surface-nets
============
Extract a simplicial level set from an ndarray in any dimension using naive surface nets. This module works in both node.js and with browserify!

Example

Here is a 2D example:

``javascript
//Load modules
var surfaceNets = require("surface-nets")
var ndarray = require("ndarray")
var fill = require("ndarray-fill")

//Initialize array to a circle
var array = ndarray(new Float32Array(32*32), [32,32])
fill(array, function(i,j) {
return Math.pow(i-16,2) + Math.pow(j-16,2)
})

//Extract 2D contour (this is all there is to it!)
var complex = surfaceNets(array, 15*15)

//Write SVG image to stdout
var svgFile = ['
complex.cells.forEach(function(cell) {
var p0 = complex.positions[cell[0]]
var p1 = complex.positions[cell[1]]
svgFile.push('')
})
complex.positions.forEach(function(p) {
svgFile.push('')
})
svgFile.push('')
console.log(svgFile.join(""))
`

And here is the output SVG:

This module also works in 3D. Here is an example:

`javascript
//Load modules
var surfaceNets = require("surface-nets")
var ndarray = require("ndarray")
var fill = require("ndarray-fill")
var mat4 = require("gl-matrix").mat4

//Initialize array
var array = ndarray(new Float32Array(323232), [32,32,32])
fill(array, function(i,j,k) {
return Math.pow(i-16,2) + Math.pow(j-16,2) + Math.pow(k-16,2)
})

//Generate surface! (again, just one line)
var complex = surfaceNets(array, 100)

//Render the implicit surface to stdout
console.log('
console.log(require("svg-3d-simplicial-complex")(
complex.cells,
complex.positions, {
view: mat4.lookAt(
mat4.create(),
[32, 32, 32],
[16, 16, 16],
[0,1,0]),
projection: mat4.perspective(mat4.create(),
Math.PI/4.0,
1.0,
0.1,
1000.0),
viewport: [[0,0], [512,512]]
}))
console.log("")
`

And here is the result:

And while it is a bit trivial, you can also generate surfaces in 1D:

`javascript
var surfaceNets = require("surface-nets")
var ndarray = require("ndarray")

console.log(surfaceNets(ndarray([1, -1, 0, 5, -10])))
`

Output:

`javascript
{ positions: [ [ 0.5 ], [ 2 ], [ 3.3333333333333335 ] ],
cells: [ [ 0 ], [ 1 ], [ 2 ] ] }
`

The code should work in 4D and higher dimensions, but this is not well tested and it is harder to visualize. (Also, why would you want to bother!?!)

Install

`
npm install surface-nets
`

API

#### require("surface-nets")(array[,level])
Extracts the level set at level from array as a simplicial complex.

* array is an ndarray
* level is an optional number which determines the level at which the levelset is evaluated (default 0)

Returns An object with a pair of properties representing a simplicial complex:

* positions is an array encoding the positions of the vertices. The coordinates of the positions are with respect to the indices in array.
* cells is an array encoding the cells of the simplicial complex as tuples of indices into the position` array.

Credits

(c) 2014 Mikola Lysenko. MIT License