DXF: Polyface meshes with invisible edges return bad geometries

[Alan Thomas]

(I'm filing this as a reminder to myself to deal with this bug in the near future. If this ticket is still open after a few months, you can assume I won't be working on it.)

An edge of a polyface mesh that is marked invisible will not be output as part of the geometry of the mesh. This is likely to render the resulting polyhedral surface geometry invalid. Ideally we would hide only those edges that are not to be shown, but that is not possible with the current infrastructure.

I think when it comes to polyface meshes there is a tension between displaying them as the user wants and rendering them properly for use in 3D modelling scenarios. I'm not sure how to resolve it, but for now let's bin the logic that creates invalid geometry.

[Alan Thomas]

In 41441:

DXF: Always output all edges in polyface mesh, and add styling (fixes #7219)