Any luck dealing with the "winding order" bug in OpenSCAD?

[Gian Pablo]

When attempting to import some STL files in OpenSCAD, I get this message:

ERROR: Illegal polygonal object - make sure all polygons are defined with the same winding order. Skipping affected object.

The object I am importing is an extruded letter made in Google SketchUp. Another letter in the same font, same size, imports OK.

Can this be fixed in SketchUp? Alternatively, can it be fixed using Meshlab or Netfabb or anything like that?

I have found messages online discussing a "winding order" bug in OpenSCAD, but they were mostly from a 2 or 3 years ago.

[miloh]

On Thu, Jun 30, 2011 at 5:18 PM, Gian Pablo <gian....@gmail.com> wrote:

When attempting to import some STL files in OpenSCAD, I get this message:

ERROR: Illegal polygonal object - make sure all polygons are defined with the same winding order. Skipping affected object.

The object I am importing is an extruded letter made in Google SketchUp. Another letter in the same font, same size, imports OK.

Can this be fixed in SketchUp? Alternatively, can it be fixed using Meshlab or Netfabb or anything like that?

My gut feeling is that this has to be fixed up in sketchup, and that it's not a winding error but a open mesh (whatever the right terminology is for watertight mesh errors) error that results in winding error being reported.   

What do you think, is it possible the model has a little opening at a joint (compared to the working export) that results in this error?

-rma

[Brent Crosby]

Properly, this question should be posted here:
http://rocklinux.net/mailman/listinfo/openscad

I tried breaking a complex OpenSCAD object up into sections, exporting
each section as an STL, then bringing those STL back into OpenSCAD
(like a forced, immutable render() ). It looked good with an F4, but
trying to export the STL gave the winding error.

This is with an STL created by OpenSCAD brought back into OpenSCAD, so
I think there is some underlying sensitivity to winding order that
needs to be addressed.

I am not going to complain though, I think OpenSCAD is awesome for my
purposes.