Is it possible to draw a hollow circle using polygon?
Is it possible to draw a hollow circle using polygon?
The question is simple. I have the following commands
r = 0.24;
R = 0.25;
unitcircle =
Table[Sin[[Theta]], Cos[[Theta]], [Theta], 2 [Pi], 0, -[Pi]/
40] // N;
incircle = r*unitcircle;
outcircle = R*unitcircle;
which define the outer points and inner points of a hollow circle. Is it possible to draw such a hollow circle using the polygon command?
Annulus
FilledCurve
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But, with the command polygon no. right? something like playing with the points that you input to Polygon?
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– Msen Rezaee
Sep 18 '18 at 13:06
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If you want to have a differing
FaceForm and EdgeForm and no defects, and also everything on the background to appear in an honest fashion, plain Polygon is not enough. FilledCurve is the way to go.$endgroup$
– kirma
Sep 18 '18 at 19:02
FaceForm
EdgeForm
Polygon
FilledCurve
3 Answers
3
Polygon is always filled (it can be filled with white). Use Circle for a "hollow" circle.
Polygon
Circle
r = 0.24; R = 0.25;
Graphics[Circle[0, 0, #] & /@ r, R]
Graphics[EdgeForm[Black], White, Polygon[CirclePoints[#, 50]] & /@ R, r]
Note that since the polygons are filled, the smaller circle must be drawn on top (last) to be seen.
EDIT: For a red background, either
Graphics[White, Annulus[0, 0, r, R], Background -> Red]
Or,
Graphics[White, Polygon[CirclePoints[R, 50]], Red,
Polygon[CirclePoints[r, 50]], Background -> Red]
You could also use EdgeForm to make the borders more distinct.
EdgeForm
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thanks a lot for the answer
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– Msen Rezaee
Sep 18 '18 at 13:16
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@MsenRezaee the question is, what do you expect to see if there is e.g. a red background.
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– Kuba♦
Sep 18 '18 at 14:03
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@Kuba I expect to see red everywhere except on the thin surface of my circle
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– Msen Rezaee
Sep 18 '18 at 14:07
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@MsenRezaee that is unclear for me. What should be between those black edges, and what should be inside the inner edge.
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– Kuba♦
Sep 18 '18 at 14:15
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@Kuba in the case of a red background, I expect to see red outside the outer edge and inside the inner edge. But not on the thin surface of the circle.
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– Msen Rezaee
Sep 18 '18 at 14:18
Here's one way:
outer = CirclePoints[2, 100];
AppendTo[outer, First[outer]];
inner = CirclePoints[1, 100];
AppendTo[inner, First[inner]];
Graphics@Polygon[Join[inner, Reverse[outer]]]
A hollow annulus is trickier:
Graphics[
FaceForm,
EdgeForm[Black],
Polygon[Join[inner, Reverse[outer]]],
White, Thickness[0.01],
Line[1.03 First[inner], 0.985 First[outer]]
]
I couldn't get away with just a polygon for this one, I had to cover up the line from where the inner circle connects to the outer. Had I done this with a polygon it would still be two polygons and not one. We can also draw another polygon like the first one here above in white to make the first one appear hollow.
As an aside, I see that Annulus has been mentioned but no one has shown how to make it hollow as far as I can tell:
Annulus
Graphics[
FaceForm,
EdgeForm[Black],
Annulus
]
FilledCurve can be used to achieve polygons with holes defined using lines (but also filled Bezier curves and B-splines can be used). Here one is formed by two very circle-like polygons). Red line on background for illustrative purposes:
FilledCurve
Graphics[
Thick, Red, Line[.25 -1, -1, 1, 1], FaceForm@White, EdgeForm@Black,
FilledCurve[Line@CirclePoints[#, 100] & /@ .24, .25]]
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Kind of yes, but should you? No. See
Annulusand if it should be a polygon take a look atFilledCurve.$endgroup$
– Kuba♦
Sep 18 '18 at 13:04