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<html>
<head>
<title>JSXGraph example</title>
<link rel="stylesheet" type="text/css" href="../distrib/jsxgraph.css" />
<script type="text/javascript" src="/javascript/prototype/prototype.js"></script>
<script type="text/javascript" src="../distrib/jsxgraphcore.js"></script>
</head>
<body>
<h2>The Hilbert curve</h2>
<p>
The famous space filling curve drawn with JavaScript.
This web page uses the open source library <a href="http://jsxgraph.org">JSXGraph (http://jsxgraph.org)</a>.
If it is set to level=9 the curve is defined by
262 144 points - so be careful if you are using the Internet Explorer.
</p>
<div style="width:800px">
<div id="jxgbox" class="jxgbox" style="width:600px; height:600px; float:left; "></div>
<form>
<p> Max. iteration level:
<select id='maxlev' style='margin:1em'>
<option value="1"> 1
<option value="2"> 2
<option value="3"> 3
<option value="4"> 4
<option value="5"> 5
<option value="6"> 6
<option value="7"> 7
<option value="8"> 8
<option value="9"> 9
</select>
<input type="button" value=" set " onClick="doIt()" style='margin:1em'>
</p>
</form>
</div>
<br clear=all>
<div id="debug" style="display:block;"></div>
<script type="text/javascript">
/* <![CDATA[ */
var b = JXG.JSXGraph.initBoard('jxgbox', {originX: 20, originY: 20, unitX: 5, unitY: 5, zoomX:1, axis:true});
var UP = 0;
var LEFT = 1;
var DOWN = 2;
var RIGHT = 3;
var pos = [0,0];
var step = 1;
var pointsX = [0];
var pointsY = [0];
move = function(dir) {
switch (dir) {
case LEFT:
pos[0] -= step;
break;
case RIGHT:
pos[0] += step;
break;
case UP:
pos[1] += step;
break;
case DOWN:
pos[1] -= step;
break;
}
pointsX[pointsX.length] = pos[0];
pointsY[pointsY.length] = pos[1];
};
hilbert = function(level,dir) {
if (level<=1) {
switch (dir) {
case LEFT:
move(RIGHT);
move(DOWN);
move(LEFT);
break;
case RIGHT:
move(LEFT);
move(UP);
move(RIGHT);
break;
case UP:
move(DOWN);
move(RIGHT);
move(UP);
break;
case DOWN:
move(UP);
move(LEFT);
move(DOWN);
break;
}
} else {
switch (dir) {
case LEFT:
hilbert(level-1,UP);
move(RIGHT);
hilbert(level-1,LEFT);
move(DOWN);
hilbert(level-1,LEFT);
move(LEFT);
hilbert(level-1,DOWN);
break;
case RIGHT:
hilbert(level-1,DOWN);
move(LEFT);
hilbert(level-1,RIGHT);
move(UP);
hilbert(level-1,RIGHT);
move(RIGHT);
hilbert(level-1,UP);
break;
case UP:
hilbert(level-1,LEFT);
move(DOWN);
hilbert(level-1,UP);
move(RIGHT);
hilbert(level-1,UP);
move(UP);
hilbert(level-1,RIGHT);
break;
case DOWN:
hilbert(level-1,RIGHT);
move(UP);
hilbert(level-1,DOWN);
move(LEFT);
hilbert(level-1,DOWN);
move(DOWN);
hilbert(level-1,LEFT);
break;
}
}
};
var s = b.createElement('slider', [[0,-110],[50,-110],[1,2,7]], {name:'S',snapWidth:1});
var curve = b.createElement('curve',[pointsX,pointsY],{curveType:'plot'});
function doIt(){
pos = [0,0];
pointsX = [0];
pointsY = [0];
maxlev = $('maxlev').value;
step = 50/(Math.pow(2,maxlev-1));
hilbert(maxlev,LEFT);
curve.dataX = pointsX;
curve.dataY = pointsY;
b.update();
}
var oldlev = -1;
curve.updateDataArray = function() {
maxlev = s.Value();
if (oldlev==maxlev) {
return;
}
pos = [0,0];
pointsX = [0];
pointsY = [0];
step = 50/(Math.pow(2,maxlev-1));
hilbert(maxlev,LEFT);
this.dataX = pointsX;
this.dataY = pointsY;
oldlev=maxlev;
};
/* ]]> */
</script>
</body>
</html>
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