Connected Particles III

Fork of mbostock's block /mbostock/280d83080497c8c13152.

<!DOCTYPE html>
<meta charset="utf-8">
<canvas width="960" height="500"></canvas>
<script>

/* https://github.com/d3/d3-timer Copyright 2015 Mike Bostock */
"undefined"==typeof requestAnimationFrame&&(requestAnimationFrame="undefined"!=typeof window&&(window.msRequestAnimationFrame||window.mozRequestAnimationFrame||window.webkitRequestAnimationFrame||window.oRequestAnimationFrame)||function(e){return setTimeout(e,17)}),function(e,n){"object"==typeof exports&&"undefined"!=typeof module?n(exports):"function"==typeof define&&define.amd?define(["exports"],n):n(e.timer={})}(this,function(e){"use strict";function n(){r=m=0,c=1/0,t(u())}function t(e){if(!r){var t=e-Date.now();t>24?c>e&&(m&&clearTimeout(m),m=setTimeout(n,t),c=e):(m&&(m=clearTimeout(m),c=1/0),r=requestAnimationFrame(n))}}function i(e,n,i){i=null==i?Date.now():+i,null!=n&&(i+=+n);var o={callback:e,time:i,flush:!1,next:null};a?a.next=o:f=o,a=o,t(i)}function o(e,n,t){t=null==t?Date.now():+t,null!=n&&(t+=+n),l.callback=e,l.time=t}function u(e){e=null==e?Date.now():+e;var n=l;for(l=f;l;)e>=l.time&&(l.flush=l.callback(e-l.time,e)),l=l.next;l=n,e=1/0;for(var t,i=f;i;)i.flush?i=t?t.next=i.next:f=i.next:(i.time<e&&(e=i.time),i=(t=i).next);return a=t,e}var a,m,r,f,l,c=1/0;e.timer=i,e.timerReplace=o,e.timerFlush=u});

var canvas = document.querySelector("canvas"),
    context = canvas.getContext("2d"),
    width = canvas.width,
    height = canvas.height,
    radius = 2.5,
    minDistance = 40,
    maxDistance = 60,
    minDistance2 = minDistance * minDistance,
    maxDistance2 = maxDistance * maxDistance;

var tau = 2 * Math.PI,
    n = 200,
    particles = new Array(n);

for (var i = 0; i < n; ++i) {
  particles[i] = {
    x: Math.random() * width,
    y: Math.random() * height,
    vx: 0,
    vy: 0
  };
}

timer.timer(function(elapsed) {
  context.save();
  context.clearRect(0, 0, width, height);

for (var i = 0; i < n; ++i) {
    var p = particles[i];
    p.x += p.vx; if (p.x < -maxDistance) p.x += width + maxDistance * 2; else if (p.x > width + maxDistance) p.x -= width + maxDistance * 2;
    p.y += p.vy; if (p.y < -maxDistance) p.y += height + maxDistance * 2; else if (p.y > height + maxDistance) p.y -= height + maxDistance * 2;
    p.vx += 0.2 * (Math.random() - .5) - 0.01 * p.vx;
    p.vy += 0.2 * (Math.random() - .5) - 0.01 * p.vy;
    context.beginPath();
    context.arc(p.x, p.y, radius, 0, tau);
    context.fill();
  }

for (var i = 0; i < n; ++i) {
    for (var j = i + 1; j < n; ++j) {
      var pi = particles[i],
          pj = particles[j],
          dx = pi.x - pj.x,
          dy = pi.y - pj.y,
          d2 = dx * dx + dy * dy;
      if (d2 < maxDistance2) {
        context.globalAlpha = d2 > minDistance2 ? (maxDistance2 - d2) / (maxDistance2 - minDistance2) : 1;
        context.beginPath();
        context.moveTo(pi.x, pi.y);
        context.lineTo(pj.x, pj.y);
        context.stroke();
      }
    }
  }

context.restore();
});

</script>