Shape Tweening

.block

license: gpl-3.0

README.md

See also the linear path tweening example.

california.json

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index.html

<!DOCTYPE html>
<meta charset="utf-8">
<style>

path {
  fill: #ccc;
  stroke: #000;
}

</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>

var width = 960,
    height = 500;

var projection = d3.geo.albers()
    .rotate([120, 0])
    .center([0, 37.7])
    .scale(2700);

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

d3.json("california.json", function(polygon) {
  var coordinates0 = polygon.coordinates[0].map(projection),
      coordinates1 = circle(coordinates0),
      path = svg.append("path"),
      d0 = "M" + coordinates0.join("L") + "Z",
      d1 = "M" + coordinates1.join("L") + "Z";

  loop();

  function loop() {
    path
        .attr("d", d0)
      .transition()
        .duration(5000)
        .attr("d", d1)
      .transition()
        .delay(5000)
        .attr("d", d0)
        .each("end", loop);
  }
});

function circle(coordinates) {
  var circle = [],
      length = 0,
      lengths = [length],
      polygon = d3.geom.polygon(coordinates),
      p0 = coordinates[0],
      p1,
      x,
      y,
      i = 0,
      n = coordinates.length;

  // Compute the distances of each coordinate.
  while (++i < n) {
    p1 = coordinates[i];
    x = p1[0] - p0[0];
    y = p1[1] - p0[1];
    lengths.push(length += Math.sqrt(x * x + y * y));
    p0 = p1;
  }

  var area = polygon.area(),
      radius = Math.sqrt(Math.abs(area) / Math.PI),
      centroid = polygon.centroid(-1 / (6 * area)),
      angleOffset = -Math.PI / 2, // TODO compute automatically
      angle,
      i = -1,
      k = 2 * Math.PI / lengths[lengths.length - 1];

  // Compute points along the circle’s circumference at equivalent distances.
  while (++i < n) {
    angle = angleOffset + lengths[i] * k;
    circle.push([
      centroid[0] + radius * Math.cos(angle),
      centroid[1] + radius * Math.sin(angle)
    ]);
  }

  return circle;
}

</script>

thumbnail.png

Hi! I'm new to javascript and I was curious why this, and often many examples I try, do not seem to work when trying it out. The html page is identical code and I have california.json in the same folder. Any thoughts? Thanks.

I'm guessing you are using Chrome. The file protocol has more restricted origin rules (at least by default). Try viewing the demo from an apache server running on localhost.

See: http://stackoverflow.com/questions/6060786/file-url-cross-domain-issue-in-chrome-unexpected

@mbostock fixed the TODO in line 73. You may merge with https://gist.github.com/ge045/2e7de433f1d1d5948bbd/revisions