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11:27
Check out the interactive graph editor that @Kuba wrote for IGraph/M. You can easily install IGraph/M using the instructions here. While this is an early version, we'd be grateful for any feedback on usability.
3
 
3 hours later…
14:08
@shaihorowitz Another way:
starPolygon[r : _Rational | _Integer,
   opts : OptionsPattern[Polygon]] :=
  Polygon[CirclePoints[Numerator[r]][[
     Mod[Denominator[r] Range[Numerator[r]], Numerator[r], 1]
     ]],
   opts
   ];

starPolygon[8/3] // Graphics (* even-odd rule *)
WindingPolygon @@ starPolygon[8/3] // Graphics (* solid *)
WindingPolygon is new in V12 along with other polygon enhancements. OuterPolygon@starPolygon[8/3] // Graphics seems to be messed up, so maybe they're not used a lot.
14:38
I'm wondering if anyone would confirm this bug on another system. (I'm on Mac M1 Max, V13.1):
poly = Polygon[
CirclePoints[8][[
Mod[3 Range[8], 8, 1]
]]
];
Graphics[{OuterPolygon[poly], Red, InnerPolygon[poly]}]
I think: (1) the red should be symmetric, whatever else it should be. So (2) OuterPolygon should have colored the two white triangles black. InnerPolygon should have covered them up with red, and colored a small red triangle to the east of center.
@MichaelE2 I get the same output on Windows 10 with Mathematica 13.1
@gdelfino Thanks for the feedback. I've reported it to WRI.
15:13
@MichaelE2 Thanks this is exactly what i was looking for
@halirutan Thank you as well
 
4 hours later…
18:47
@MichaelE2 I'm utilizing the code you showed me with great success (mostly using the WindingPolygon version) but it is very slow to animate large numbers of them into a single ListAnimate. I think this may be because the interior lines are still being calculated even when I precompute the images. Is there a way to once we have the shape only take the exterior of it?
 
3 hours later…
21:34
@shaihorowitz Theoretically, this should work:
Graphics[{
  EdgeForm[Purple],
  FaceForm[Opacity[0]],
  OuterPolygon@starPolygon[8/3]
  }]
But something is buggy about OuterPolygon, as you can see from running the code or image I posted above.
This works on the {8/3}:
Graphics[{
  EdgeForm[Purple],
  FaceForm[Opacity[0]],
  ReplacePart[OuterPolygon@starPolygon[8/3],
   2 -> {{1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 13, 12, 16, 17, 18, 19}}]
  }]
But you have to inspect the result of OuterPolygon to figure out how fix it. Not really a good solution....
Here's a roundabout way:
Show[BoundaryDiscretizeRegion@DiscretizeRegion[starPolygon[8/3]]] /.
 p_Annotation :> {EdgeForm[Purple],
   FaceForm[Opacity[0]], p}
22:01
posted on July 15, 2022 by Guenther Gsaller

Around the beginning of the first COVID-19-related lockdown in Austria, I was confronted with the problem of keeping my motivation up. From 2012–2016, my main tool for creating several Wolfram Demonstrations in 3D was Mathematica. Now, in addition to the Wolfram Language, Blender offered the possibility for physically based rendering (PBR) and high dynamic range […]


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