Very strange and unusable mesh from simple surface

Rhino Rhino for Windows
1

Cone Meshing Problem.3dm (3.0 MB)

I have spent a few hours trying to convince Rhino to mesh a simple surface. The surface is part of a cone - basically 90 degrees of a truncated cone. It failed with the original surface from another CAD program, then I tried to build it in Rhino by revolving a line, then I tried making a truncated cone solid and splitting it. In all cases, the mesh has “seams” that the downstream software has errors with. The mesh structure is really out there.

Here is the crazy mesh structure:

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image1514×490 66.4 KB

This was made using these settings:

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image529×649 16 KB

When I triangulate the mesh it does not get any better (as expected):

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image1668×526 112 KB

Zooming in a LOT you can see how the triangle edges are not coincident. This makes the next step in the process blow up.

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image921×617 3.94 KB

Can anyone offset some suggestions for getting a proper mesh? Eventually, I will script the solution but right now I have no solution.
Thanks for your help.

2

I get this with these values. When pushed I stay away from density:

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image1804×1081 401 KB

3

Thank you for the quick reply, Scott. Unfortunately, when I reduce the maximum edge length the problem comes back. The overall process requires 0.1” maximum edge length. When I reduce the edge length to 0.25” the mesh structure already looks strange:

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image1750×691 141 KB

When I reduce it to 0.15” the mesh is already “torn” and the saved OBJ file has errors.

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image1661×688 92.4 KB

I guessed that a larger number for the initial quads would help, and it does help the overall structure. However, it still creates some sort of edge in the mesh.

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image1681×701 71.7 KB

Any other suggestions?

4

Hi Henry,

Turning off “Refine Mesh” will stop it from trying to subdivide quads. Then your edge resolution is purely set by the values you enter.

Hope that helps, Steve

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image1445×928 162 KB

5

Thank you for taking the time to reply Steve. I appreciate it.

I was never able to get reasonable results, so we changed the process to mesh the surfaces in another program. That generated a few extra files to control, but the process works fine and the Python scripting in Rhino holds everything together. We seem to use Rhino as a “geometry API” that just so happens to have a GUI. Probably not what the developers intended :slight_smile: