PolyK
"Enhance your polygons."

Documentation

Polygon is an array of X,Y coordinates. E.g. [0,0, 1,0, 1,1, 0,1] is a rectangle.

In coordinate system, where X goes right, Y goes up and edges are arrows going from lower to higher indexed vertex, the inner side of polygon is on the left side of arrow.

PolyK functions

• IsSimple ( p : Array ) : Boolean

  Checks, if polygon is simple. Polygon is simple, when its edges don't cross each other.

• IsConvex ( p : Array ) : Boolean

  Checks, if polygon is convex. Polygon is convex, when each inner angle is <= 180°.

• GetArea ( p : Array ) : Number

  Returns the area of polygon.

• GetAABB ( p : Array ) : Object

  Returns the Axis-aligned Bounding Box of polygon in this format:

  {x:0, y:0, width:0, height:0}

  Where "x" is the smallest X coordinate of all vertices, "y" is the smallest Y coordinate, "width" and "height" are box dimensions.

• Triangulate ( p : Array ) : Array

  Computes the triangulation. Output array is array of triangles (triangle = 3 indices of polygon vertices). E.g.:

  var ids = PolyK.Triangulate([0,0, 1,0, 1,1, 0,1]);
  // ids == [0,1,2, 0,2,3]

  Works with simple polygons only.

• Slice ( p : Array, ax : Number, ay : Number, bx : Number, by : Number ) : Array

  Slices the polygon with line segment A-B, defined by [ax,ay] and [bx,by]. A, B must not lay inside a polygon. Returns an array of polygons.

  Works with simple polygons only.

• ContainsPoint ( p : Array, ax : Number, ay : Number, ) : Boolean

  Checks, if polygon contains [ax,ay].

  Works with simple polygons only.

• Raycast ( p : Array, x : Number, y : Number, dx : Number, dy : Number) : Object

  Finds the closest point of polygon, which lays on ray defined by [x,y] (origin) and [dx,dy] (direction).

  Returns an object in this format:

  {dist:0, edge:0, norm:{x:0, y:0}, refl:{x:0, y:0}}

  "dist" is the distance of the polygon point, "edge" is the number of the edge, on which intersection occurs, "norm" is the normal in that place, "refl" is reflected direction.

  Works with simple polygons only.

• ClosestEdge ( p : Array, x : Number, y : Number) : Object

  Finds the point on polygon edges, which is closest to [x,y]. Returns an object in this format:

  {dist:0, edge:0, point:{x:0, y:0}, norm:{x:0, y:0}}

  "dist" is the distance of the polygon point, "edge" is the number of the closest edge, "point" is the closest point on that edge, "norm" is the normal from "point" to [x,y].