flash on 2011-3-1

/**
 * Copyright yama3 ( http://wonderfl.net/user/yama3 )
 * MIT License ( http://www.opensource.org/licenses/mit-license.php )
 * Downloaded from: http://wonderfl.net/c/fTXg
 */

package {
    import flash.text.*;
    import flash.filters.*;
    import flash.geom.*;
    import flash.events.*;
    import flash.display.*;
    [SWF(frameRate = 60)];
    
    public class FlashTest extends Sprite {
        public static const GRAVITY:Number = 0.05;
        public static const RANGE:Number = 12;
        public static const RANGE2:Number = RANGE * RANGE;
        public static const DENSITY:Number = 1;
        public static const PRESSURE:Number = 2;
        public static const VISCOSITY:Number = 0.075;
        private var img:BitmapData;
        private var particles:Vector.<Particle>;
        private var numParticles:uint;
        private var color:ColorTransform;
        private var filter:BlurFilter;
        private var count:int;
        private var press:Boolean;
        
        public function FlashTest() {
            initialize();            
        }
        
        private function initialize():void {
            color = new ColorTransform(0.5, 0.9, 0.95);
            filter = new BlurFilter(2, 2, 1);
            particles = new Vector.<Particle>();
            numParticles = 0;
            count = 0;
            img = new BitmapData(465, 465, false, 0);
            addChild(new Bitmap(img));
            addEventListener(Event.ENTER_FRAME, frame);
            stage.addEventListener(MouseEvent.MOUSE_DOWN, function(e:MouseEvent):void{press = true;});
            stage.addEventListener(MouseEvent.MOUSE_UP, function(e:MouseEvent):void {press = false;});
        }
        
        private function frame(e:Event):void {
            if(press)
            pour();
            move();
            img.lock();
            img.colorTransform(img.rect, color);
            img.applyFilter(img, img.rect, new Point(), filter);
            draw();
            img.unlock();
        }
        
        private function draw():void {
            for(var i:int=0; i<numParticles; i++) {
                var p:Particle = particles[i];
                img.fillRect(new Rectangle(p.x - 1, p.y - 1, 2, 2), p.color);
            }
        }
        
        private function pour():void {
            for(var i:int = -3; i <= 3; i++) {
                particles[numParticles++] = new Particle(mouseX + i * 8, 5);
                particles[numParticles - 1].vy = 5;
            }
        }
        
        private function move():void {
            count++;
            var i:int;
            var j:int;
            var dist:Number;
            var pi:Particle;
            var pj:Particle;
            var dx:Number;
            var dy:Number;
            var weight:Number;
            var pressureWeight:Number;
            var viscosityWeight:Number;
            for(i = 0; i < numParticles; i++) {
                pi = particles[i];
                pi.numNeighbors = 0;
                for(j=0; j<i; j++) {
                    pj = particles[j];
                    if((pi.x - pj.x) * (pi.x - pj.x) + (pi.y - pj.y) * (pi.y - pj.y) < RANGE2) {
                        pi.neighbors[pi.numNeighbors++] = pj;
                        pj.neighbors[pj.numNeighbors++] = pi;
                    }
                }
            }
            for(i = 0; i < numParticles; i++) {
                pi = particles[i];
                pi.density = 0;
                for(j = 0; j < pi.numNeighbors; j++) {
                    pj = pi.neighbors[j];
                    dist = Math.sqrt((pi.x - pj.x) * (pi.x - pj.x) + (pi.y - pj.y) * (pi.y - pj.y));
                    pi.density += (1 - dist / RANGE) * (1 - dist / RANGE);
                }
                if(pi.density < DENSITY)
                pi.density = DENSITY;
                pi.pressure = pi.density - DENSITY;
            }
            for(i = 0; i < numParticles; i++) {
                pi = particles[i];
                pi.fx = 0;
                pi.fy = 0;
                for(j = 0; j < pi.numNeighbors; j++) {
                    pj = pi.neighbors[j];
                    dx = pi.x - pj.x;
                    dy = pi.y - pj.y;
                    dist = Math.sqrt(dx * dx + dy * dy);
                    weight = 1 - dist / RANGE;
                    pressureWeight = weight * (pi.pressure + pj.pressure)/(2*pj.density)*PRESSURE;
                    dist = 1 / dist;
                    dx *= dist;
                    dy *= dist;
                    pi.fx += dx * pressureWeight;
                    pi.fy += dy * pressureWeight;
                    viscosityWeight = weight / pj.density * VISCOSITY;
                    dx = pi.vx - pj.vx;
                    dy = pi.vy - pj.vy;
                    pi.fx -= dx * viscosityWeight;
                    pi.fy -= dy * viscosityWeight;
                }
            }
            for(i = 0; i < numParticles; i++) {
                pi = particles[i];
                pi.move();
            }
        }
    }
}

class Particle {
    public var x:Number;
    public var y:Number;
    public var vx:Number;
    public var vy:Number;
    public var fx:Number;
    public var fy:Number;
    public var density:Number;
    public var pressure:Number;
    public var neighbors:Vector.<Particle>;
    public var numNeighbors:int;
    public var color:int;
    public function Particle(x:Number, y:Number) {
        this.x = x;
        this.y = y;
        vx = vy = fx = fy = 0;
        neighbors = new Vector.<Particle>();
        color = 0xffffff;
    }
    
    public function move():void {
        vy += FlashTest.GRAVITY;
        vx += fx;
        vy += fy;
        x += vx;
        y += vy;
        if(x < 5)
        vx += 5 - x;
        if(y < 5)
        vy += 5 - y;
        if(x > 460)
        vx += 460 - x;
        if(y > 460)
        vy += 460 - y;
    }    
}