Error: Mesh to T-Spline conversion failed

[stefan.elsen]

I converted a mesh I use in 3ds Max to quads so that (in theory) T-Spline conversion should work in Fusion 360. Import works, the geometry displays correctly. Conversion fails, however, with no additional information other than the error message itself.

I attached the obj file. It's a cage and might not even be usable in its current form.

[TrippyLighting · Accepted solution]

When opened in Blender it looked like there were two polygons missing.

I added those and now it converts. 

[stefan.elsen]

Ah. At first that did so not make sense because the mesh does not miss any faces in Fusion, the T-Spline conversion does not warn about anything, and the mesh does not have missing faces when re-importing the obj in 3ds Max.

I don't have Blender installed so I couldn't test that (I kinda hate Blender but can understand if others like it just fine).

So, then I opened the obj in a text editor and spotted the issue: Two 'quads' are actually 5-edged polygons but reference the same vertex twice, making them look like quads. I have zero idea how that could happen, why 3ds Max does not detect/avoid that, or how to get rid of it without being able to see them. But for now I just fixed the obj file and reimport. Sure enough that worked and I could move on.

On a side note, shouldn't the conversion process at least warn that there is a polygon in there?

And fixing that during import should be a no brainer. I mean, it does warn about triangles and normal polygons, doesn't it?

At any rate, you saved my day. Much appreciated!