Hi Helal , This was not a known problem, I will investigate this, and answer you tomorrow or Friday (I cannot start immediately...).
The Union of a rectangle with a hexagonal hole and a triangle intersecting the first polygon
***************************** ***************************** ***************************** ******** ********* ******* **X***** ****** XXX***** ***** XXX****** **** XX ***** ***** ****** ****** ******* ******* ******** ******** ********* ***************************** ***************************** *****************************
returns this polygon, instead of the correct result.
++++++++++++ ++++++++++++++ +++++++++++++++ +++++++++++++++ +++++++++++++++ +++ ++++++++++++++++++ ++++++++++++++++ ++++++++++++++ ++++++++++++
You can use the code bellow to generate the case and some PPM images. You may use a WSQ Viewer to see the polygons.
Please let me know any workaround or anything thats I am missing.
The problem is completely clear, thanks for the useful pictures and source code. Regards, Barend