This example uses point-along-path interpolation, but also changes the rotation of the moving element depending on its place on the path.
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March 29, 2017 13:03
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Element rotation with point-along-path interpolation
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| #chart path.line { | |
| fill: none; | |
| stroke-width: 1; | |
| stroke: #666; | |
| stroke-dasharray: 3,3; | |
| } | |
| line { | |
| stroke: #000; | |
| stroke-width: 1; | |
| } | |
| text { | |
| font-family: Helvetica, sans-serif; | |
| font-size: 11px; | |
| text-anchor: middle; | |
| } | |
| </style> | |
| <body> | |
| <div id="chart"></div> | |
| </body> | |
| <script src="//d3js.org/d3.v3.min.js"></script> | |
| <script> | |
| var margin = {top: 20, right: 20, bottom: 20, left: 20}, | |
| width = 800 - margin.left - margin.right, | |
| height = 400 - margin.top - margin.bottom, | |
| x = d3.scale.linear() | |
| .domain([0, 20]) | |
| .range([10, width]), | |
| y = d3.scale.linear() | |
| .domain([0, 1]) | |
| .range([height, 0]), | |
| data = d3.range(x.domain()[1]).map(function(x) { | |
| return Math.random(); | |
| }), | |
| line = d3.svg.line() | |
| .interpolate("basis") | |
| .x(function(d, i) { | |
| return x(i); | |
| }) | |
| .y(y), | |
| svg = d3.select("#chart").append("svg").attr({ | |
| width: width + margin.left + margin.right, | |
| height: height + margin.top + margin.bottom | |
| }), | |
| g = svg.append("g").attr({ | |
| transform: "translate(" + margin.left + "," + margin.top + ")" | |
| }), | |
| path = g.append("path") | |
| .datum(data) | |
| .attr({ | |
| "class": "line", | |
| d: line | |
| }) | |
| pointer = g.append("g"), | |
| label = pointer.append("text") | |
| .attr({ | |
| transform: "translate(0, -10)" | |
| }) | |
| .text("Hi!"), | |
| tri = pointer.append("path") | |
| .attr({ | |
| "class": "tri", | |
| d: d3.svg.symbol().type("triangle-down").size(50)() | |
| }); | |
| var direction = -1, | |
| atLength; | |
| // From http://bl.ocks.org/mbostock/1705868 | |
| function transition() { | |
| direction *= -1; | |
| pointer.transition() | |
| .ease("linear") | |
| .duration(10000) | |
| .attrTween("transform", translateAlong(path.node())) | |
| .each("end", transition); | |
| } | |
| transition(); | |
| function translateAlong(path) { | |
| var l = path.getTotalLength(); | |
| return function(d, i, a) { | |
| return function(t) { | |
| atLength = direction === 1 ? (t * l) : (l - (t * l)); | |
| var p1 = path.getPointAtLength(atLength), | |
| p2 = path.getPointAtLength((atLength)+direction), | |
| angle = Math.atan2(p2.y - p1.y, p2.x - p1.x) * 180 / Math.PI; | |
| label.text(Math.round(angle) + "°"); | |
| return "translate(" + p1.x + "," + p1.y + ")rotate(" + angle + ")"; | |
| } | |
| } | |
| } | |
| </script> |
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