n-body-pairs

n-body-pairs

Given a collection of spheres with equal radii, find all pairwise intersections.

Usage

First install using npm:

npm install n-body-pairs

Then use it as follows:

//Load the library, allocate initial data structure for searching in 3-dimensions with initial reserve capacity of 1000 points
var nbp = require("n-body-pairs")(3, 1000)

//Create some points
var points = [
  [0, 0, 0],
  [1, 0, 0],
  [0, 1, 0],
  [0, 0, 100000000],
  [0, 0, 100000001]
]

//Report all pairs of points which are within 0.6 units of eachother
nbp(points, 0.6, function(i,j,d2) {
    console.log("Overlap ("+i+","+j+") Distance=", Math.sqrt(d2), "Positions=", points[i], points[j])
})
//Prints:
//
//  Overlap (0,3) Distance= 1 Positions= [ 0, 0, 0 ] [ 0, 0, 1 ]
//  Overlap (2,0) Distance= 1 Positions= [ 0, 1, 0 ] [ 0, 0, 0 ]
//  Overlap (1,0) Distance= 1 Positions= [ 1, 0, 0 ] [ 0, 0, 0 ]
//  Overlap (4,5) Distance= 1 Positions= [ 0, 0, 100000000 ] [ 0, 0, 100000001 ]
//

var nbp = require("n-body-pairs")(dimension, capacity)

Allocates a data structure for performing n-body neighborhood queries.

• dimension is the dimension of the space to search in (default 2)
• capacity is the initial size of the data structure to reserve (default 1000)

Storage Complexity: O(capacity * 2^dimension)

nbp(points, radius, callback(a,b,d2))

Computes all pairwise overlaps. If the data structure does not have sufficient capacity, it is resized.

• points is an array of points
• radius is the radius of the overlap query
• callback(a,b,d2) is a function which is called on each pair of overlapping points. If it returns a truthy value, then iteration is terminated. The parameters are as follows:
  • a index of first point
  • b index of second point
  • d2 squared distance between a and b

Time Complexity: O(points.length * dimension * 2^dimension * log(points.length) + number of intersections)

nbp.capacity

Returns the size of the data structure (set to 0 to free memory. Set to change the reserve capacity of the data structure.

Credits

(c) 2013 Mikola Lysenko. BSD License