I use moi to convert .STPs to .FBX and occasionally run into errors like this on models. Any ideas what causes this? Assuming its from Solidworks or Catia (whatever the engineers are using to make the models) and the .stp export?

well, there are different step-file variations and one should know about the originating cad-system being used, just check:
https://en.wikipedia.org/wiki/ISO_10303-21
https://www.capvidia.com/blog/best-step-file-to-use-ap203-vs-ap214-vs-ap242

best regards

Hi ironsightdesign, usually that's a messed up trim boundary on a closed surface where it was tricky doing the "split at seams" processing.

Different CAD programs can represent trimming boundaries fairly differently and one of the big differences is that some systems allow an edge curve to cross over the "seam edge" of a closed surface. Some systems, like the one that MoI is based on, do not allow an edge to cross a seam and so some edges may need to be cut at the seam crossing location.

This seam-crossing cutting process can sometimes be a tricky operation.

Is it possible for you to e-mail that .stp file at moi@moi3d.com ? It's something that I want to try and improve.

- Michael

Thanks for the explanation, Michael.

Sure, I'll send over that piece.