Force-Directed Tree, fixing angles [UNLISTED]

This randomly-generated tree is positioned using a force simulation.

forked from mbostock's block: Force-Directed Tree

<!DOCTYPE html>
<meta charset="utf-8">
<canvas width="960" height="300"></canvas>
<script src="https://d3js.org/d3.v4.0.0-alpha.49.min.js"></script>
<script>
var nodes = d3.range(400).map(function(i) {
  return {
    index: i
  };
});

var links = d3.range(nodes.length - 1).map(function(i) {
  return {
    source: Math.floor(Math.sqrt(i)),
    target: i + 1,
  };
});

var simulation = d3.forceSimulation(nodes)
    .force("charge", d3.forceManyBody())
    .force("link", d3.forceLink(links).distance(20).strength(1))
    .force("x", d3.forceX())
    .force("y", d3.forceY())
    .force("f", f(links))
    .on("tick", ticked);

var canvas = document.querySelector("canvas"),
    context = canvas.getContext("2d"),
    width = canvas.width,
    height = canvas.height;

d3.select(canvas)
    .call(d3.drag()
        .container(canvas)
        .subject(dragsubject)
        .on("start", dragstarted)
        .on("drag", dragged)
        .on("end", dragended));

function ticked() {
  context.clearRect(0, 0, width, height);
  context.save();
  context.translate(width / 2, height / 2);

context.beginPath();
  links.forEach(drawLink);
  context.strokeStyle = "#aaa";
  context.stroke();

context.beginPath();
  nodes.forEach(drawNode);
  context.fill();
  context.strokeStyle = "#fff";
  context.stroke();

context.restore();
}

function dragsubject() {
  return simulation.find(d3.event.x - width / 2, d3.event.y - height / 2);
}

function dragstarted() {
  if (!d3.event.active) simulation.alphaTarget(0.3).restart()
  simulation.fix(d3.event.subject);
}

function dragged() {
  simulation.fix(d3.event.subject, d3.event.x, d3.event.y);
}

function dragended() {
  if (!d3.event.active) simulation.alphaTarget(0);
  simulation.unfix(d3.event.subject);
}

function drawLink(d) {
  context.moveTo(d.source.x, d.source.y);
  context.lineTo(d.target.x, d.target.y);
}

function drawNode(d) {
  context.moveTo(d.x + 3, d.y);
  context.arc(d.x, d.y, 3, 0, 2 * Math.PI);
}

</script>

https://d3js.org/d3.v4.0.0-alpha.49.min.js