baozdemir / polyk

A JavaScript tool for working with polygons.

PolyK

This library was written by Ivan Kuckir.

What is PolyK?

PolyK is JavaScript tool for working with polygons. It uses several basic principles to be super simple and super universal:

• No classes. PolyK does not have any classes or special data structures. PolyK consists of static functions only.
• What is polygon? For PolyK, polygon is an array of numbers. Each two of them are X and Y coordinate of polygon vertex.
• Simplicity and speed. Since PolyK does not make you use any special data structures, it is very easy to implement into your project. Since all JS engines are optimised for work with arrays, PolyK runs very fast.

PolyK was used in the game Tiny Monsters. Do you like the project? Make a donation!

Install

npm

$ npm install --save polyk

bower

$ bower install polyk

web browser ES5

<script src="https://unpkg.com/polyk/dist/polyk.min.js"></script>

Resources

• Homepage
• Demos
  • Point Intersection
  • Triangulation
  • Slicing
  • Ray Casting
  • Closest Edge
• Documentation
• Discussion

API

IsSimple

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

Parameters

• polygon Array<number> [x1, y1, x2, y2...]

Returns boolean true if Polygon is simple

IsConvex

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

Parameters

• polygon Array<number> [x1, y1, x2, y2...]

Returns boolean

GetArea

Returns the area of polygon.

Parameters

• polygon Array<number> [x1, y1, x2, y2...]

Returns number

GetAABB

Returns the Axis-aligned Bounding Box of polygon

Parameters

• polygon Array<number> [x1, y1, x2, y2...]

Examples

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

Returns AABB

Triangulate

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

Works with simple polygons only.

Parameters

• polygon Array<number> [x1, y1, x2, y2...]

Examples

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

Returns Array<number> array of triangles (triangle = 3 indices of polygon vertices)

Slice

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.

Parameters

• polygon Array<number> [x1, y1, x2, y2...]
• startX number Start Coordinate [x]
• startY number Start Coordinate [y]
• endX number End Coordinate [x]
• endY number End Coordinate [y]

ContainsPoint

Checks, if polygon contains [x, y].

Works with simple polygons only.

Parameters

• polygon Array<number> [x1, y1, x2, y2...]
• pointX number Coordinate [x]
• pointY number Coordinate [y]

Returns boolean depth

Raycast

Finds the closest point of polygon, which lays on ray defined by x,y and dx,dy.

"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.

Parameters

• polygon Array<number> [x1, y1, x2, y2...]
• originX number Origin [x]
• originY number Origin [y]
• directionX number Direction [x]
• directionY number Direction [y]
• isc

Examples

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

Returns Raycast

ClosestEdge

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

"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].

Parameters

• polygon Array<number> [x1, y1, x2, y2...]
• x number Coordinate [x]
• y number Coordinate [y]
• isc

Examples

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

Returns ClosestEdge

Reverse

Reverse

Parameters

• polygon Array<number> [x1, y1, x2, y2...]