Add an example that renders a simple fractal
This works at resolutions where simplification is significantly reducing the number of points in the line. At high resolutions, navigation becomes unresponsive. Limiting draw instructions to a replay group's extent will fix this.
This commit is contained in:
Tim Schaub
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examples/fractal.html
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examples/fractal.html
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<!doctype html>
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<html lang="en">
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<head>
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<meta charset="utf-8">
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<meta http-equiv="X-UA-Compatible" content="chrome=1">
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<meta name="viewport" content="initial-scale=1.0, user-scalable=no, width=device-width">
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<link rel="stylesheet" href="../css/ol.css" type="text/css">
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<link rel="stylesheet" href="../resources/bootstrap/css/bootstrap.min.css" type="text/css">
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<link rel="stylesheet" href="../resources/layout.css" type="text/css">
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<link rel="stylesheet" href="../resources/bootstrap/css/bootstrap-responsive.min.css" type="text/css">
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<title>Fractal Example</title>
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<style>
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.map {
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background: whitesmoke;
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}
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#depth {
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width: 100px;
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}
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</style>
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</head>
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<body>
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<div class="navbar navbar-inverse navbar-fixed-top">
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<div class="navbar-inner">
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<div class="container">
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<a class="brand" href="./"><img src="../resources/logo.png"> OpenLayers 3 Examples</a>
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</div>
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</div>
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</div>
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<div class="container-fluid">
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<div class="row-fluid">
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<div class="span12">
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<div id="map" class="map"></div>
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</div>
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</div>
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<div class="row-fluid">
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<div class="span12">
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<h4 id="title">Fractal Example</h4>
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<p id="shortdesc">Example of a fractal.</p>
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<label for="depth">
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depth:
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<input id="depth" type="range" min="0" max="9" step="1" value="5">
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(<span id="count">#</span> points)
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</label>
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<div id="docs">
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<p>See the <a href="fractal.js" target="_blank">fractal.js source</a> to see how this is done.</p>
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</div>
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<div id="tags">fractal, vector</div>
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</div>
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</div>
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</div>
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<script src="jquery.min.js" type="text/javascript"></script>
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<script src="../resources/example-behaviour.js" type="text/javascript"></script>
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<script src="loader.js?id=fractal" type="text/javascript"></script>
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</body>
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</html>
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125
examples/fractal.js
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examples/fractal.js
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goog.require('ol.Feature');
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goog.require('ol.Map');
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goog.require('ol.View2D');
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goog.require('ol.geom.LineString');
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goog.require('ol.layer.Vector');
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goog.require('ol.source.Vector');
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var radius = 10e6;
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var cos30 = Math.cos(Math.PI / 6);
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var sin30 = Math.sin(Math.PI / 6);
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var rise = radius * sin30;
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var run = radius * cos30;
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var triangle = new ol.geom.LineString([
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[0, radius], [run, -rise], [-run, -rise], [0, radius]
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]);
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var feature = new ol.Feature(triangle);
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var layer = new ol.layer.Vector({
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source: new ol.source.Vector({
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features: [feature]
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})
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});
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var map = new ol.Map({
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layers: [layer],
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renderer: 'canvas',
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target: 'map',
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view: new ol.View2D({
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center: [0, 0],
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zoom: 1
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})
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});
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function makeFractal(depth) {
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var geometry = /** @type {ol.geom.LineString} */ (triangle.clone());
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var graph = coordsToGraph(geometry.getCoordinates());
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for (var i = 0; i < depth; ++i) {
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var node = graph;
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while (node.next) {
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var next = node.next;
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injectNodes(node);
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node = next;
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}
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}
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var coordinates = graphToCoords(graph);
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document.getElementById('count').innerHTML = coordinates.length;
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geometry.setCoordinates(coordinates);
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feature.setGeometry(geometry);
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}
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function injectNodes(startNode) {
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var endNode = startNode.next;
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var start = startNode.point;
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var end = startNode.next.point;
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var dx = end[0] - start[0];
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var dy = end[1] - start[1];
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// first point at 1/3 along the segment
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var firstNode = {
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point: [start[0] + dx / 3, start[1] + dy / 3]
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};
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// second point at peak of _/\_
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var r = Math.sqrt(dx * dx + dy * dy) / (2 * cos30);
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var a = Math.atan2(dy, dx) + Math.PI / 6;
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var secondNode = {
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point: [start[0] + r * Math.cos(a), start[1] + r * Math.sin(a)]
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};
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// third point at 2/3 along the segment
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var thirdNode = {
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point: [end[0] - dx / 3, end[1] - dy / 3]
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};
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startNode.next = firstNode;
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firstNode.next = secondNode;
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secondNode.next = thirdNode;
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thirdNode.next = endNode;
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}
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function coordsToGraph(coordinates) {
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var graph = {
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point: coordinates[0]
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};
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var length = coordinates.length;
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for (var level = 0, node = graph; level < length - 1; ++level) {
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node.next = {
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point: coordinates[level + 1]
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};
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node = node.next;
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}
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return graph;
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}
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function graphToCoords(graph) {
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var coordinates = [graph.point];
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for (var node = graph, i = 1; node.next; node = node.next, ++i) {
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coordinates[i] = node.next.point;
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}
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return coordinates;
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}
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var depthInput = document.getElementById('depth');
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function update() {
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makeFractal(Number(depthInput.value));
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}
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var updateTimer;
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/**
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* Regenerate fractal on depth change. Change events are debounced so updates
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* only occur every 200ms.
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*/
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depthInput.onchange = function() {
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window.clearTimeout(updateTimer);
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updateTimer = window.setTimeout(update, 200);
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};
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update();
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