Tributary inlet

_.md

[ Launch: Tributary inlet ] 5612014 by hemulin

config.json

{"description":"Tributary inlet","endpoint":"","display":"svg","public":true,"require":[],"fileconfigs":{"inlet.js":{"default":true,"vim":false,"emacs":false,"fontSize":12},"css.css":{"default":true,"vim":false,"emacs":false,"fontSize":12}},"fullscreen":false,"play":false,"loop":false,"restart":false,"autoinit":true,"pause":true,"loop_type":"period","bv":false,"nclones":15,"clone_opacity":0.4,"duration":3000,"ease":"linear","dt":0.01}

css.css

path {
  cursor: pointer;
  fill: #eee;
  stroke: #666;
  stroke-width: 1.5px;
}

circle {
  fill: steelblue;
  stroke: white;
  stroke-width: 1.5px;
}

inlet.js

var w = 960,
    h = 500;

var svg = d3.select("svg").append("svg:svg")
    .attr("width", w)
    .attr("height", h)
  .append("svg:g")
    .attr("transform", "translate(" + w / 2 + "," + h / 2 + ")");

var path = svg.append("svg:path")
    .attr("d", d3.svg.arc()
    .innerRadius(h / 12)
    .outerRadius(h / 6)
    .startAngle(12.55)
    .endAngle(Math.PI*2));

var circle = svg.append("svg:circle")
    .attr("r", 6.5)
    .attr("transform", "translate(0," + -h / 3 + ")");

function transition() {
  circle.transition()
      .duration(5000)
      .attrTween("transform", translateAlong(path.node()))
      .each("end", transition);
}

transition();

// Returns an attrTween for translating along the specified path element.
function translateAlong(path) {
  var l = path.getTotalLength();
  return function(d, i, a) {
    return function(t) {
      var p = path.getPointAtLength(t * l);
      return "translate(" + p.x + "," + p.y + ")";
    };
  };
}