Viewport appearance is acting strange -polysurface faces are missing


After 4 years of rhino use, I am encountering a new problem I cannot find an solution for: some faces are missing in my viewports. The missing faces seem to be based on my point of view (it is always the forward facing faces that are missing.

This problem seems to affect some objects and not others.

Any advice?

Can you post part of the file that shows this?

TEST.3dm (2.5 MB)

Here it is…

Explode the wrongly shaded objects and then immediately Join them back into closed solids to fix the issue. I’m interested in how this could have occurred so we could potentially avoid it from happening at all. Can you tell me anything about where the objects were created and when the issue arose? My hunch was that this was another render mesh issue when objects are far from origin but it may be something else entirely. The model also is in MM and the unit tolerance is set to a non default .01… maybe the model was made elsewhere at a different tolerance and unit?

Also, all of the objects are inside-out. If you call Dir, you can see the normals pointing inward. This shouldn’t happen with objects built in Rhino. It sometimes does with extremely complicated objects, but not these. Notice that when you explode and rejoin, the normals are now pointing out. This makes we wonder if they were made by hand using the sdk. Or, as Brian suggested, if they were originally made far from the origin, numerical problems could occur causing the inside-out detector to fail.

Hmmm… All of the objects were made in rhino by tracing building footprints on the map, extruding, and capping. I did however import some mapping data from Archicad, so perhaps that was the source of the error. As for the tolerances, I selected MM large objects as my starting template…


I can’t reproduce the inside-out solids by extruding the curves. Can you? If you can repeat the problem, please undo back to the curves, save, reopen, and try again. If there is still a problem, please attach the file with just the curves. If not, then we’ll try something else.


TEST 2.3dm (195.3 KB)

Here is the file, with two curves that I successfully reproduced the problem with.


Strange, I can’t reproduce this with your file. I used ExtrudeCrv with the solid option and also used the Gumball to extrude as an alternate approach. Are you using SR 10?

Ok, well the exploding solved it, so if it happens again, at least there is an easy solution.