README.md

## README.md

      
        

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              README.md
            
          
        
      
    
  
    The Goode Homolosine projection is available as d3.geo.homolosine in the geo.projection D3 plugin.

  

  

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

.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>
<script src="http://d3js.org/d3.v3.min.js"></script>
<script src="https://raw.github.com/d3/d3-plugins/master/geo/projection/projection.js"></script>
<script>

var π = Math.PI;

var width = 960,
    height = 500;

var projection = d3.geo.homolosine().scale(1).translate([0, 0]);

var graticule = d3.geo.graticule();

// λ0, λ1, central meridian
var goode = [[
  [-180,  -40, -100],
  [ -40,  180,   30]
], [
  [-180, -100, -160],
  [-100,  -20,  -60],
  [ -20,   80,   20],
  [  80,  180,  140]
]];

var interrupt = {
  type: "Polygon",
  coordinates: [hemilobes(goode[0], 0, 90).concat(hemilobes(goode[1], 0, -90).reverse())].map(resample)
}

var y = goode.map(function(d) {
  return d.map(function(d) { return projection([d[2], 0]); });
});

var path = d3.geo.path()
    .projection(d3.geo.projection(function(λ, φ) {
      λ *= 180 / π;
      var j = (φ *= 180 / π) >= 0 ? 0 : 1;
      for (var i = 0; i < goode[j].length; i++) {
        if (λ < goode[j][i][1] + 1e-9) {
          var coordinates = projection([λ - goode[j][i][2], φ]);
          coordinates[0] += y[j][i][0];
          coordinates[1] = -coordinates[1];
          break;
        }
      }
      return coordinates;
    }).translate([width / 2 - .5, height / 2 - .5]));

function hemilobes(interrupts, φ0, φ1) {
  var n = interrupts.length,
      d = [],
      λ,
      δ = 1e-6;
  for (var i = 0; i < n; i++) {
    λ = interrupts[i];
    d.push([λ[0] + δ, φ0], [λ[0] + δ, φ1], [λ[1] - δ, φ1], [λ[1] - δ, φ0]);
  }
  return d;
}

function resample(coordinates) {
  var n = coordinates.length;
  if (!n) return coordinates;
  var samples = 50,
      a = coordinates[0],
      b,
      resampled = [];
  for (var i = 0; ++i < n;) {
    b = coordinates[i];
    dx = (b[0] - a[0]) / samples;
    dy = (b[1] - a[1]) / samples;
    resampled.push(a);
    for (var j = 1; j < samples; j++) {
      resampled.push([dx ? a[0] + j * dx : a[0], dy ? a[1] + j * dy : a[1]]);
    }
    a = b;
  }
  if (b) resampled.push(b);
  return resampled;
}

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")
    .datum(interrupt)
    .attr("d", path);

svg.append("path")
    .datum(interrupt)
    .attr("class", "background")
    .attr("d", path);

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

svg.append("path")
    .datum(interrupt)
    .attr("class", "foreground")
    .attr("d", path);

d3.json("/d/3682676/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("/d/3682676/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);
});

</script>