D3 Examples - Flocking faces

Flocking faces
Playing around with Boids-style flocking. Click to add more, coloring by movement colors each boid by a moving average of its acceleration magnitude.
More boids:
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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8" />
</head>
<body>
  <canvas width="960" height="500"></canvas>
  <canvas width="960" height="500" class="offscreen" style="display: none;"></canvas>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/dat-gui/0.6.5/dat.gui.min.js"></script>
<script src="vec2.js"></script>
<script>
​
var canvas = document.querySelector("canvas"),
    context = canvas.getContext("2d"),
    offscreen = document.querySelector(".offscreen"),
    offscreenContext = offscreen.getContext("2d"),
    gui = new dat.GUI();
​
var width = 960,
    height = 500,
    numBoids = 400,
    flockmateRadius = 107,
    separationDistance = 50,
    maxVelocity = 2,
    separationForce = 0.11,
    alignmentForce = 0.07,
    cohesionForce = 0.08,
    startingPosition = "Phyllotaxis",
    coloring = "By Movement",
    boids;
​
offscreenContext.globalAlpha = 0.65;
​
gui.add(window, "flockmateRadius", 0, 500).step(1);
gui.add(window, "separationDistance", 0, 100).step(1);
gui.add(window, "maxVelocity", 0, 5).step(0.25);
gui.add(window, "cohesionForce", 0, 0.25);
gui.add(window, "alignmentForce", 0, 0.25);
gui.add(window, "separationForce", 0, 0.25);
// gui.add(window, "numBoids", 1, 600).step(1).onChange(restart);
gui.add(window, "startingPosition", ["Random", "CircleIn", "CircleRandom", "Sine", "Phyllotaxis"]).onChange(restart);
gui.add(window, "coloring", ["Rainbow", "By Movement"]);
gui.add(window, "restart");
​
var drawings;
 
var line =  d3.line()
  .x(function(d) { return d.x })
  .y(function(d) { return d.y })
  .curve(d3.curveBasis)
  .context(context)
​
d3.json("complex-faces.json", function(err, data) {
  drawings = data.map(function(d) {
    d.strokes = d.drawing.map(function(s) {
      var points = []
      s[0].forEach(function(x,i) {
        points.push({x: x, y: s[1][i] })
      })
      return points;
    })
    return d;
  })
//   console.log("DRAW", drawings)
​
  restart();
  requestAnimationFrame(tick);
})
​
function tick() {
  if(!drawings) return;
​
  offscreenContext.clearRect(0, 0, width, height);
  offscreenContext.drawImage(canvas, 0, 0, width, height);
  context.clearRect(0, 0, width, height);
  context.drawImage(offscreen, 0, 0, width, height);
​
  boids.forEach(function(b,i){
​
    var forces = {
      alignment: new Vec2(),
      cohesion: new Vec2(),
      separation: new Vec2()
    };
​
    b.acceleration = new Vec2();
​
    boids.forEach(function(b2){
      if (b === b2) return;
​
      var diff = b2.position.clone().subtract(b.position),
          distance = diff.length();
​
      if (distance && distance < separationDistance) {
        forces.separation.add(diff.clone().scaleTo(-1 / distance)).active = true;
      }
​
      if (distance < flockmateRadius) {
        forces.cohesion.add(diff).active = true;
        forces.alignment.add(b2.velocity).active = true;
      }
​
    });
​
​
    for (var key in forces) {
      if (forces[key].active) {
        forces[key].scaleTo(maxVelocity)
          .subtract(b.velocity)
          .truncate(window[key + "Force"]);
        b.acceleration.add(forces[key]);
      }
    }
​
    if (coloring === "By Movement") {
      b.last.push(b.acceleration.length() / (alignmentForce + cohesionForce + separationForce));
      if (b.last.length > 20) {
        b.last.shift();
      }
    }
​
  });
​
  boids.forEach(updateBoid);
  requestAnimationFrame(tick);
​
}
​
function updateBoid(b, i) {
  b.position.add(b.velocity.add(b.acceleration).truncate(maxVelocity));
​
  if (b.position.y > height) {
    b.position.y -= height;
  } else if (b.position.y < 0) {
    b.position.y += height;
  }
​
  if (b.position.x > width) {
    b.position.x -= width;
  } else if (b.position.x < 0) {
    b.position.x += width;
  }
  if(!drawings) return;
    context.save()
  context.beginPath();
  if (coloring === "Rainbow") {
//     context.fillStyle = b.color;
    context.strokeStyle = b.color;
  } else {
//     context.fillStyle = d3.interpolateWarm(d3.mean(b.last));
    context.strokeStyle = d3.interpolateWarm(d3.mean(b.last));
  }
//   context.arc(b.position.x, b.position.y, 2, 0, 2 * Math.PI);
  context.lineWidth = 5
​
  context.translate(b.position.x, b.position.y)
  context.scale(0.1, 0.1)
  drawings[i].strokes.forEach(function(s) {
    
    line(s)
  })
  context.stroke();
  context.restore()
}
​
function initializeRandom() {
  return d3.range(numBoids).map(function(d, i){
    return {
      position: new Vec2(Math.random() * width, Math.random() * height),
      velocity: randomVelocity()
    };
  });
}
​
function initializePhyllotaxis() {
  return d3.range(numBoids).map(function(d, i){
    var θ = Math.PI * i * (Math.sqrt(5) - 1),
        r = Math.sqrt(i) * 200 / Math.sqrt(numBoids);
​
    return {
      position: new Vec2(width / 2 + r * Math.cos(θ),height / 2 - r * Math.sin(θ)),
      velocity: radialVelocity(i / numBoids)
    };
  });
}
​
function initializeSine() {
  return d3.range(numBoids).map(function(i){
    var angle = 2 * Math.PI * i / numBoids,
        x = width * i / numBoids,
        y = height / 2 + Math.sin(angle) * height / 4;
​
    return {
      position: new Vec2(x, y),
      velocity: radialVelocity(i / numBoids)
    };
  });
}
​
function initializeCircleIn() {
  return d3.range(numBoids).map(function(i){
    var angle = i * 2 * Math.PI / numBoids,
        x = 200 * Math.sin(angle),
        y = 200 * Math.cos(angle);
​
    return {
      position: new Vec2(x + width / 2, y + height / 2),
      velocity: new Vec2(-x, -y).scale(maxVelocity)
    };
  });
}
​
function initializeCircleRandom() {
  return d3.range(numBoids).map(function(i){
    var angle = i * 2 * Math.PI / numBoids,
        x = 200 * Math.sin(angle),
        y = 200 * Math.cos(angle);
​
    return {
      position: new Vec2(x + width / 2, y + height / 2),
      velocity: randomVelocity().scale(maxVelocity)
    };
  });
}
​
function randomVelocity() {
  return new Vec2(1 - Math.random() * 2, 1 - Math.random() * 2).scale(maxVelocity);
}
​
function radialVelocity(p) {
  return new Vec2(Math.sin(2 * Math.PI * p), Math.cos(2 * Math.PI * p)).scale(maxVelocity);
}
​
function restart() {
  offscreenContext.clearRect(0, 0, width, height);
  context.clearRect(0, 0, width, height);
  boids = window["initialize" + startingPosition]();
  boids.forEach(function(b, i){
    b.color = d3.interpolateRainbow(i / numBoids);
    b.last = [];
  });
}
​
</script>
​
    