Editing Polygon (section)

==Computer graphics==
{{Main|Polygon (computer graphics)}}
{{more citations needed section|date=October 2018}}
In [[computer graphics]], a polygon is a [[geometric primitive|primitive]] used in modelling and rendering. They are defined in a database, containing arrays of [[vertex (computer graphics)|vertices]] (the coordinates of the [[vertex (geometry)|geometrical vertices]], as well as other attributes of the polygon, such as color, shading and texture), connectivity information, and [[material (computer graphics)|materials]].<ref>{{cite web|url=https://www.khronos.org/opengl/wiki/Vertex_Specification#Primitives|title=opengl vertex specification}}</ref><ref>{{cite web|url=https://msdn.microsoft.com/en-us/library/windows/desktop/bb147325(v=vs.85).aspx|title=direct3d rendering, based on vertices & triangles|date=6 January 2021 }}</ref>

Any surface is modelled as a tessellation called [[polygon mesh]]. If a square mesh has {{nowrap|''n'' + 1}} points (vertices) per side, there are ''n'' squared squares in the mesh, or 2''n'' squared triangles since there are two triangles in a square. There are {{nowrap|(''n'' + 1)<sup>2</sup> / 2(''n''<sup>2</sup>)}} vertices per triangle. Where ''n'' is large, this approaches one half. Or, each vertex inside the square mesh connects four edges (lines).

The imaging system calls up the structure of polygons needed for the scene to be created from the database. This is transferred to active memory and finally, to the display system (screen, TV monitors etc.) so that the scene can be viewed. During this process, the imaging system renders polygons in correct perspective ready for transmission of the processed data to the display system. Although polygons are two-dimensional, through the system computer they are placed in a visual scene in the correct three-dimensional orientation.

In computer graphics and [[computational geometry]], it is often necessary to determine whether a given point <math>P=(x_0,y_0)</math> lies inside a simple polygon given by a sequence of line segments. This is called the [[point in polygon]] test.<ref>{{cite conference|last=Schirra|first=Stefan|editor1-last=Halperin|editor1-first=Dan|editor2-last=Mehlhorn|editor2-first=Kurt|contribution=How Reliable Are Practical Point-in-Polygon Strategies?|doi=10.1007/978-3-540-87744-8_62|pages=744–755|publisher=Springer|series=Lecture Notes in Computer Science|title=Algorithms - ESA 2008: 16th Annual European Symposium, Karlsruhe, Germany, September 15-17, 2008, Proceedings|volume=5193|year=2008|isbn=978-3-540-87743-1 }}</ref>