Modified force-multi-foci.html to add a convex hull

<!DOCTYPE html>
<html>
  <head>
    <title>Force-Directed Layout with Convex Hull</title>
    <script src="https://cdn.jsdelivr.net/npm/d3@2.7.4/d3.js"></script>
 </head>
  <body>
    <div id="chart"></div>
    <script type="text/javascript">

var w = 960,
    h = 500,
    fill = d3.scale.category10(),
    nodes = d3.range(100).map(Object);

var vis = d3.select("#chart").append("svg")
    .attr("width", w)
    .attr("height", h);

vis.append("path")
      .style("fill", "#ccf")
      .style("stroke", "#ccf")
      .style("stroke-width", 20);

var force = d3.layout.force()
    .nodes(nodes)
    .links([])
    .size([w, h])
    .start();

vis.style("opacity", 1e-6)
  .transition()
    .duration(1000)
    .style("opacity", 1);

force.on("tick", function(e) {

// Push different nodes in different directions for clustering.
  var k = 6 * e.alpha;
  nodes.forEach(function(o, i) {
    o.x += i & 2 ? k : -k;
    o.y += i & 1 ? k : -k;
  });

node.attr("cx", function(d) { return d.x; })
      .attr("cy", function(d) { return d.y; });

vis.selectAll("path")
      .data([d3.geom.hull(nodes.map(function(d) { return [ d.x, d.y ]; }))])
      .attr("d", function(d) { return "M" + d.join("L") + "Z"; });
});

d3.select("body").on("click", function() {
  nodes.forEach(function(o, i) {
    o.x += (Math.random() - .5) * 40;
    o.y += (Math.random() - .5) * 40;
  });
  force.resume();
});

</script>
  </body>
</html>

Modified http://mbostock.github.com/d3/d3.js?2.7.4 to a secure url

https://mbostock.github.com/d3/d3.js?2.7.4