dannyko/index.html

## index.html
<!DOCTYPE html>
<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
    <script src="http://d3js.org/d3.v3.min.js"></script>
    <link type="text/css" rel="stylesheet" href="style.css"/>
    <style type="text/css">

circle {
  stroke: #000;
  stroke-opacity: .5;
}

    </style>
  </head>
  <body>
    <div id="body">
      <div id="footer">
        Collision Detection
        <div class="hint">move the mouse to repel nodes</div>
      </div>
    </div>
    <script type="text/javascript">

var w = 1280,
    h = 800;

var nodes = d3.range(200).map(function() { return {radius: Math.random() * 12 + 4}; }),
    color = d3.scale.category10();

var force = d3.layout.force()
    .gravity(0.05)
    .charge(function(d, i) { return i ? 0 : -2000; })
    .nodes(nodes)
    .size([w, h]);

var root = nodes[0];
root.radius = 0;
root.fixed = true;

force.start();

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

svg.selectAll("circle")
    .data(nodes.slice(1))
  .enter().append("svg:circle")
    .attr("r", function(d) { return d.radius - 2; })
    .style("fill", function(d, i) { return color(i % 3); });

force.on("tick", function(e) {
  var q = d3.geom.quadtree(nodes),
      i = 0,
      n = nodes.length;

  while (++i < n) {
    q.visit(collide(nodes[i]));
  }

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

svg.on("mousemove", function() {
  var p1 = d3.mouse(this);
  root.px = p1[0];
  root.py = p1[1];
  force.resume();
});

function collide(node) {
  var r = node.radius + 16,
      nx1 = node.x - r,
      nx2 = node.x + r,
      ny1 = node.y - r,
      ny2 = node.y + r;
  return function(quad, x1, y1, x2, y2) {
    if (quad.point && (quad.point !== node)) {
      var x = node.x - quad.point.x,
          y = node.y - quad.point.y,
          l = Math.sqrt(x * x + y * y),
          r = node.radius + quad.point.radius;
      if (l < r) {
        l = (l - r) / l * .5;
        node.x -= x *= l;
        node.y -= y *= l;
        quad.point.x += x;
        quad.point.y += y;
      }
    }
    return x1 > nx2
        || x2 < nx1
        || y1 > ny2
        || y2 < ny1;
  };
}

    </script>
  </body>
</html>
	<!DOCTYPE html>
	<html>
	<head>
	<meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
	<script src="http://d3js.org/d3.v3.min.js"></script>
	<link type="text/css" rel="stylesheet" href="style.css"/>
	<style type="text/css">

	circle {
	stroke: #000;
	stroke-opacity: .5;
	}

	</style>
	</head>
	<body>
	<div id="body">
	<div id="footer">
	Collision Detection
	<div class="hint">move the mouse to repel nodes</div>
	</div>
	</div>
	<script type="text/javascript">

	var w = 1280,
	h = 800;

	var nodes = d3.range(200).map(function() { return {radius: Math.random() * 12 + 4}; }),
	color = d3.scale.category10();

	var force = d3.layout.force()
	.gravity(0.05)
	.charge(function(d, i) { return i ? 0 : -2000; })
	.nodes(nodes)
	.size([w, h]);

	var root = nodes[0];
	root.radius = 0;
	root.fixed = true;

	force.start();

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

	svg.selectAll("circle")
	.data(nodes.slice(1))
	.enter().append("svg:circle")
	.attr("r", function(d) { return d.radius - 2; })
	.style("fill", function(d, i) { return color(i % 3); });

	force.on("tick", function(e) {
	var q = d3.geom.quadtree(nodes),
	i = 0,
	n = nodes.length;

	while (++i < n) {
	q.visit(collide(nodes[i]));
	}

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

	svg.on("mousemove", function() {
	var p1 = d3.mouse(this);
	root.px = p1[0];
	root.py = p1[1];
	force.resume();
	});

	function collide(node) {
	var r = node.radius + 16,
	nx1 = node.x - r,
	nx2 = node.x + r,
	ny1 = node.y - r,
	ny2 = node.y + r;
	return function(quad, x1, y1, x2, y2) {
	if (quad.point && (quad.point !== node)) {
	var x = node.x - quad.point.x,
	y = node.y - quad.point.y,
	l = Math.sqrt(x * x + y * y),
	r = node.radius + quad.point.radius;
	if (l < r) {
	l = (l - r) / l * .5;
	node.x -= x *= l;
	node.y -= y *= l;
	quad.point.x += x;
	quad.point.y += y;
	}
	}
	return x1 > nx2
	\|\| x2 < nx1
	\|\| y1 > ny2
	\|\| y2 < ny1;
	};
	}

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