Swift implementation of Fortunes Algorithm

by iOS Example

VoronoiLibSwift

Swift implementation of Fortunes Algorithm.

This is a port of Zalgo2462/VoronoiLib from C# to Swift. In addition to the original C# library, this Swift library optionally generates polygons for the sites.

Xcode projects

  • VoronoiLibSwift.xcodeproj builds an iOS framework to be used as a library.
  • VoronoiLibSwiftExample.xcodeproj includes the VoronoiLibSwift framework and contains an example iOS App which renders a voronoi graph.

Usage

Generating Voronoi site edges

Make an array of SitePoint<UserData>. The generic parameter UserData can be Void if you only need the edges.
Specify a location for each site point by passing a SIMD2<Double> x,y coordinates value.
Make a ClipRect which will define the borders of the voronoi graph.
Call Voronoi.runFortunesAlgorithm and pass the site points and the clipRect as arguments (and an empty Option set for the options parameter).

let sitePoints: [SitePoint<Void>] = [
  SitePoint(point: SIMD2<Double>(x: 20, y: 30)),
  //other site points...
]

let clipRect = ClipRect.minMaxXY(minX: 0, minY: 0, maxX: 50, maxY: 50)

let result = Voronoi.runFortunesAlgorithm(sitePoints: sitePoints, clipRect: clipRect, options: [])

The result will be a tuple, containing the edges and sites for the Voronoi graph:

(edges: [Edge<Void>], sites: [Site<Void>])

The edges can be rendered like this:

Generating Voronoi site polygons

When you need the exact shape of the sites, for example to paint each site with different colors, you can enable the generation of polygon vertices for each site.

For example, specify UIColor for the UserData generic parameter of SitePoint.
Give each SitePoint a value for the userData parameter (for example UIColor.blue).
Pass a set containing Voronoi.Option.makeSitePolygonVertices into the options parameter of Voronoi.runFortunesAlgorithm.

let sitePoints: [SitePoint<UIColor>] = [
  SitePoint(point: SIMD2<Double>(x: 20, y: 30), userData: .blue)
  //other site points...
]

let clipRect = ClipRect.minMaxXY(minX: 0, minY: 0, maxX: 50, maxY: 50)

let result = Voronoi.runFortunesAlgorithm(sitePoints: sitePoints, clipRect: clipRect, options: [.makeSitePolygonVertices])

The result will be a tuple, containing the edges and the sites for the Voronoi graph.

(edges: [Edge<UIColor>], sites: [Site<UIColor>])

For each site, the polygon vertices are accessable with the property polygonVertices. The vertices are ordered properly and ready to be rendered as polygons.

Use the userData property to get extra infos for the sites like the color to fill the polygons.

Computing the polygons takes more time than just the edes.

The option Voronoi.Option.makeEdgesOnClipRectBorders will also generate edges on the border of the graph (the clipRect border):

GitHub