concaveman
A very fast 2D concave hull algorithm in JavaScript (generates a general outline of a point set).
Usage
var points = [[10, 20], [30, 12.5], ...];
var polygon = concaveman(points);
Signature: concaveman(points[, concavity = 2, lengthThreshold = 0])
points
is an array of [x, y]
points.concavity
is a relative measure of concavity. 1
results in a relatively detailed shape, Infinity
results in a convex hull.
You can use values lower than 1
, but they can produce pretty crazy shapes.lengthThreshold
: when a segment length is under this threshold, it stops being considered for further detalization.
Higher values result in simpler shapes.
Algorithm
The algorithm is based on ideas from the paper A New Concave Hull Algorithm and Concaveness Measure
for n-dimensional Datasets, 2012
by Jin-Seo Park and Se-Jong Oh.
This implementation dramatically improves performance over the one stated in the paper
(O(rn)
, where r
is a number of output points, to O(n log n)
)
by introducing a fast k nearest points to a segment algorithm,
a modification of a depth-first kNN R-tree search using a priority queue.
TypeScript
TypeScript type definitions
are available trough npm install --save @types/concaveman
.
Dependencies