D3 Examples - Transition Rotation & Scale of Orthographic Projection with Easing

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<!DOCTYPE html>
<meta charset="utf-8">
<style>
​
.background {
  fill: none;
  pointer-events: all;
  stroke:grey;
}
​
.feature, {
  fill: #ccc;
  cursor: pointer;
}
​
.feature.active {
  fill: orange;
}
​
.mesh,.land {
  fill: black;
  stroke: #ddd;
  stroke-linecap: round;
  stroke-linejoin: round;
}
.water {
  fill: #00248F;
}
</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script src="//d3js.org/queue.v1.min.js"></script>
<script>
​
var width = 960,
    height = 600,
    active = d3.select(null);
​
var projection = d3.geo.orthographic()
    .scale(250)
    .translate([width / 2, height / 2])
    .clipAngle(90);
​
var path = d3.geo.path()
    .projection(projection);
​
var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height);
​
svg.append("rect")
    .attr("class", "background")
    .attr("width", width)
    .attr("height", height)
    .on("click", reset);
​
var g = svg.append("g")
    .style("stroke-width", "1.5px");
​
var countries;
var countryIDs;
​
 queue()
  .defer(d3.json, "world.json")
  .await(ready)
​
function ready(error, world) {
  if (error) throw error;
​
  countries = topojson.feature(world, world.objects.countries).features;
​
    //Adding water
    g.append("path")
      .datum({type: "Sphere"})
      .attr("class", "water")
      .attr("d", path);
​
    var world = g.selectAll("path.land")
    .data(countries)
    .enter().append("path")
    .attr("class", "land")
    .attr("d", path)
    .on("click", clicked)
​
};
​
function clicked(d) {
  if (active.node() === this) return reset();
  active.classed("active", false);
  active = d3.select(this).classed("active", true);
  
  // Clicked on feature:
  var p = d3.geo.centroid(d);
  
  // Store the current rotation and scale:
  var currentRotate = projection.rotate();
  var currentScale = projection.scale();
  
  // Calculate the future bounding box after applying a rotation:
  projection.rotate([-p[0], -p[1]]);
  path.projection(projection);
  
  // calculate the scale and translate required:
  var b = path.bounds(d);
  var nextScale = currentScale * 1 / Math.max((b[1][0] - b[0][0]) / (width/2), (b[1][1] - b[0][1]) / (height/2));
  var nextRotate = projection.rotate();
​
  // Update the map:
  d3.selectAll("path")
   .transition()
   .attrTween("d", function(d) {
      var r = d3.interpolate(currentRotate, nextRotate);
      var s = d3.interpolate(currentScale, nextScale);
        return function(t) {
          projection
            .rotate(r(Math.pow(t,0.33)))
            .scale( currentScale > nextScale ? s(Math.pow(t,0.1)) : s(Math.pow(t,3)) );
          path.projection(projection);
          return path(d);
        }
   })
   .duration(1000);
​
}
​
function reset() {
  active.classed("active", false);
  active = d3.select(null);
  
  d3.selectAll("path")
    .transition()
      .attrTween("d", function(d) {
      var s = d3.interpolate(projection.scale(), 250);
        return function(t) {
          projection
            .scale(s(t));
          path.projection(projection);
          return path(d);
        }
     })
    .duration(1000);
​
}
​
</script>
    