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In geometry, a polygon with holes is an area-connected planar polygon with one external boundary and one or more interior boundaries (holes). [1] Polygons with holes can be dissected into multiple polygons by adding new edges, so they are not frequently needed. An ordinary polygon can be called simply-connected, while a polygon-with-holes is ...
A polygon with holes is an area-connected or multiply-connected planar polygon with one external boundary and one or more interior boundaries (holes). A complex polygon is a configuration analogous to an ordinary polygon, which exists in the complex plane of two real and two imaginary dimensions.
Referring to the image above, ABCM is an external boundary of a planar region with a hole FGHJ. The cut ED connects the hole with the exterior and is traversed twice in the resulting weakly simple polygonal representation. In an alternative and more general definition of weakly simple polygons, they are the limits of sequences of simple polygons.
A polygon ear. One way to triangulate a simple polygon is based on the two ears theorem, as the fact that any simple polygon with at least 4 vertices without holes has at least two "ears", which are triangles with two sides being the edges of the polygon and the third one completely inside it. [5]
The shrinking process, the straight skeleton (blue) and the roof model. In geometry, a straight skeleton is a method of representing a polygon by a topological skeleton.It is similar in some ways to the medial axis but differs in that the skeleton is composed of straight line segments, while the medial axis of a polygon may involve parabolic curves.
Covering a polygon (which may contain holes) with convex polygons is NP-hard. [15] It has also been shown to be -complete. [16] There is an O(log n) approximation algorithm. [17] Covering a polygon with convex polygons is NP-hard even when the target polygon is hole-free. [4]
The problem may be solved in polynomial time when the area to be guarded is a simple polygon. [1] [2] [3] The problem is NP-hard for polygons with holes, [1] but may be approximated in polynomial time by a solution whose length is within a polylogarithmic factor of optimal. [4]
Star polygon – there are multiple types of stars Pentagram - star polygon with 5 sides; Hexagram – star polygon with 6 sides Star of David (example) Heptagram – star polygon with 7 sides; Octagram – star polygon with 8 sides Star of Lakshmi (example) Enneagram - star polygon with 9 sides; Decagram - star polygon with 10 sides