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rhill-voronoi-demo4.html
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<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<title>Javascript implementation of Steven Fortune's algorithm to compute Voronoi diagrams: Demo 4</title>
<meta name="Keywords" lang="en" content="voronoi, fortune, javascript, raymond hill"/>
<!--[if lte IE 8]><script type="text/javascript" src="excanvas/excanvas.compiled.js"></script><![endif]-->
<script type="text/javascript" src="rhill-voronoi-core.min.js"></script>
<script type="text/javascript" src="QuadTree.js"></script>
<style type="text/css">
body {font-family:tahoma,verdana,arial;font-size:13px;margin:0;padding:0}
body > div {margin-left:4px;margin-right:4px;}
body > div > div {margin:0;border:1px solid #ccc;border-top:0;padding:4px;}
h1 {margin:0 0 0.5em 0;padding: 4px 5em 4px 4px;font:bold large sans-serif;background-color:#c9d7f1;}
h4 {font-size:14px;margin:0.5em 0 0 0;border:0;border-bottom:solid 1px #c9d7f1;padding:2px;background-color:#e5ecf9;}
#canvasParent {margin-top:0;margin-bottom:1em;padding:0;border:0}
#voronoiCode {font:11px monospace;overflow:auto;color:#666;}
#voronoiCode span {color:green;font-weight:bold;}
</style>
<script id="script" type="text/javascript">
var VoronoiDemo = {
voronoi: new Voronoi(),
sites: [],
diagram: null,
margin: 0.1,
canvas: null,
bbox: {xl:0,xr:800,yt:0,yb:600},
lastCell: undefined,
treemap: null,
init: function() {
this.canvas = document.getElementById('voronoiCanvas');
this.randomSites(100,true);
this.render();
},
clearSites: function() {
this.sites = [];
this.treemap = null;
this.diagram = this.voronoi.compute(this.sites, this.bbox);
this.updateStats();
},
randomSites: function(n,clear) {
if (clear) {this.sites = [];}
// create vertices
var xmargin = this.canvas.width*this.margin,
ymargin = this.canvas.height*this.margin,
xo = xmargin,
dx = this.canvas.width-xmargin*2,
yo = ymargin,
dy = this.canvas.height-ymargin*2;
for (var i=0; i<n; i++) {
this.sites.push({x:self.Math.round((xo+self.Math.random()*dx)*10)/10,y:self.Math.round((yo+self.Math.random()*dy)*10)/10});
}
this.treemap = null;
this.diagram = this.voronoi.compute(this.sites, this.bbox);
this.updateStats();
},
recompute: function() {
this.treemap = null;
this.diagram = this.voronoi.compute(this.sites, this.bbox);
this.updateStats();
},
updateStats: function() {
if (!this.diagram) {return;}
var e = document.getElementById('voronoiStats');
if (!e) {return;}
e.innerHTML = '('+this.diagram.cells.length+' Voronoi cells computed from '+this.diagram.cells.length+' Voronoi sites in '+this.diagram.execTime+' ms – rendering <i>not</i> included)';
},
buildTreemap: function() {
var treemap = new QuadTree({
x: this.bbox.xl,
y: this.bbox.yt,
width: this.bbox.xr-this.bbox.xl,
height: this.bbox.yb-this.bbox.yt
});
var cells = this.diagram.cells,
iCell = cells.length;
while (iCell--) {
bbox = cells[iCell].getBbox();
bbox.cellid = iCell;
treemap.insert(bbox);
}
return treemap;
},
cellUnderMouse: function(ev) {
if (!this.diagram) {return;}
var canvas = document.getElementById('voronoiCanvas');
if (!canvas) {
return;
}
// >>> http://www.quirksmode.org/js/events_properties.html#position
var x = 0,
y = 0;
if (!ev) {
ev = window.event;
}
if (ev.pageX || ev.pageY) {
x = ev.pageX;
y = ev.pageY;
}
else if (e.clientX || e.clientY) {
x = ev.clientX + document.body.scrollLeft + document.documentElement.scrollLeft;
y = ev.clientY + document.body.scrollTop + document.documentElement.scrollTop;
}
// <<< http://www.quirksmode.org/js/events_properties.html#position
x -= canvas.offsetLeft;
y -= canvas.offsetTop;
cellid = this.cellIdFromPoint(x,y);
if (this.lastCell !== cellid) {
if (this.lastCell !== undefined) {
this.renderCell(this.lastCell, '#fff', '#000');
}
if (cellid !== undefined) {
this.renderCell(cellid, '#f00', '#00f');
}
this.lastCell = cellid;
}
document.getElementById('voronoiCellid').innerHTML = "(" + x + "," + y + ") = " + cellid;
},
cellIdFromPoint: function(x, y) {
// We build the treemap on-demand
if (this.treemap === null) {
this.treemap = this.buildTreemap();
}
// Get the Voronoi cells from the tree map given x,y
var items = this.treemap.retrieve({x:x,y:y}),
iItem = items.length,
cells = this.diagram.cells,
cell, cellid;
while (iItem--) {
cellid = items[iItem].cellid;
cell = cells[cellid];
if (cell.pointIntersection(x,y) > 0) {
return cellid;
}
}
return undefined;
},
renderCell: function(id, fillStyle, strokeStyle) {
if (id === undefined) {return;}
if (!this.diagram) {return;}
var cell = this.diagram.cells[id];
if (!cell) {return;}
var ctx = this.canvas.getContext('2d');
ctx.globalAlpha = 1;
// edges
ctx.beginPath();
var halfedges = cell.halfedges,
nHalfedges = halfedges.length,
v = halfedges[0].getStartpoint();
ctx.moveTo(v.x,v.y);
for (var iHalfedge=0; iHalfedge<nHalfedges; iHalfedge++) {
v = halfedges[iHalfedge].getEndpoint();
ctx.lineTo(v.x,v.y);
}
ctx.fillStyle = fillStyle;
ctx.strokeStyle = strokeStyle;
ctx.fill();
ctx.stroke();
// site
v = cell.site;
ctx.fillStyle = '#44f';
ctx.beginPath();
ctx.rect(v.x-2/3,v.y-2/3,2,2);
ctx.fill();
},
render: function() {
var ctx = this.canvas.getContext('2d');
// background
ctx.globalAlpha = 1;
ctx.beginPath();
ctx.rect(0,0,this.canvas.width,this.canvas.height);
ctx.fillStyle = 'white';
ctx.fill();
ctx.strokeStyle = '#888';
ctx.stroke();
// voronoi
if (!this.diagram) {return;}
// edges
ctx.beginPath();
ctx.strokeStyle = '#000';
var edges = this.diagram.edges,
iEdge = edges.length,
edge, v;
while (iEdge--) {
edge = edges[iEdge];
v = edge.va;
ctx.moveTo(v.x,v.y);
v = edge.vb;
ctx.lineTo(v.x,v.y);
}
ctx.stroke();
// sites
ctx.beginPath();
ctx.fillStyle = '#44f';
var sites = this.sites,
iSite = sites.length;
while (iSite--) {
v = sites[iSite];
ctx.rect(v.x-2/3,v.y-2/3,2,2);
}
ctx.fill();
},
};
</script>
</head>
<body onload="VoronoiDemo.init();">
<a href="https://github.com/gorhill/Javascript-Voronoi"><img style="position: absolute; top: 0; right: 0; border: 0;" src="https://s3.amazonaws.com/github/ribbons/forkme_right_red_aa0000.png" alt="Fork me on GitHub"></a>
<h1>Javascript implementation of Steven Fortune's algorithm to compute Voronoi diagrams<br/>Demo 4: Looking up a Voronoi cell using a quadtree</h1>
<div id="divroot" style="width:800px;">
<p style="margin-top:0;margin-bottom:0"><a href="/voronoi/rhill-voronoi.html">< Back to main page</a><ul style="margin-top:0">
<li><a href="rhill-voronoi-demo1.html">Demo 1: measuring peformance</a>
<li><a href="rhill-voronoi-demo2.html">Demo 2: a bit of interactivity</a>
<li><a href="rhill-voronoi-demo3.php">Demo 3: Fancy tiling</a>
<li><b>Demo 4: Looking up a Voronoi cell using a quadtree</b>
<li><a href="rhill-voronoi-demo5.html">Demo 5: Lloyd's relaxation</a>
<li><a href="http://www.raymondhill.net/blog/?p=458#comments">Comments</a>
</ul></p>
<h4 class="divhdr">Sites generator</h4>
<div class="divinfo" id="voronoiGenerator">
<input type="button" value="Generate" onclick="VoronoiDemo.randomSites(parseInt(document.getElementById('voronoiNumberSites').value,10),true);VoronoiDemo.render();"/> or <input type="button" value="Add" onclick="VoronoiDemo.randomSites(parseInt(document.getElementById('voronoiNumberSites').value,10),false);VoronoiDemo.render();"/><input id="voronoiNumberSites" type="text" value="100" size="5" maxlength="5"/> sites randomly (Warning: performance might suffer the more sites you add.)
<br/><input id="voronoiClearSites" type="button" value="Clear all sites" onclick="VoronoiDemo.clearSites();VoronoiDemo.render();"/>
</div>
<h4 class="divhdr">Canvas <span id="voronoiStats" style="font:normal 11px sans"></span> <span style="font:normal 11px sans"> / Cell id at <span id="voronoiCellid" style="font:normal 11px sans"></span></span></h4>
<div id="canvasParent">
<noscript>You need to enable Javascript in your browser for this page to display properly.</noscript>
<canvas id="voronoiCanvas" width="800" height="600" onclick="VoronoiDemo.recompute();" onmousemove="VoronoiDemo.cellUnderMouse(event);"></canvas>
<div id="voronoiNoCanvasAlert" style="display:none;padding:1em;background-color:#fcc;color:black;">
<p>Your browser doesn't support the HTML5 <canvas> element technology.</p>
<p>See <a target="_blank" href="http://en.wikipedia.org/wiki/Canvas_(HTML_element)">Wikipedia</a> for information on which browsers support the <u>HTML5 <canvas></u> technology.</p>
</div>
</div>
<h4 class="divhdr">Javascript source code for this page</h4>
<div class="divinfo" id="voronoiCode">
<pre>
<span><script type="text/javascript" src="<a href="rhill-voronoi-core.js" target="_blank">rhill-voronoi-core.js</a>"></script></span>
<span><script type="text/javascript" src="<a href="https://github.com/mikechambers/ExamplesByMesh/blob/master/JavaScript/QuadTree/src/QuadTree.js" target="_blank">QuadTree.js</a>"></script></span>
...
<div id="scriptContainer"></div>
...
</pre>
</div>
</div>
<script>
(function(){
var srcElem = document.getElementById("script");
if (srcElem) {
var dstElem = document.getElementById("scriptContainer");
if (dstElem) {
dstElem.innerText = srcElem.innerHTML;
}
}
})();
</script>
</body>
</html>