[OpenSCAD] Getting more information

adrianv avm4 at cornell.edu
Thu Jul 4 11:50:20 EDT 2019


The typical behavior when a polyhedron is invalid is that it works in preview
but fails in render.  Use the "thrown together" option with preview, not
render.  Faces that are incorrectly oriented will appear in purple.  

There's an example here, along with other advice on debugging polyhedra:

https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/The_OpenSCAD_Language#Debugging_polyhedra


DanS wrote
> I'm not sure how to use View->Thrown Together properly
> 
> If I do render.  I see this:
> 
> [image: image.png]
> 
> If right after that I go into View and select Thrown Together  I don't see
> anything in the console that indicates work is being done, my object
> entirely disappears.  I was expecting that if it will take some time it
> might indicate it is calculating.  Likewise, I thought the end result
> would
> be the same drawing but with some facets in a different color (indicating
> maybe missing / degenerate vertices caused things to be inside out).  What
> is the proper way to use View -> Throw Together
> 
> On Thu, Jul 4, 2019 at 11:03 AM adrianv <

> avm4@

> > wrote:
> 
>> DanS wrote
>> > I'm still trying to debug my own code but am frustrated in that I can't
>> > see
>> > where the problem exists.  I get some errors and other messages from
>> > OpenScad but unfortunately they don't point to what it was in my code
>> that
>> > triggered it:
>> >
>> > ERROR: CGAL error in CGAL_Nef_polyhedron3(): CGAL ERROR: assertion
>> > violation! Expr: e_below != SHalfedge_handle() File:
>> >
>> /opt/mxe/usr/x86_64-w64-mingw32.static.posix/include/CGAL/Nef_3/SNC_FM_decorator.h
>> > Line: 426
>>
>> I don't recognize this error specifically, but typically if you get
>> errors
>> relating to polyhedra it means you have constructed an invalid polyhedron
>> with the polyhedron module.  You can select View->Thrown Together in
>> preview
>> which will show reversed faces.  But otherwise you just have to work
>> through
>> your construction.
>>
>>
>> > Likewise, I sometimes get this warning:
>> >
>> >
>> > DEPRECATED: Using ranges of the form [begin:end] with begin value
>> greater
>> > than the end value is deprecated.
>>
>> Yeah, this one is extremely annoying.  There appears to be no way to get
>> OpenSCAD to give you more information about this.  It can be anywhere in
>> your code, or anything that you include.  It could be a degenerate case,
>> in
>> which case you can solve the problem by replacing every occurrence of
>> [a:b]
>> in your code with [a:1:b].  But if it's a mistake in your code, that will
>> just cause the loop to not run---it won't tell you where the problem is.
>>
>>
>>
>>
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>>
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> 
> image.png (27K)
> <http://forum.openscad.org/attachment/26707/0/image.png>





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