MeshIntersect and split planar surface along (attempted) split Mesh


I am new to Rhino, so apologies if this question has an obvious response. I have a mesh for a body (ship) that I want to create enclosed flat surface within (water surface). I don’t have the hull shape, only the panel model (node coordinates). The method I found for doing this it to create a rectangular surface along the desired plane and use MeshIntersect to generate a curve that I again would use to split the rectangular surface. The resulting interior surface is then to be meshed. When I try this method on one particular mesh, I get an error message that the split cannot be executed because the plane and curve may not intersect. When I study the curve it is closed and ends at the plane edges like it should. however I see that it has some points that are not visible in the mesh (see caption). Also when I export a mesh file (.GDF) and import to another program, I get panels that were not visible in Rhino. It seems the origin of the problem is that I exported the mesh from Blender where I had tried to split the mesh along a plane in order to produce a waterline. I then imported the mesh and used MeshRepair in Rhino. It seems however that the panels I wanted to split in two actually haven’t split (see caption). Also the program that uses the panel model for calculations tells me it does not have a closed waterline, which i suppose is because the panels didn’t split properly. This is the main reason why I have to split the mesh in the first place.

I hope someone here can guide me towards a solution to my problem. If possible I would prefer to use Rhino to split my mesh and not Blender, but I understand this is a weakness in Rhino. The goal of the process is WAMIT (.GDF) mesh files for diffraction analyses.



Hei Helle -
Could you please post the 3dm file? It’s rather hard to tell what’s going on from the description and the pictures.

Unfortunately I can’t due to confidentiality reasons.

Hi -
Perhaps uploading to Rhino - Upload to Support is an alternative? Those files will not be made public. Also, we don’t need the entire file, it sounds like just a NURBS plane at the correct elevation and a curve would be enough to reproduce the issue?

Or am I misreading that?

All meshes are essentially triangles. You can get quads and Ngons but those are just hiding the triangles. Perhaps those extra points are on the edges of hidden triangles?