Monica Monica - 1 month ago 7
Javascript Question

After a few clicks the animation freezes, why?

I have the following code, which I took and modify from here

Here is my jsfiddle in action

I am currently developing a user interaction that needs these bubbles, exactly 5 bubbles that gravitate to the center of the screen. The thing is that I know how many times a user will click on each of these bubbles. The thing I noticed is that at some point the bubbles keep growing but the collision among them will stop working.

Here you can see the code that modify:

var width = 500,
height = 500,
padding = 1.5, // separation between same-color circles
clusterPadding = 4, // separation between different-color circles
maxRadius = 40;

var n = 5, // total number of circles
m = 1; // number of distinct clusters

var color = d3.scale.category10()
.domain(d3.range(m));

// The largest node for each cluster.
var clusters = new Array(m);

var nodes = d3.range(n).map(function() {
var i = Math.floor(Math.random() * m),
//r = Math.sqrt((i + 1) / m * -Math.log(Math.random())) * maxRadius,
r = maxRadius,
d = {cluster: i, radius: r};
if (!clusters[i] || (r > clusters[i].radius)) clusters[i] = d;
return d;
});

// Use the pack layout to initialize node positions.
d3.layout.pack()
.sort(null)
.size([width, height])
.children(function(d) { return d.values; })
.value(function(d) { return d.radius * d.radius; })
.nodes({values: d3.nest()
.key(function(d) { return d.cluster; })
.entries(nodes)});

var force = d3.layout.force()
.nodes(nodes)
.size([width, height])
.gravity(.02)
.charge(0)
.on("tick", tick)
.start();

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

var node = svg.selectAll("circle")
.data(nodes)
.enter().append("circle")
.style("fill", function(d) { return color(d.cluster); })
.on("click", function(d) {
d.radius *= 1.1;
d3.select(this).attr("r", d.radius);
})
.call(force.drag);

node.transition()
.duration(750)
.delay(function(d, i) { return i * 5; })
.attrTween("r", function(d) {
var i = d3.interpolate(0, d.radius);
return function(t) { return d.radius = i(t); };
});

function tick(e) {
node
.each(cluster(10 * e.alpha * e.alpha))
.each(collide(.5))
.attr("cx", function(d) { return d.x; })
.attr("cy", function(d) { return d.y; });
}

// Move d to be adjacent to the cluster node.
function cluster(alpha) {
return function(d) {
var cluster = clusters[d.cluster];
if (cluster === d) return;
var x = d.x - cluster.x,
y = d.y - cluster.y,
l = Math.sqrt(x * x + y * y),
r = d.radius + cluster.radius;
if (l != r) {
l = (l - r) / l * alpha;
d.x -= x *= l;
d.y -= y *= l;
cluster.x += x;
cluster.y += y;
}
};
}

// Resolves collisions between d and all other circles.
function collide(alpha) {
var quadtree = d3.geom.quadtree(nodes);
return function(d) {
var r = d.radius + maxRadius + Math.max(padding, clusterPadding),
nx1 = d.x - r,
nx2 = d.x + r,
ny1 = d.y - r,
ny2 = d.y + r;
quadtree.visit(function(quad, x1, y1, x2, y2) {
if (quad.point && (quad.point !== d)) {
var x = d.x - quad.point.x,
y = d.y - quad.point.y,
l = Math.sqrt(x * x + y * y),
r = d.radius + quad.point.radius + (d.cluster === quad.point.cluster ? padding : clusterPadding);
if (l < r) {
l = (l - r) / l * alpha;
d.x -= x *= l;
d.y -= y *= l;
quad.point.x += x;
quad.point.y += y;
}
}
return x1 > nx2 || x2 < nx1 || y1 > ny2 || y2 < ny1;
});
};
}

Answer

That behaviour you described happens because the force has ended. So, the simplest situations is reheating the force at every click:

.on("click", function(d) {
    d.radius *= 1.1;
    d3.select(this).attr("r", d.radius);
    force.resume();
})

Here, force.resume():

Sets the cooling parameter alpha to 0.1. This method sets the internal alpha parameter to 0.1, and then restarts the timer. Typically, you don't need to call this method directly; it is called automatically by start. It is also called automatically by drag during a drag gesture.

Here is your updated fiddle: https://jsfiddle.net/usb7nhfm/