I have a problem with a surface that looks ok from a side angle, but when you pan round you can see through it. Has anyone seen anything like this and/or know how to fix it? My fallback position is to replay the steps I did from the last known good position and check at each stage, but there is a few hours of work in that.
To get to my current point, I started out with a SubD solid, then converted ToNURBS and then did some boolean differences to create cutouts where other objects will fit. At some point along the way, in one of the cutout bits I ended up with a surface that looks like it’s there (because the cross lines on the surface can be seen) but then it’s possible to see through it and inside the shape. See screen shots below.
I’m able to create a curve around the border of this surface and generate a surface from planar curves, but unfortunately Rhino says it can’t do the Edit, Join when I try to join the new surface to the rest of the solid. I also tried to create a solid by extruding this curve a short distance, capping the planar holes and then doing a solid union but that failed too.
Rhino does not think it’s a bad object when I do SelBadObjects.
When I try to convert to mesh something interesting happens that may be a clue as to what is going on. In this bit of the model a partial surface is created that does not extend to cover the entire opening.
If I export to STL I get much the same result and the downstream slicing software can’t process it.
Angled view shows the lines crossing the expected surface
Straight on can see right through the surface
Mesh From NURBS object showing smaller surface in the middle of the opening