Maybe someone has the same problem and can give me an advice, how to fix it.
When l try “add hole” or “divide” terrain, in panel errors appears “hole operations failed”, “division operations failed”.
I suggest you to check the following checkboxes:
This problem happens when boolean operations are used to model holes, cut & fills and paths. If the boolean operation fails, or if the resulting mesh is bad, then Lands rolls back the operation and shows the problem in the Errors tab.
Unfortunately, boolean operation fails quite often, specially in Rhino 7. And they are more likely to fail if you concatenate several modelling operations. In your example you might had the command line option “Divide=Yes” when you created the hole, so that a division has also been created.
We have this issue in the top of our priorities for version 5.7, we expect to dramatically increase the success ratio of boolean operations. Meanwhile I suggest you to use the gridded surface to model your terrain. Please note that you will have to adjust the cell size to your needs.