Trick to trim a surface with a mesh?

I am importing scanned meshes of boat hulls from a 3D scan and trying to work on a way to find the centerline. After doing _Orient3pt I am using a thin cylinder that intersects with the port and starboard hull, and I then use the hull to trim the cylinder, and then I can click on the midway point of the result.

I can’t get the mesh or the quadremesh to trim these objects even though (especially in quadremeshed version) it shades like a surface. There must be a trick I am missing.

My workaround is to build a 3pt survace ontop of the mesh using the vertices… it works and is reasonably accurate, but I don’t like the extra steps.

Any hot tips on how to either trim/split or assist in finding the middle point another way?


Hi Chris -

You could select both the mesh and the cylinder and run MeshIntersect.

The middle point of a cylinder that is cut with non-parallel ends is somewhat undefined. I take it that the better way would be to create a curve (the centerline of the cylinder) and intersect that with the mesh. That is currently not possible in Rhino (on the wishlist as RH-4221) but you can create a simple Grasshopper graph that does that. With GrasshopperPlayer, you can create a command that you can run in Rhino without having to deal with the Grasshopper interface once you have created the graph.

You could automate it more by also internalizing the hull mesh into that Grasshopper graph and getting Grasshopper to create the line from a single input point.