Invalid brep when doing a split

I’m building a terrain site with a grasshopper.
But when I split the land with the split command, it creates an invaild brep.
The invaild brep is causing problems with subsequent operations, how can I fix this?

Also, creating lands via split seems to be taxing the computer, is there a more efficient way to do it?
site.3dm (1.6 MB) (33.2 KB)

There are several issues with your model, the most obvious one being the painfully slow response time when opening the file. Projecting curves to a wavy surface (the terrain) and then extruding them can be problematic. Another problem is that you appear to be extruding them in two directions, up and down? But you didn’t graft inputs so one goes down and the rest go up.

I replaced Split Brep Multiple with SrfSplit using the projected curves and made a few other changes. The effort to create a “solid” from the roadways (bottom right) still fails though, due to an invalid brep result from Brep Join. (pink group, disabled) (26.5 KB)

P.S. Maybe I messed up your goals? It’s a little confusing.

It didn’t solve all my problems, but it helped a lot because what I wanted was not an invalid brep on the road part of the vehicle!

I’ll try to find and fix the rest of the issues on my own :slight_smile: