An update of Jason Davies’ Quadratic Koch Island Simplification stress test.
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February 9, 2016 02:00
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Snowflake Simplification
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| license: gpl-3.0 |
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| #!/usr/bin/env node | |
| var width = 960, | |
| height = 500; | |
| console.log(JSON.stringify({ | |
| type: "GeometryCollection", | |
| geometries: [ | |
| lSystem("FRFRFRFR", "FLFRFRFFLFLFRF", -Math.PI / 2, Math.PI / 2)(-128 + width * .35, height / 4), | |
| lSystem("FRFRFRFR", "FLFRFRFFLFLFRF", -Math.PI / 2, Math.PI / 2)(128 + width * .35, height / 4) | |
| ] | |
| })); | |
| function lSystem(initial, replacement, left, right) { | |
| var segments = initial.match(/F/g).length; | |
| return function(x, y) { | |
| var flake = initial, | |
| iterations = 3, | |
| d = 64 / Math.pow(segments, iterations - 1), | |
| line = []; | |
| for (var i = 0; i < iterations; ++i) flake = flake.replace(/F/g, replacement); | |
| for (var angle = 0, move, i = 0, n = flake.length; i < n; ++i) { | |
| move = flake.charAt(i); | |
| if (move === "F") { | |
| line.push([ | |
| x += d * Math.cos(angle) | 0, | |
| y += d * Math.sin(angle) | 0 | |
| ]); | |
| } else { | |
| angle += move === "L" ? left : right; | |
| } | |
| } | |
| line.push(line[0]); | |
| return {type: "Polygon", coordinates: [line]}; | |
| }; | |
| } |
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| .koch { | |
| fill: #eee; | |
| stroke: #000; | |
| } | |
| .overlay { | |
| fill: none; | |
| pointer-events: all; | |
| } | |
| </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 = 500; | |
| var area = 1, simplify = d3.geo.transform({ | |
| point: function(x, y, z) { | |
| if (z >= area) this.stream.point(x, y); | |
| } | |
| }); | |
| var x = d3.scale.sqrt() | |
| .domain([0, 1e4]) | |
| .range([0, width]); | |
| var path = d3.geo.path() | |
| .projection(simplify); | |
| var svg = d3.select("body").append("svg") | |
| .attr("width", width) | |
| .attr("height", height); | |
| svg.append("rect") | |
| .attr("class", "overlay") | |
| .attr("width", width) | |
| .attr("height", height) | |
| .on("mousemove", mousemoved); | |
| d3.json("snowflake.json", function(error, topo) { | |
| if (error) throw error; | |
| svg.insert("path", ".overlay") | |
| .datum(topojson.feature(topojson.presimplify(topo), topo.objects.snowflake)) | |
| .attr("class", "koch") | |
| .attr("d", path); | |
| }); | |
| function mousemoved() { | |
| area = x.invert(d3.mouse(this)[0]); | |
| svg.select(".koch").attr("d", path); | |
| } | |
| </script> |
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| all: snowflake.json | |
| clean: | |
| rm -f -- snowflake.json | |
| snowflake.json: create-snowflake | |
| ./create-snowflake | \ | |
| node_modules/.bin/topojson \ | |
| -o $@ \ | |
| -q 0 \ | |
| --cartesian \ | |
| -- \ | |
| snowflake=/dev/stdin |
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| { | |
| "name": "anonymous", | |
| "version": "0.0.1", | |
| "private": true, | |
| "devDependencies": { | |
| "topojson": "1" | |
| } | |
| } |
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