Actionscript:
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var canvas:BitmapData = new BitmapData(400,400,false, 0x000000);
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addChild(new Bitmap(canvas));
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var pnts:Array = new Array();
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// make control points
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for (var i:int = 0; i<5; i++){
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var t:Number = i * 72 * Math.PI /180;
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pnts.push(dot(200 + 100 * Math.cos(t),200 +100 * Math.sin(t)));
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}
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addEventListener(Event.ENTER_FRAME, onLoop);
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function onLoop(evt:Event):void {
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canvas.lock();
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canvas.fillRect(canvas.rect, 0x000000);
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curve(pnts);
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canvas.unlock();
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}
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function tangent(pk1:Sprite, pk_1:Sprite){
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return new Point((pk1.x - pk_1.x) / 2, (pk1.y - pk_1.y) / 2);
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}
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// all math from http://en.wikipedia.org/wiki/Cubic_Hermite_spline
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function curve(p:Array, res:Number=.03):void{
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var px:Number = 0;
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var py:Number = 0;
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var pIter:int = p.length - 1;
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var m:Array = [];
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m[0] = tangent(p[1] , p[pIter]);
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for (var i:int = 1; i<pIter; i++){
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m[i] = tangent(p[i + 1], p[i - 1]);
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}
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m[pIter] = tangent(p[0],p[pIter-1]);
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for (var t:Number = 0; t <1; t+=res){
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var t_2:Number = t * t;
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var _1_t:Number = 1 - t;
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var _2t:Number = 2 * t;
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var h00:Number = (1 + _2t) * (_1_t) * (_1_t);
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var h10:Number = t * (_1_t) * (_1_t);
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var h01:Number = t_2 * (3 - _2t);
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var h11:Number = t_2 * (t - 1);
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for (var k:int = 0; k <pIter; k++){
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var k1:int = k + 1;
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var pk:Sprite = p[k];
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var pk1:Sprite = p[k1];
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var mk:Point = m[k];
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var mk1:Point = m[k1];
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px = h00 * pk.x + h10 * mk.x + h01 * pk1.x + h11 * mk1.x;
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py = h00 * pk.y + h10 * mk.y + h01 * pk1.y + h11 * mk1.y;
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canvas.setPixel(px, py, 0xFFFFFF);
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}
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pk = p[k];
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pk1 = p[0];
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mk = m[k];
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mk1= m[0];
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px = h00 * pk.x + h10 * mk.x + h01 * pk1.x + h11 * mk1.x;
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py = h00 * pk.y + h10 * mk.y + h01 * pk1.y + h11 * mk1.y;
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canvas.setPixel(px, py, 0xFFFFFF);
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}
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}
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// draggable dot
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function dot(xp:Number, yp:Number, col:uint = 0xFF0000, rad:Number=4):Sprite {
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var s:Sprite = Sprite(addChild(new Sprite));
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s.x = xp;
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s.y = yp;
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with(s.graphics) beginFill(col), drawCircle(0,0,rad);
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s.buttonMode = true;
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s.addEventListener(MouseEvent.MOUSE_DOWN, onDrag);
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return s;
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}
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function onDrag(evt:MouseEvent):void {
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evt.currentTarget.startDrag()
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}
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stage.addEventListener(MouseEvent.MOUSE_UP, onUp);
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function onUp(evt:MouseEvent):void{
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stopDrag();
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}
This a variation on a post from a few days ago. This shows how to create a closed Catmull Rom spline.
See the other Catmull-Rom related Posts
