Boolean operations for planar straight line graphs
MIT License
Compute a regularized Boolean operation between the interiors of two planar straight line graphs.
Here is a simple example showing how to use this module to compute the intersection of two PSLGs:
//Load the module
var overlay = require('overlay-pslg')
//Red PSLG - Define a triangle
var redPoints = [
[0.5, 0.25],
[0.25, 0.5],
[0.75, 0.75]
]
var redEdges = [ [0,1], [1,2], [2,0] ]
//Blue PSLG - Define a square
var bluePoints = [
[0.25, 0.25],
[0.25, 0.6],
[0.6, 0.6],
[0.6, 0.25]
]
var blueEdges = [ [0,1], [1,2], [2,3], [3,0] ]
//Construct intersection
console.log(overlay(redPoints, redEdges, bluePoints, blueEdges, 'and'))
The result of this module is the following JSON:
{ points:
[ [ 0.6, 0.6 ],
[ 0.44999999999999996, 0.6 ],
[ 0.25, 0.5 ],
[ 0.5, 0.25 ],
[ 0.6, 0.44999999999999996 ] ],
red: [ [ 1, 2 ], [ 2, 3 ], [ 3, 4 ] ],
blue: [ [ 0, 1 ], [ 0, 4 ] ] }
We can visualize this result as follows:
To install this module, you can use npm. The command is as follows:
npm i overlay-pslg
It works in any reasonable CommonJS environment like node.js. If you want to use it in a browser, you should use browserify.
require('overlay-pslg')(redPoints, redEdges, bluePoints, blueEdges[, op])
Computes a Boolean operation between two planar straight line graphs.
redPoints, redEdges
are the points and edges of the first complexbluePoints, blueEdges
are the points and edges of the second complexop
the boolean operator to compute (Default "xor"
). Possible values include:
"xor"
- computes the symmetric difference of red
and blue
"and"
- computes the intersection of red
and blue
"or"
- computes the union of red
and blue
"sub"
- comutes the set difference, blue-red
"rsub"
- comutes the set difference, red-blue
Returns An object encoding a planar straight line graph with the edges partitioned into two sets:
points
are the points of the combined cell complexred
are the edges in the resulting pslg coming from the red graphblue
are the edges in the resulting pslg coming from the blue graphNote The interiors of red and blue are computed using the same algorithm as cdt2d
, which is it counts the parity of the path with the fewest number of boundary crossings for each point. Even parity points are in the exterior, odd parity in the interior.
(c) 2015 Mikola Lysenko. MIT License