Rhino mesh export error (WAMIT *.GDF)


After much effort I have created a parametric ship hull form using Rhinoscript. I want to generate a mesh for the hull surface and export it as a *.GDF file.

The surface is generated simply using the -_Loft command. I can create the mesh as well. When I export the mesh, only the mesh at stern of the vessel gets exported. When I try to just export the mesh of the vessel side surface, I get the error message:

WAMIT: No objects to save
Error writing file C:\Data\Test.GDF

I am attaching the hull file. Can someone explain me what I need to do so that I can export the mesh in *.GDF format.


Ship.3dm (140.7 KB)

Seems to work here, if I select one of the side surfaces and export as .gdf, it tells me “Wrote 1 patches.” If I select all 4 surfaces it says “Wrote 4 patches.”

I think you’re getting the error messages trying to export the curves, not the surfaces. Make sure you have the surfaces selected and not the curves before running Export.


I am sorry I did not created the mesh in my previous upload. If you export the surface directly as GDF, you get patches which are used in Higher Order Boundary Element Method. For Linear Boundary Element Method I need to create quadratic panels like the one attached in this post.

If you select the mesh only and try to export, it gives the error I mentioned. However, if you run the command _RebuildMesh and then export the mesh, for some reason it is working. Not sure why? Since I am going to do this task automatically for the parametric hull, I need to make sure the mesh generation works properly every time.

Please have a look and let me know if you find out why this is happening.

Thank you for all your help @Helvetosaur.

Ship.3dm (243.0 KB)

The mesh has a zero-length normal - RebuildMesh cleans that up I imagine. My guess is this normal is at the location near the bow where the U and V directions are parallel.


Thanks @pascal. Is there a way I can determine the existence of zero length normal through the script?