Re: [fltk.general] filled non-convex polygon disappears when rotated

GitHub FLTK Project   FLTK News RSS Feed  
  FLTK Apps      FLTK Library      Forums      Links     Login 
 All Forums  |  Back to fltk.general  ]
Previous Message ]New Message | Reply ]Next Message ]

Re: filled non-convex polygon disappears when rotated Ian MacArthur 06:04 Oct 25 top right image
On 24 Oct 2020, at 16:29, Paul Hahn wrote:
> Yep, you are right -- the doco mentions fl_begin/end_polygon works for CONVEX polygons, and fl_begin/end_complex_polygon works for CONCAVE polygons (also). I apologize for not paying attention to this initially.

Well, so long as it is working now, that’s all good.

> BTW winding order is addressed in a note for fl_begin/end_complex_polygon, but for fl_begin/end_polygon (convex case), I see no mention of a constraint for CCW vs. CW traversal.

I don’t know the specific implementation in fltk, but for a figure that is “known" to be convex you can reliably infer “inside” and “outside” of the polygon without that, so that may be the way it works. And why you need to use “complex_polygon” for the concave figures, of course.

As to why the “+” polygon works in the orthogonal cases, I imagine that’s just an edge case... probably...!

You received this message because you are subscribed to the Google Groups "fltk.general" group.
To unsubscribe from this group and stop receiving emails from it, send an email to
To view this discussion on the web visit
Direct Link to Message ]
bottom left image   bottom right image
Previous Message ]New Message | Reply ]Next Message ]

Comments are owned by the poster. All other content is copyright 1998-2020 by Bill Spitzak and others. This project is hosted by The FLTK Team. Please report site problems to ''.