simplify-planar-graph

Simplifies a planar graph by removing small or nearly flat corners.

Example

var simplify = require("simplify-planar-graph")
 
//Create a circle
var positions = []
var edges = []
for(var i=0; i<100; ++i) {
  var theta = i / 100 * Math.PI * 2.0
  positions.push([Math.cos(theta), Math.sin(theta)])
  edges.push([i, (i+1)%100])
}
 
//Simplify it
console.log(simplify(edges, positions, 0.1))

Output:

{ positions:
   [ [ 0.9921147013144779, 0.12533323356430426 ],
     [ 0.8090169943749475, 0.5877852522924731 ],
     [ 0.48175367410171516, 0.8763066800438637 ],
     [ -0.30901699437494734, 0.9510565162951536 ],
     [ -0.7705132427757891, 0.6374239897486899 ],
     [ -0.9980267284282716, 0.06279051952931358 ],
     [ -0.9510565162951535, -0.30901699437494773 ],
     [ -0.5877852522924732, -0.8090169943749473 ],
     [ -0.18738131458572463, -0.9822872507286887 ],
     [ 0.535826794978996, -0.8443279255020155 ],
     [ 0.7705132427757894, -0.6374239897486896 ] ],
  edges:
   [ [ 0, 1 ],
     [ 1, 2 ],
     [ 2, 3 ],
     [ 3, 4 ],
     [ 4, 5 ],
     [ 10, 0 ],
     [ 5, 6 ],
     [ 6, 7 ],
     [ 7, 8 ],
     [ 8, 9 ],
     [ 9, 10 ] ] }

Install

npm install simplify-planar-graph

API

`require("simplify-planar-graph")(edges, positions, tolerance)`

Simplies a planar graph to a given tolerance

edges are the edges of the graph represented by pairs of vertex indices
positions is a list of vertex coordinates encoded as an array of 2D arrays
tolerance controls the target aspect ratio of the corners of the mesh

Returns A new planar graph encoded as a JSON object with two properties:

edges is an array of edges encoded as pairs of indices
positions is an array of positions for the simplicial complex

Note The current implementation does not detect the removal of features which cross existing line segments. Picking a high tolerance value may result in destroying the planarity of the resulting graph. Eventually if it becomes a priority I may go back and implement code to detect and handle these cases.