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Scale-Dependent Sampling
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| license: gpl-3.0 |
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <body> | |
| <script src="//d3js.org/d3.v3.min.js"></script> | |
| <script> | |
| var width = 960, | |
| height = 500, | |
| graticulePrecision = 1; | |
| var buffer, bufferContext = { | |
| moveTo: function(x, y) { buffer.push([x, y]); }, | |
| lineTo: function(x, y) { buffer.push([x, y]); }, | |
| closePath: function() {} | |
| }; | |
| var projection = d3.geo.equirectangular() | |
| .rotate([0, 0, 89]) | |
| .translate([width / 2, height / 2]) | |
| .scale(145) | |
| .precision(.3) | |
| .clipExtent([[-1, -1], [width + 1, height + 1]]); | |
| var canvas = d3.select("body").append("canvas") | |
| .attr("width", width) | |
| .attr("height", height); | |
| var context = canvas.node().getContext("2d"), | |
| path = d3.geo.path().projection(projection).context(context), | |
| graticule = d3.geo.graticule()(), | |
| sphere = {type: "Sphere"}, | |
| equator = {type: "LineString", coordinates: [[-180, 0], [-90, 0], [0, 0], [90, 0], [180, 0]]}; | |
| animation(); | |
| function animation() { | |
| canvas.transition() | |
| .duration(7500) | |
| .tween("projection", function() { | |
| var scale = d3.interpolate(145, 145 * 32), | |
| translate = d3.interpolate([width / 2, height / 2], [1076, -6457]); | |
| return function(t) { | |
| projection.scale(scale(t)).translate(translate(t)); | |
| render(); | |
| }; | |
| }) | |
| .transition() | |
| .duration(7500) | |
| .tween("projection", function() { | |
| var scale = d3.interpolate(145 * 32, 145), | |
| translate = d3.interpolate([1076, -6457], [width / 2, height / 2]); | |
| return function(t) { | |
| projection.scale(scale(t)).translate(translate(t)); | |
| render(); | |
| }; | |
| }) | |
| .transition() | |
| .duration(2500) | |
| .each("end", animation); | |
| } | |
| function render() { | |
| context.clearRect(0, 0, width, height); | |
| if (d3.event) projection | |
| .translate(d3.event.translate) | |
| .scale(d3.event.scale); | |
| context.strokeStyle = "#aaa"; | |
| context.lineWidth = 1; | |
| context.beginPath(); | |
| path(graticule); | |
| context.stroke(); | |
| context.lineWidth = 2; | |
| context.beginPath(); | |
| path(sphere); | |
| context.stroke(); | |
| context.strokeStyle = "red"; | |
| context.beginPath(); | |
| path(equator); | |
| context.stroke(); | |
| // Override the path context to extract the resampled points. | |
| buffer = []; | |
| path.context(bufferContext); | |
| path(equator); | |
| buffer.forEach(function(d) { | |
| context.beginPath(); | |
| context.arc(d[0], d[1], 4.5, 0, 2 * Math.PI, false); | |
| context.stroke(); | |
| }); | |
| path.context(context); | |
| context.restore(); | |
| } | |
| </script> |
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