Export as OBJ creates distorted geometry

Hi, I was wondering why when exporting this particular model as an obj,
that a non-existing(of original model) protrusion of geometry gets created when
exporting as an OBJ file.

Export as OBJ inquiry.3dm (796.1 KB)

Hello- can you show the mesh settings used to export? So far this looks OK here.
I can see a normals problem there at some mesh settings but not an actual displacement.


Hi, yes here is a screen shot ‘collage’ of all the different dialogues for possible settings when exporting obj.

When doing the process of saving again to screenshot all the output options I had set I thought I would do a preview. In that preview I noticed it’s not really the protrusion of geometry but rather the remainder of the circumference of the geometry at that location was missing the ‘protrusion’. As if the ‘proper’ form the geometry was only happening at that location. The remainder instead just being meshed with a series of single angled planar polygons.

The intention of the obj file is for further work in another software package, but also I wanted to export from Rhino the model as a stl file for 3d printing. When I view that stl file, there is nothing wrong with the file and it is created as desired.

Hello - I see the problem at the settings you show - @wim suggests DivideAlongCreases' > Split at tangents = Yes… that seems to sort it out here.

The issue is that surfaces prefer to be G2, curvature continuous, and while it is allowed, to have parts of a single surface only tangent, some things, like meshing, sometimes, do not work well, so splitting into multiple faces helps. If you must have one surface, set a max Distance edge to surface at say 0.01 or 0.1 and see if that calms that area down.


Thank you Pascal. It seems the best solution is to apply both means you recommended.
My combined screen shots here is for others who may come across the same issue and wonder what type of results different combinations may give.