Triangulate_EC can't get correct result when two polygon has one common node

[GoogleCodeExporter]

Hi Ivan Fratric,

I use Triangulate_EC to triangulate polygons with hole. When the hole and outer 
polygon have common node, the result is wrong. Could you please help me to take 
a look at it?
Thanks,

Tang Laoya

PS:
data example 1:
2
4
1
 -1.191966510797976E-003  0.202231151541577     
  8.150796829630741E-003  0.186049010752862     
  2.980143192424173E-002  0.198549010752862     
  2.045866858381302E-002  0.214731151541577 
8
0      
  3.525591640424161E-002  0.213001949189431     
  4.514750408646251E-002  0.211126769678226     
  4.301140661905761E-002  0.181202914852858     
 -1.683630303167994E-002  0.185475109787668     
 -1.470020556427498E-002  0.215398964613036     
 -4.642556696250064E-003  0.215850079145971     
  1.537278144042436E-002  0.215352008559904     
  2.045866858381302E-002  0.214731151541577     


data example 2:
2
4
1
  2.980143192424157E-002 -0.198549010752862     
  8.150796829630581E-003 -0.186049010752862     
 -1.191966510798143E-003 -0.202231151541577     
  2.045866858381282E-002 -0.204731151461601
8
0       
 -4.642556696250190E-003 -0.215850079145971     
 -1.470020556427507E-002 -0.215398964613036     
 -1.683630303168007E-002 -0.185475109787668     
  4.301140661905749E-002 -0.181202914852858     
  4.514750408646243E-002 -0.211126769678226     
  3.525591640424149E-002 -0.213001949189431     
  2.045866858381282E-002 -0.204731151461601     
  1.537278144042421E-002 -0.215352008559904     

Original issue reported on code.google.com by [email protected] on 10 Nov 2012 at 7:04

[GoogleCodeExporter]

Hi and sorry for the late reply. The library indeed doesn't handle such cases 
as in the context of PolyPartition, a polygon where a hole is touching the 
outer edge is considered self-intersecting. This is something that might be 
improved in the future, however I don't have any specific timeline at the 
moment.

Original comment by [email protected] on 24 Feb 2013 at 4:26

• Added labels: Priority-Low, Type-Enhancement
• Removed labels: Priority-Medium, Type-Defect

[GoogleCodeExporter]

This feature would be very useful to me.  Not sure if this is something that 
you have an idea on how to implement (and I could potentially help with) or if 
this is simply too difficult a problem to solve.

Original comment by [email protected] on 24 Feb 2015 at 2:55

[aaronfranke]

This is still reproducible in the latest master. Here are some updated test cases:

Test case 1: issue-3-ex1.txt, output: issue-3-ex1.zip

Test case 2: issue-3-ex2.txt, output: issue-3-ex2.zip

[ivanfratric]

FWIW I believe that polygons like this could be supported by adding a preprocessing step that would merge two polygons if they have a common node, but I never got around to implement that.