Interrupted Projection Transitions

Interrupted projections using the geo.projection D3 plugin.

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

body {
  height: 500px;
  position: relative;
  width: 960px;
  font-family: sans-serif;
}

#projection-menu {
  position: absolute;
  right: 10px;
  top: 10px;
}

#gores {
  position: absolute;
  left: 10px;
  top: 10px;
}

.background {
  fill: #a4bac7;
}

.foreground {
  fill: none;
  stroke: #333;
  stroke-width: 1.5px;
}

.graticule {
  fill: none;
  stroke: #fff;
  stroke-width: .5px;
}

.graticule:nth-child(2n) {
  stroke-dasharray: 2,2;
}

.land {
  fill: #d7c7ad;
  stroke: #766951;
}

.boundary {
  fill: none;
  stroke: #a5967e;
}

</style>
<body>
<select id="projection-menu"></select>
<input type="range" id="gores" step="1" min="1" max="12" value="3">
<script src="https://d3js.org/d3.v3.min.js"></script>
<script src="https://cdn.jsdelivr.net/gh/d3/d3-plugins/geo/projection/projection.js"></script>
<script>

var π = Math.PI;

var width = 960,
    height = 500;

var projection;

var interrupt, x = [], y;

var path = d3.geo.path();

var graticule = d3.geo.graticule();

function lobes(n) {
  var dλ = (180 - -180) / n;
  return {
    type: "Polygon",
    coordinates: [hemilobes(n, -180, 180, 0, 90).concat(hemilobes(n, 180, -180, 0, -90))].map(resample),
    properties: {interruptions: d3.range(-180, 180 + dλ / 2, dλ)}
  };
}

function hemilobes(n, λ0, λ1, φ0, φ1) {
  var d = [],
      dλ = (λ1 - λ0) / n,
      δ = dλ / 1e6;
  λ0 += δ;
  for (var i = 0; i < n; i++) {
    d.push([λ0, φ0], [λ0, φ1], [λ0 += dλ - 2 * δ, φ1], [λ0, φ0]);
    λ0 += 2 * δ;
  }
  return d;
}

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

var clipPath = svg.append("defs").append("clipPath")
    .attr("id", "clip").append("path");

var background = svg.append("path")
    .attr("class", "background");

var graticules = svg.selectAll(".graticule")
    .data(graticule.lines)
  .enter().append("path")
    .attr("class", "graticule");

var foreground = svg.append("path")
    .attr("class", "foreground");

d3.select("#gores")
    .on("change", function() {
      gores();
      svg.selectAll("path").attr("d", path);
    });

function gores() {
  var n = +d3.select("#gores").property("value");
  d3.select("#gores-output").property("value", n);
  interrupt = lobes(n);
  x = interrupt.properties.interruptions;
  y = x.map(function(x) { return projection([x, 0]); });
  path.projection(goreProjection());

clipPath.datum(interrupt);
  background.datum(interrupt);
  foreground.datum(interrupt);
}

d3.json("/mbostock/3682676/example/readme-boundaries.json", function(err, collection) {
  svg.insert("g", ".graticule")
      .attr("class", "boundary")
      .attr("clip-path", "url(#clip)")
    .selectAll("path")
      .data(collection.geometries)
    .enter().append("path")
      .attr("d", path);
});

d3.json("/mbostock/3682676/example/readme-land.json", function(err, collection) {
  svg.insert("g", ".graticule,.boundary")
      .attr("class", "land")
      .attr("clip-path", "url(#clip)")
    .selectAll("path")
      .data(collection.geometries)
    .enter().append("path")
      .attr("d", path);
});

var options = [
  {name: "Aitoff", projection: d3.geo.aitoff()},
//  {name: "Albers", projection: d3.geo.albers().scale(145).parallels([20, 50]).origin([0, 0]).translate([width * .500, height * .750])},
//  {name: "Bonne", projection: d3.geo.bonne().scale(120).translate([width * .500, height * .425])},
//  {name: "Collignon", projection: d3.geo.collignon().scale(93)},
  {name: "Eckert I", projection: d3.geo.eckert1().scale(165)},
  {name: "Eckert II", projection: d3.geo.eckert2().scale(165)},
  {name: "Eckert III", projection: d3.geo.eckert3().scale(180)},
  {name: "Eckert IV", projection: d3.geo.eckert4().scale(180)},
  {name: "Eckert V", projection: d3.geo.eckert5().scale(170)},
  {name: "Eckert VI", projection: d3.geo.eckert6().scale(170)},
//  {name: "Equirectangular (Plate Carrée)", projection: d3.geo.equirectangular().scale(950)},
//  {name: "Hammer", projection: d3.geo.hammer().scale(165)},
  {name: "Goode Homolosine", projection: d3.geo.homolosine()},
  {name: "Kavrayskiy VII", projection: d3.geo.kavrayskiy7()},
//  {name: "Lambert cylindrical equal-area", projection: d3.geo.cylindricalEqualArea()},
  {name: "Larrivée", projection: d3.geo.larrivee().scale(95)},
//  {name: "Mercator", projection: d3.geo.mercator().scale(490)},
//  {name: "Miller", projection: d3.geo.miller().scale(100)},
  {name: "Mollweide", projection: d3.geo.mollweide().scale(165)},
  {name: "Nell–Hammer", projection: d3.geo.nellHammer()},
  {name: "Polyconic", projection: d3.geo.polyconic().scale(100)},
  {name: "Robinson", projection: d3.geo.robinson()},
  {name: "Sinusoidal", projection: d3.geo.sinusoidal()},
  {name: "van der Grinten", projection: d3.geo.vanDerGrinten().scale(75)},
  {name: "Wagner VI", projection: d3.geo.wagner6()},
  {name: "Winkel Tripel", projection: d3.geo.winkel3()}
];

var interval = setInterval(loop, 1500),
    i = 0,
    n = options.length - 1;

var menu = d3.select("#projection-menu")
    .on("change", change);

menu.selectAll("option")
    .data(options)
  .enter().append("option")
    .text(function(d) { return d.name; });

function loop() {
  var j = Math.floor(Math.random() * n);
  menu.property("selectedIndex", i = j + (j >= i));
  update(options[i]);
}

function change() {
  clearInterval(interval);
  update(options[this.selectedIndex]);
}

function update(option) {
  projection = option.projection;
  gores();
  svg.selectAll("path").transition()
      .duration(750)
      .attr("d", path);
}

loop();

</script>

Modified http://d3js.org/d3.v3.min.js to a secure url

Updated missing url https://raw.github.com/d3/d3-plugins/master/geo/projection/projection.js to https://cdn.jsdelivr.net/gh/d3/d3-plugins/geo/projection/projection.js

Changed ajax call from /d/3682676/readme-boundaries.json to /mbostock/3682676/example/readme-boundaries.json.

Changed ajax call from /d/3682676/readme-land.json to /mbostock/3682676/example/readme-land.json.

https://d3js.org/d3.v3.min.js

https://raw.github.com/d3/d3-plugins/master/geo/projection/projection.js