D3 Examples - Point-Along-Path Interpolation

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<!DOCTYPE html>
<meta charset="utf-8">
<body>
  
<style>
​
path {
  fill: none;
  stroke: #000;
  stroke-width: 3px;
}
​
circle {
  /*fill: steelblue; */
  stroke: #fff;
  stroke-width: 3px;
}
  
​
​
</style>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>
​
var points = [
  [200, 200],
  [500, 200],
  [500, 400],
  [200, 400],
  
];
  var points2 = [
  [100, 200],
  [400, 200],
  [400, 400],
  [100, 400],
  
];
​
​
var svg = d3.select("body").append("svg")
    .attr("width", 960)
    .attr("height", 500);
​
  
  
// Text to show "stopwatch"
svg.append("text").text("hey").attr("x", 700).attr("y", 50)
​
​
/////////////  RUNNER  ///////////////////////
Runner.prototype.calc_collision = function(n)
                                {
                                    var go = this.r * n;
                                    return go;
                                };
Runner.prototype.get_random_color = function()
                                {
                                    var colors = ["red", "green", "blue", "orange"]
                        random_color = Math.floor(Math.random()*colors.length);
                        return colors[random_color];
                                };
            //Runner.prototype.r = 15;
​
            function Runner(r,color,path)
            {
                this.r = r;
                this.color = color;
                this.path = path;
            }
​
  ///////////////////////////////////////////////
​
​
​
var dataset = [];
  
var path = svg.append("path")
    .data([points])
    .attr("d", d3.svg.line()
    .tension(0) // Catmull–Rom
    .interpolate("cardinal-closed"));
​
var path2 = svg.append("path")
    .data([points2])
    .attr("d", d3.svg.line()
    .tension(0) // Catmull–Rom
    .interpolate("cardinal-closed"));
  
/* 
// OPTIONAL
svg.selectAll(".point")
    .data(points)
    .enter()
    .append("circle")
    .attr("r", 4)
    .attr("transform", function(d) { return "translate(" + d + ")"; });
// OPTIONAL
  
​
var circle = svg.append("circle")
    .attr("r", 13)
    .attr("transform", "translate(" + points[0] + ")");
*/
  
  
d3.select("svg").on("click", function()
     {
        // get the mouse position coordinates
        var coordinates = [0, 0];
        //coordinates = d3.mouse(this);
        var x = coordinates[0];
        var y = coordinates[1];
                
  
            
        dataset.push(new Runner(15, "blue", 1));
​
        var circles = svg.selectAll(".circle")  //Select all circles
                          .data(dataset);
​
        circles.enter()
                .append("circle")
                .attr({cx:x, cy:y, fill: function(d){return d.get_random_color()}})
                .attr("r", function(d){return d.r})
                        .transition()
                        .duration(2000)
                .attr("transform", "translate(" + points[0] + ")")   // points[0]
                                .each("end", transition(d));
            //transition();
​
            function transition() 
            {
              circles.transition()
                  .duration(10000)
                  .attrTween("transform", translateAlong(path.node(),path2.node()))
                  .each("end", transition);
            }
​
      // Returns an attrTween for translating along the specified path element.
          function translateAlong(path1, path2) 
                {
            var length_1 = path1.getTotalLength();
            var length_2 = path2.getTotalLength();
            
            return function(d, i, a) 
            {
              return function(t) 
              {
                var p1 = path1.getPointAtLength(t * length_1);
                var p2 = path2.getPointAtLength(t * length_2);
                svg.select("text").text(Math.floor(t * 100))
                if (t < .3)
                {
                  p = p2
                }
                else
                {
                  p = p1
                  
                }
                return "translate(" + p.x + "," + p.y + ")";
              };
                    };
                    }
  
      });
​
​
​
</script>
​
    