D3 Examples - shape packing

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<!DOCTYPE html>
<meta charset='utf-8'>
<body>
<script src='https://d3js.org/d3.v3.js'></script>
<script>
​
var w = 700,
    h = 700;
​
var beaker_w = 250,
    beaker_h = beaker_w * 1.3420289855072465,
    beaker_area = beaker_w * beaker_h,
    padding = 2;
​
function get_area(circle_obj) { return Math.PI * circle_obj.r * circle_obj.r; }
​
var dead = [],
    n = 0;
​
while (d3.sum(dead, get_area) < beaker_area * 0.6) {
    dead.push({
        date: n, 
        x: w/2 + (Math.random() > 0.5 ? Math.random() * 50 : Math.random() * -50),
        y: h/8 + (Math.random() > 0.5 ? Math.random() * 50 : Math.random() * -50) - 175,
        r: Math.random() * 30 + 8
    });
​
    n += 1;
}
​
var living = [];
​
var svg = d3.select("body").append('svg')
    .attr('width', w)
    .attr('height', h);
​
svg.on('click', function () { console.log(d3.mouse(this)); })
​
// put beaker on screen
svg.append('image')
    .attr({
        'xlink:href': 'beaker.svg',
        x: w / 2 - beaker_w / 2,
        y: h - beaker_h,
        width: beaker_w,
        height: beaker_h
    })
    .style('opacity', 0.8);
​
var shape_map = {0: 'cross', 1: 'hexagon', 2: 'circle', 3: 'diamond', 4: 'x'};
var opacity = d3.scale.linear()
    .domain([0, 1])
    .range([0.1, 1])
​
function get_shape() {
    var n = Math.floor(Math.random() * 5);
    return shape_map[n] + '.svg';
}
​
svg.selectAll('.shape')
    .data(dead)
    .enter()
    .append('image')
    .attr({
        class: 'shape',
        'xlink:href': function () { return get_shape(); },
        x: function (d) { return d.x - d.r; },
        y: function (d) { return d.y - d.r; },
        width: function (d) { return d.r * 2; },
        height: function (d) { return d.r * 2; }
    })
    .style('opacity', function () { return opacity(Math.random() / 3); });
​
var force = d3.layout.force()
    .size([w, h])
    .gravity(0)
    .charge(0)
    .friction(0.8)
    .nodes(living);
​
force.on("tick", function(e) {
    var q = d3.geom.quadtree(living),
        i = 0,
        n = living.length;
​
    while (++i < n) q.visit(collide(living[i]));
    living.forEach(move_towards_center(e.alpha));
​
svg.selectAll('.shape')
    .attr("x", function (d) { return d.x - d.r; })
    .attr("y", function (d) { return d.y - d.r; });
});
​
var center = {x: w / 2, y: h};
​
function move_towards_center(alpha) {
    var k = alpha * 0.05;
​
    return function(d, i) {
        var new_x = d.x + (center.x - d.x) * k;
        var min_x = w/2 - beaker_w/2 + d.r + padding,
            max_x = w/2 + beaker_w/2 - d.r - padding;
​
        var new_y = d.y + (center.y - d.y) * k;
        var min_y = 0,//h - beaker_h + d.r + padding,
            max_y = h - d.r - padding - 4;
​
        d.x = Math.min(max_x, Math.max(new_x, min_x));
        d.y = Math.min(max_y, Math.max(new_y, min_y));
    }
}
​
function collide(node) {
    var r = node.r + 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.r + quad.point.r + padding;
         
            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;
    };
}
​
var started = false;
​
function f() {
    var current = dead.pop();
    living.push(current);
    force.start();
}
​
var n_dead = dead.length,
    i = 0,
    delay = 0;
​
while (i < n_dead) {
    setTimeout(f, delay)
    delay += 600;
    i += 1;
}
​
</script>
    