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graphics - Find all intersection points of complete graph


I want to create a picture like this:


enter image description here


This picture was found in Regular Polygon Divisionby Diagonals.


But these codes are too old to run.


I think I can use Graphics`Mesh`FindIntersections to find all the intersection points.


lines=Line/@Tuples[CirclePoints[7],2];
pts=Graphics`Mesh`FindIntersections[lines]
Graphics[{{Thickness[0.005],lines},{Directive[Red,PointSize[0.02]],Point[pts]}}]


enter image description here


Looks it meets a bug. I need another way or try to fix it.



Answer



This is a brute-force solution that works in version 11.1, but not in the latest version:


lines = Line /@ Subsets[CirclePoints[7], {2}];
pts = DeleteCases[RegionIntersection @@@ Subsets[lines, {2}], _EmptyRegion];

Graphics[{lines, Directive[Red, PointSize[Large]], pts}]


intersection points on the complete graph


In 11.2, the corner points are missed:


missing points


because RegionIntersection[] apparently lost the ability to find intersections of two line segments sharing an endpoint in 11.2:


RegionIntersection[Line[{{0, 0}, {1, 0}}], Line[{{0, 0}, {0, 1}}]]
   EmptyRegion[2]

where 11.1 would give the result Point[{{0, 0}}].


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