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Last active February 26, 2019 22:34
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Floating Landmasses
license: gpl-3.0
redirect: https://observablehq.com/@mbostock/floating-landmasses

By changing the scale and clip angle of an orthographic projection, this example creates two concentric spheres to give the appearance of floating landmasses. Inspired by Derek Watkin’s Faux-3D Arcs.

<!DOCTYPE html>
<meta charset="utf-8">
<style>
body {
background: #fcfcfa;
}
canvas {
position: absolute;
top: 0;
left: 0;
}
.blur {
-webkit-filter: blur(6px);
filter: blur(6px);
}
</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>
var width = 960,
height = 960,
speed = -1e-2,
start = Date.now();
var sphere = {type: "Sphere"};
var projection = d3.geo.orthographic()
.translate([width / 2, height / 2])
.precision(.5);
var graticule = d3.geo.graticule();
var canvas1 = d3.select("body").append("canvas"),
canvas2 = d3.select("body").append("canvas").attr("class", "blur"),
canvas3 = d3.select("body").append("canvas");
d3.selectAll("canvas")
.attr("width", width)
.attr("height", height);
var context1 = canvas1.node().getContext("2d"),
context2 = canvas2.node().getContext("2d"),
context3 = canvas3.node().getContext("2d");
var path = d3.geo.path()
.projection(projection);
projection.scale(width / 2.3).clipAngle(90);
context1.beginPath();
path.context(context1)(sphere);
context1.lineWidth = 3;
context1.strokeStyle = "#000";
context1.stroke();
context1.beginPath();
path(sphere);
context1.fillStyle = "#fff";
context1.fill();
context2.fillStyle = "rgba(0,0,0,.4)";
context3.strokeStyle = "rgba(0,0,0,.2)";
d3.json("/mbostock/raw/4090846/world-110m.json", function(error, topo) {
if (error) throw error;
var land = topojson.feature(topo, topo.objects.land),
grid = graticule();
d3.timer(function() {
context2.clearRect(0, 0, width, height);
context3.clearRect(0, 0, width, height);
projection.rotate([speed * (Date.now() - start), -15]);
projection.scale(width / 2.3).clipAngle(90);
context2.beginPath();
path.context(context2)(land);
context2.fill();
context3.beginPath();
path.context(context3)(grid);
context3.lineWidth = .5;
context3.stroke();
projection.scale(width / 2.2).clipAngle(106.3);
context3.beginPath();
path(land);
context3.fillStyle = "#737368";
context3.fill();
projection.scale(width / 2.2).clipAngle(90);
context3.beginPath();
path(land);
context3.fillStyle = "#dadac4";
context3.fill();
});
});
d3.select(self.frameElement).style("height", height + "px");
</script>
@durk1234
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Hmmm... is it rotating in the correct direction? ;-)

Awesome viz, btw.

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