Convex Hull

This example uses d3.geom.hull to compute the 2D convex hull of a set of points. An outer stroke is used to pad the hull. Click to add a new point.

<!DOCTYPE html>
<meta charset="utf-8">
<title>Convex Hull</title>
<style>

rect {
  fill: none;
  pointer-events: all;
}

.hull {
  fill: steelblue;
  stroke: steelblue;
  stroke-width: 32px;
  stroke-linejoin: round;
}

circle {
  fill: white;
  stroke: black;
  stroke-width: 1.5px;
}

</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>

var width = 960,
    height = 500;

var randomX = d3.random.normal(width / 2, 60),
    randomY = d3.random.normal(height / 2, 60),
    vertices = d3.range(100).map(function() { return [randomX(), randomY()]; });

var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height)
    .on("mousemove", function() { vertices[0] = d3.mouse(this); redraw(); })
    .on("click", function() { vertices.push(d3.mouse(this)); redraw(); });

svg.append("rect")
    .attr("width", width)
    .attr("height", height);

var hull = svg.append("path")
    .attr("class", "hull");

var circle = svg.selectAll("circle");

redraw();

</script>

https://d3js.org/d3.v3.min.js