a bit easier when it was in smaller scale…
