Hi there,
I’m working on a landscape 3d model and I need to extract a mesh in a specific shape, from a bigger mesh. Can somebody help me? How can I do that?
The final aim is to replace a piece of mesh in the “bigger” model, through a new modeled detail.
Thank you very much!
Hi - you could use the ExtractMeshFaces command for this.
-wim
Thank you for your answer Wim! I tried that, but I never manage to set the shape I want to extract. The model I’m working on has about 1 million faces, so I would like to set a border within which all faces should be extract. Do you have tips for that? I’m a very beginner with rhino, so anything is appreciated 
-serena
Hi,
Rhino is notoriously bad at cutting meshes that has normal faults like naked edges, overlapping faces etc.
Can you share your file so we can see what your problems might be caused by?
Hi Serena - if you use the SelectionFilter panel, you can activate Sub-objects and then deactivate Points/Vertices and Curves/Edges.
Then draw a curve that will act as your selection border and use the SelBorder command.
That should give you what you want.
But, as Jørgen says, Rhino deals badly with bad meshes so if you run into problems with this, please post the file.
-wim