Ragdoll Physics using Verlet Integration

Ragdoll Physics using Verlet Integration
based on Keith Peters's "AdvancED AS3.0 Animation"

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lines:149
license : MIT License
modified : 2010-02-02 08:49:59

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// Ragdoll Physics using Verlet Integration 
// based on Keith Peters's "AdvancED AS3.0 Animation" 
package {
	import flash.text.TextField;
	import flash.text.TextFieldAutoSize;
	import flash.ui.Keyboard;
	import flash.events.MouseEvent;
	import flash.events.KeyboardEvent;
	import flash.geom.Rectangle;
    import flash.display.Sprite;
    import flash.events.Event;
    
    public class RagDoll extends Sprite {
        private var rect_:Rectangle;
        private var pts_:Vector.<VP>;
        private var sticks_:Vector.<VS>;
        private var springs_:Vector.<VS>;
        private var kp_:Array = [
            125,150, 100,100, 150,100, 20,150, 230,150,
            80,250, 170,250, 70,350, 180,350];
        private var ks_:Array = [
            1,2,1, 1,0,1, 2,0,1, 0,3,1, 0,4,1,
            0,5,1, 5,6,1, 0,6,1, 5,7,1, 6,8,1,
            1,3,0, 1,5,0, 3,5,0,
            2,4,0, 2,6,0, 4,6,0,
            5,8,0, 6,7,0, 7,8,0,  
        ]; 
        private var k_:Number;	
        
        public function RagDoll() {
            rect_ = new Rectangle(0, 0, stage.stageWidth, stage.stageHeight);
            pts_ = new Vector.<VP>;
            for (var i:int = 0; i < kp_.length; i+=2) {
                var p:VP = new VP(kp_[i], kp_[i+1]);
                addChild(p);
                pts_.push(p)
            }
            k_ = 1 / 32; 
            sticks_ = new Vector.<VS>;
            springs_ = new Vector.<VS>;
            for (i = 0; i < ks_.length; i+=3) {
                var s:VS = new VS(pts_[ks_[i]], pts_[ks_[i+1]],
                                  ks_[i+2] ? 1 : k_);
                sticks_.push(s);
                if (!ks_[i+2]) springs_.push(s);
            }
            addEventListener(Event.ENTER_FRAME, onEnterFrame); 
            stage.addEventListener(MouseEvent.MOUSE_DOWN, onMouseDown);
            stage.addEventListener(KeyboardEvent.KEY_UP, onKeyUp);
            
            var t:TextField = new TextField();
            t.autoSize = TextFieldAutoSize.LEFT;
            t.text = "Mouse click ... Jump\n" +
 					"Up arrow key ... Tense\n" +
 					"Down arrow key ... Loose";
            addChild(t);
        }
 
        private function onEnterFrame(e:Event):void {
            for (var i:int = pts_.length - 1; i >= 0; i--) {
                var p:VP = pts_[i];
                p.y += .5; 
                p.update();
                p.constrain(rect_);
            }
            for (i = sticks_.length - 1; i >= 0; i--) {
                sticks_[i].update();
            }
            graphics.clear();        			
            for (i = sticks_.length - 1; i >= 0; i--) {
                sticks_[i].draw(graphics);
            } 
        }
        private function onMouseDown(e:MouseEvent):void {
            pts_[0].y -= 100;
        }

private function onKeyUp(e:KeyboardEvent):void {
            if (e.keyCode == Keyboard.UP && k_ <= 0.5)
                k_ *= 2;
            else if (e.keyCode == Keyboard.DOWN && k_ > 1.0/256)
                k_ /= 2;
            for (var i:int = springs_.length - 1; i >= 0; i--) {
                springs_[i].k = k_; 
            } 
        } 
    }
}

import flash.display.Graphics
import flash.geom.Rectangle;
import flash.display.Sprite;

class VP extends Sprite {
    public var x_:Number;
    public var y_:Number;
    public var px_:Number;
    public var py_:Number;
    public function VP(ax:Number, ay:Number) {
        x = px_ = ax; 
        y = py_ = ay;
        graphics.beginFill(0);
        graphics.drawCircle(0, 0, 4);
        graphics.endFill();
    }
 	public function update():void {
        var t:Number;
        t = x; x = 2 * x - px_; px_ = t;
        t = y; y = 2 * y - py_; py_ = t;
    }
    public function constrain(r:Rectangle):void {
        x = Math.max(r.left, Math.min(r.right, x));
        y = Math.max(r.top, Math.min(r.bottom, y));
    }
    override public function set x(v:Number):void {
        x_ = v;
        super.x = x_;
    }
    override public function set y(v:Number):void {
        y_ = v;
        super.y = y_;
    }
    override public function get x():Number {
        return x_;
    }
    override public function get y():Number {
        return y_;
    }  			 
}

class VS {
    private var pa_:VP;
    private var pb_:VP;
    private var len_:Number;
    private var k_:Number;
    public function VS(pa:VP, pb:VP, k:Number) {
        pa_ = pa;
        pb_ = pb; 
        len_ = Math.sqrt((pa_.x-pb_.x) * (pa_.x-pb_.x) +
		                 (pa_.y-pb_.y) * (pa_.y-pb_.y));
        k_ = k;
	}
    public function update():void {
        var dx:Number = pb_.x - pa_.x;
        var dy:Number = pb_.y - pa_.y;
        var cl:Number = Math.sqrt(dx * dx + dy * dy);
        var df:Number = len_ - cl;
        var of:Number = df * dx / cl / 2 * k_;
        pa_.x -= of; pb_.x += of;
        of = df * dy / cl / 2 * k_; 
        pa_.y -= of; pb_.y += of;   
	}
    public function draw(g:Graphics):void {
        g.lineStyle(0, 0, k_);
        g.moveTo(pa_.x, pa_.y); 
        g.lineTo(pb_.x, pb_.y);
    }
    public function set k(v:Number):void { k_ = v; }
}

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