A rotating Cassini projection (transverse equirectangular) on the left; a rotating transverse Mercator projection on the right.
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November 7, 2016 21:23
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Rotating Transverse
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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 src="//d3js.org/topojson.v1.min.js"></script> | |
| <script> | |
| var width = 960, | |
| height = 580, | |
| velocity = .003, | |
| time = Date.now(); | |
| var position = d3.scale.ordinal() | |
| .domain([0, 1]) | |
| .rangePoints([0, width * .87], .8); | |
| var projections = [ | |
| d3.geo.equirectangular() | |
| .scale(85) | |
| .translate([position(0), height / 2]) | |
| .precision(.3), | |
| d3.geo.mercator() | |
| .scale(85) | |
| .translate([position(1), height / 2]) | |
| .precision(.3) | |
| ]; | |
| var sphere = {type: "Sphere"}, | |
| graticule = d3.geo.graticule()(); | |
| var canvas = d3.select("body").append("canvas") | |
| .attr("width", width) | |
| .attr("height", height); | |
| var context = canvas.node().getContext("2d"); | |
| context.strokeStyle = "#aaa"; | |
| var path = d3.geo.path() | |
| .context(context); | |
| d3.json("/mbostock/raw/4090846/world-110m.json", function(error, world) { | |
| if (error) throw error; | |
| var land = topojson.feature(world, world.objects.land); | |
| d3.timer(function() { | |
| var dt = Date.now() - time; | |
| projections[0].rotate([velocity * dt, 0, 90]); | |
| projections[1].rotate([velocity * dt, 0, 90]); | |
| render(); | |
| }); | |
| function render() { | |
| context.clearRect(0, 0, width, height); | |
| projections.forEach(function(projection) { | |
| var translate = projection.translate(); | |
| context.save(); | |
| context.translate(translate[0], translate[1]); | |
| context.rotate(Math.PI / 2); | |
| context.translate(-translate[0], -translate[1]); | |
| path.projection(projection); | |
| context.beginPath(); | |
| path(sphere); | |
| context.stroke(); | |
| context.beginPath(); | |
| path(graticule); | |
| context.stroke(); | |
| context.beginPath(); | |
| path(land); | |
| context.fill(); | |
| context.restore(); | |
| }); | |
| } | |
| }); | |
| d3.select(self.frameElement).style("height", height + "px"); | |
| </script> |
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