away3d how to move 3D object along a path - part1

away3d how to move 3D object along a path
away3d 裡有支援 path animator，可以沿著路徑移動 3D 物件，
以往必需先自己建立路徑，再丟給 PathAnimator 處理

pseudocode：
var aPath:Array = [
new Vector3D(-1000, -1000, -2000),
new Vector3D(-1000, 0, 0),
new Vector3D(1000, 0, 0),
new Vector3D(1000, 1000, -2000),
];
var p:Path = new Path(aPath);
pa = new PathAnimator(path, arrow, o);

簡單的路徑可以自己建立，但是複雜的路徑
這樣搞大概永遠都下不了班，
為了讓大家能夠準時下班，這裡介紹一個好用的工具

preFab http://www.closier.nl/prefab/
1. Geometry -> Path -> Path Editor
2. 點出你要的路徑
3. smooth or average path
4. 微調
5. Export -> Export AS3 Class -> path for Away3D

pesudocode：
var r:Array = [new Vector3D(0, 0, 0), new Vector3D(0, 0, 0), new Vector3D(0, 0, 0) ];
var o:Object = { alignToPath:true,
          targetobject:null,
          rotations:r,
          fps:30,
          offset:new Vector3D(0,100,0)
          };
// PathAWpath_0 就是匯出的 class
pa = new PathAnimator(new PathAWpath_0(), arrow, o);

這邊要注意的是 fps 記得要指定，不然不會播，
rotations 可有可無，後面 render 時再用 rotationX/Y/Z 校正會比較好處理，
preFab 也有提供 Path Animator 工具預覽效果。
完整程式碼如下：

	package
	{
	import away3d.animators.PathAnimator;
	import away3d.cameras.Camera3D;
	import away3d.containers.ObjectContainer3D;
	import away3d.containers.Scene3D;
	import away3d.containers.View3D;
	import away3d.core.utils.Debug;
	import away3d.materials.ColorMaterial;
	import away3d.materials.VideoMaterial;
	import away3d.primitives.Arrow;
	import away3d.primitives.Plane;
	import away3d.primitives.Trident;
	import com.bit101.components.PushButton;
	import flash.display.Sprite;
	import flash.display.StageAlign;
	import flash.display.StageScaleMode;
	import flash.events.Event;
	import flash.events.MouseEvent;
	import flash.geom.Vector3D;
	import myclass.data.PathAWpath_0;
	public class Main extends Sprite
	{
	private var scene:Scene3D;
	private var camera:Camera3D;
	private var view:View3D;
	private var material:VideoMaterial;
	private var container:ObjectContainer3D;
	private var lastRotationX:Number;
	private var lastRotationY:Number;
	private var move:Boolean;
	private var lastMouseY:Number;
	private var lastMouseX:Number;
	private var pa:PathAnimator;
	private var time:Number;
	private var loader:Loader3D;
	private var pb:PushButton;
	private var playAnimation:Boolean;
	private var arrow:Arrow;
	private var plane:Plane;
	public function Main():void
	{
	if (stage) init();
	else addEventListener(Event.ADDED_TO_STAGE, init);
	}
	private function init(e:Event = null):void
	{
	removeEventListener(Event.ADDED_TO_STAGE, init);
	// entry point
	stage.align = StageAlign.TOP_LEFT;
	stage.scaleMode = StageScaleMode.NO_SCALE;
	Debug.active = true;
	playAnimation = false;
	pb = new PushButton(this, 0, 0, "start", clickHandler);
	init3D();
	}
	private function clickHandler(e:MouseEvent):void
	{
	time = 0;
	var r:Array = [new Vector3D(0, 0, 0), new Vector3D(0, 0, 0), new Vector3D(0, 0, 0) ];
	var o:Object = { alignToPath:true,
	targetobject:null,
	rotations:r,
	fps:30,
	offset:new Vector3D(0,100,0)
	};
	pa = new PathAnimator(new PathAWpath_0(), arrow, o);
	playAnimation = true;
	}
	private function init3D():void
	{
	scene = new Scene3D();
	camera = new Camera3D();
	camera.y = 1000;
	camera.z = -2000;
	view = new View3D();
	view.x = stage.stageWidth / 2;
	view.y = stage.stageHeight / 2;
	view.scene = scene;
	view.camera = camera;
	addChild(view);
	var axis:Trident = new Trident(250, true);
	scene.addChild(axis);
	// 拿 flv 的材質
	material = new VideoMaterial();
	material.loop = true;
	material.file = "video/1.flv";
	material.smooth = true;
	plane = new Plane();
	plane.z = 0;
	plane.width = 1000;
	plane.height = 600;
	plane.rotationX = 90;
	plane.material = material;
	arrow = new Arrow();
	arrow.width = 200;
	arrow.height = 150;
	arrow.tailLength = 50;
	arrow.tailWidth = 125;
	arrow.thickness = 50;
	arrow.material = new ColorMaterial("random");
	container = new ObjectContainer3D(plane, arrow);
	scene.addChild(container);
	addEventListener(Event.ENTER_FRAME, _onEnterFrame);
	addEventListener(Event.ADDED_TO_STAGE, _onAddedToStage);
	}
	private function _onAddedToStage(e:Event):void
	{
	removeEventListener(Event.ADDED_TO_STAGE, _onAddedToStage);
	view.x = stage.stageWidth / 2;
	view.y = stage.stageHeight / 2;
	//stage.addEventListener(MouseEvent.MOUSE_DOWN, onMouseDown);
	//stage.addEventListener(MouseEvent.MOUSE_UP, onMouseUp);
	}
	private function onMouseUp(e:MouseEvent):void
	{
	move = false;
	}
	private function onMouseDown(e:MouseEvent):void
	{
	lastRotationX = container.rotationX;
	lastRotationY = cube.rotationY;
	lastMouseX = mouseX;
	lastMouseY = mouseY;
	move = true;
	}
	private function _onEnterFrame(e:Event):void
	{
	if (move) {
	container.rotationX = (mouseY - lastMouseY)/10 + lastRotationX;
	if (container.rotationX > 90)
	container.rotationX = 90;
	if (container.rotationX < -90)
	container.rotationX = -90;
	cube.rotationY = (lastMouseX - mouseX)/10 + lastRotationY;
	}
	if (playAnimation) {
	// play fast or slow
	time = (time +0.001 > 1)? 0 : time + 0.001;
	pa.update(time);
	// fixed arrow's rotation
	arrow.rotationX -= 180;
	camera.lookAt(arrow.position);
	}
	view.render();
	}
	}
	}

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