// forked from bouze's hybrid-brush-03
// forked from bouze's hybrid-brush-02
// forked from bouze's hybrid-brush-01
package 
{
	import flash.display.GradientType;
	import flash.display.Graphics;
	import flash.display.Sprite;
	import flash.events.Event;
	import flash.geom.Matrix;
	import flash.geom.Point;
	
	/**
	 * ...
	 * @author bouze
	 */
	[SWF(frameRate="60", backgroundColor="#CCCC99")]
	public class Main extends Sprite
	{
		private var drawLayer:Sprite;
		private var particles:Array = new Array();
		private var pNum:int = 40;
		private var maxDistance:Number = 20;
		private var friction:Number = 0.3;
		
		public function Main()
		{
			init();
		}
		
		private function init():void
		{
			stage.quality = "LOW";
			drawLayer = new Sprite();
			addChild(drawLayer);
			initParticles();
			addEventListener(Event.ENTER_FRAME, update);
		}
		
		private function initParticles():void
		{
			var i:int;
			for (i = 0; i < pNum; i++)
			{
				
				var sp:Sprite = new Sprite();
				drawLayer.addChild( sp );
				/*
				var g:Graphics = sp.graphics;
				g.lineStyle( 1 );
				g.drawCircle( 0, 0, 4 );
				drawLayer.addChild( sp );
				*/
				
				particles.push(
				{
					ref: sp,
					x: mouseX,
					y: mouseY,
					dx: 0,
					dy: 0
				} );
			}
		}
		
		private function move():void
		{
			var i:int;
			for (i = 0; i < pNum; i++)
			{
				var p:Object = particles[ i ];
				var pp:Object = particles[ i - 1 ];
				
				if ( i == 0 )
				{
					p.x += ( mouseX - p.x ) * friction;
					p.y += ( mouseY - p.y ) * friction;
				}
				else
				{
					p.x += ( pp.x - p.x ) * friction * ( pNum - i ) * 0.08;
					p.y += ( pp.y - p.y ) * friction * ( pNum - i ) * 0.08;
				}
			}
		}
		
		private function draw():void
		{
			
			var i:int;
			for (i = 0; i < pNum - 5; i++) 
			{
				var g:Graphics = particles[ i ].ref.graphics;
				var mtrx:Matrix = new Matrix();
				mtrx =  createLinearGradientMatrix( particles[ i ].x, particles[ i ].y, particles[ i + 2 ].x, particles[ i + 2 ].y)
				g.clear();
				g.beginGradientFill(GradientType.LINEAR, [ 0x660099, 0xFF0066 ], [ 0.4, 0.3 ], [ 0, 255 ], mtrx);
				g.moveTo( particles[ i ].x, particles[ i ].y );
				
				curveThrough3Pts(g, particles[ i ].x, particles[ i ].y, particles[ i + 1 ].x, particles[ i + 1 ].y, particles[ i + 2 ].x, particles[ i + 2 ].y );
				curveThrough3Pts(g, particles[ i + 2 ].x, particles[ i + 2 ].y, particles[ i + 3 ].x, particles[ i + 3 ].y, particles[ i + 4 ].x, particles[ i + 4 ].y );
				
				/*
				g.lineTo( particles[ i + 1 ].x, particles[ i + 1 ].y );
				g.lineTo( particles[ i + 2 ].x, particles[ i + 2 ].y );
				g.lineTo( particles[ i + 3 ].x, particles[ i + 3 ].y );
				g.lineTo( particles[ i + 4 ].x, particles[ i + 4 ].y );
				g.lineTo( particles[ i + 5 ].x, particles[ i + 5 ].y );
				*/
				g.lineTo( particles[ i ].x, particles[ i ].y );
			}
			g.endFill();
		}
		
		/**
		 * 三点を通る二次元曲線
		 * via 詳説ActionScript 3.0(p.700)
		*/
		private function curveThrough3Pts
		(
			g:Graphics,
			startX:Number,
			startY:Number,
			throughX:Number,
			throughY:Number,
			endX:Number,
			endY:Number
		):void
		{
			var controlX:Number = ( 2 * throughX ) - 0.5 * ( startX + endX );
			var controlY:Number = ( 2 * throughY ) - 0.5 * ( startY + endY );
			g.moveTo( startX, startY );
			g.curveTo( controlX, controlY, endX, endY );
		}
		
		/**
		 * Make matrix for linear gradient
		 * via http://nutsu.com/blog/2009/020921_as_gradient_matrix.html
		*/
		private function createLinearGradientMatrix( x0:Number, y0:Number, x1:Number, y1:Number ):Matrix
		{
			var mtrx:Matrix = new Matrix();
			mtrx.createGradientBox( 1, 1, 0, -0.5, -0.5 );
			
			var vx:Number = x1 - x0;
			var vy:Number = y1 - y0;
			var w:Number  = Math.sqrt( vx * vx + vy * vy );
			var r:Number  = Math.atan2( vy, vx );
			var cx:Number = ( x0 + x1 ) / 2;
			var cy:Number = ( y0 + y1 ) / 2;
			
			mtrx.scale( w, 1 );
			mtrx.rotate( r );
			mtrx.translate( cx, cy );
			
			return mtrx;
		}
		
		private function update(e:Event):void
		{
			move();
			draw();
		}
	}
}

hybrid-brush-04