D3 Examples - N-Body Problem

xxxxxxxxxx
 
<!DOCTYPE html>
<meta charset="utf-8">
<style>
​
body {
  background: #333;
}
​
</style>
<canvas width="2304" height="1440"></canvas>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>
​
var canvas = document.querySelector("canvas"),
    context = canvas.getContext("2d"),
    width = canvas.width,
    height = canvas.height;
  
context.scale(2,2)
​
var n = 200,
    tau = 2 * Math.PI,
    nodes = d3.range(n).map(function() { return {radius: Math.random() * 8 + 2}; });
​
var force = d3.layout.force()
    .charge(0.5)
    .gravity(0)
    .friction(1)
    .nodes(nodes)
    .size([width, height])
    .start();
​
context.fillStyle = "#fff";
​
force.on("tick", function(e) {
  context.clearRect(0, 0, width, height);
​
  var q = d3.geom.quadtree(nodes), node, i;
  for (i = 1; i < n; ++i) q.visit(collide(nodes[i]));
​
  for (i = 1; i < n; ++i) {
    node = nodes[i];
    context.beginPath();
    context.arc(node.x, node.y, node.radius, 0, tau);
    context.fill();
  }
​
  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 * 2);
        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>
​
    