Away3D 4.1.4 中实现骨骼绑定

骨骼的绑定归根结底就是将目标骨骼的位置以及旋转数据，同步给要绑定的显示对象。

先来看BindingTag.as

package away3d.entities

{

    import away3d.arcane;

    import away3d.animators.SkeletonAnimator;

    import away3d.animators.data.JointPose;

    import away3d.containers.ObjectContainer3D;

 

    use namespace arcane

    

    public class BindingTag extends ObjectContainer3D

    {

        private var _skeletonAnimator:SkeletonAnimator;

        private var _skeletonIndex:int;

 

        /**

         *

         * @param skeletonAnimator

         * @param skeletonIndex 要绑定的骨骼索引

         *

         */    

        public function BindingTag(skeletonAnimator:SkeletonAnimator, skeletonIndex:int)

        {

            super();

            _skeletonAnimator = skeletonAnimator;

            _skeletonIndex = skeletonIndex;

        }

 

        public function notifyBindingTransformChange():void

        {

            invalidateTransform();

        }

 

        override protected function updateSceneTransform():void

        {

            if (_parent)

            {

                var jointPoses:Vector.<JointPose> = _skeletonAnimator.globalPose.jointPoses;

                if(jointPoses && jointPoses.length)

                {

                                        //取到骨骼数据并同步给当前对象

                    _sceneTransform.copyFrom( jointPoses[_skeletonIndex].toMatrix3D() );

                    _sceneTransform.append( _parent.sceneTransform );

                    _sceneTransform.prepend(transform);

                }

            }

            _sceneTransformDirty = false;

        }

 

        override public function dispose():void

        {

            //TODO:

        }

    }

}

BindingTag即是绑定在指定骨骼上的容器，假如你想绑定武器或特效，
只要将他们addChild到该BindingTag就可以了。 
下面看怎样将BindingTag集成到Away3D里面。 
为AnimatorBase添加Exit_Frame事件，至于为什么要加这个Exit_Frame事件，后面再来解释。
分别在start()以及stop()方法里添加、移除Exit_Frame事件

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if(!_broadcaster.hasEventListener(Event.EXIT_FRAME))     _broadcaster.addEventListener(Event.ENTER_FRAME, onExitFrame);   if(_broadcaster.hasEventListener(Event.EXIT_FRAME))     _broadcaster.removeEventListener(Event.EXIT_FRAME, onExitFrame);   protected function onExitFrame(event:Event):void {     //Override }

为SkeletonAnimator添加addBindingTagByName，addBindingTagByIndex方法
以及复写onExitFrame

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/**          * 绑定至通过名字指定的骨骼上          * @param boneName          * @return          *          */             public function addBindingTagByName(boneName:String):BindingTag         {             var boneIndex : int = globalPose.jointPoseIndexFromName(boneName);             if(boneIndex<0)//骨骼不存在                 return null;             return addBindingTagByIndex(boneIndex);         }           /**          * 绑定至通过骨骼索引指定的骨骼上          * @param boneIndex          * @return          *          */             public function addBindingTagByIndex(boneIndex:int):BindingTag         {             var bindingTag:BindingTag = new BindingTag(this, boneIndex);               for(var i:int = 0; i < _owners.length; i++)             {                 _owners[i].addChild(bindingTag);//将bindingTag添加至骨骼对应的Mesh             }               if(!_bindingTags)_bindingTags = new Vector.<BindingTag>();             _bindingTags.push(bindingTag);                      return bindingTag;         }           override protected function onExitFrame(event:Event):void         {             if(_bindingTags && _bindingTags.length)             {                 for (var i:int = 0; i < _bindingTags.length; i++)                 {                     _bindingTags[i].notifyBindingTransformChange();                 }             }         }

到这里就已经代码已经都修改添加完成了，下面来说下为什么要在Exit_Frame事件中通知
BindingTag更新.骨骼的更新是在skeletonAnimatior的updateGlobalProperties方法中
进行的，他的更新是在引擎执行完traverse后执行的，所以为了保证每次执行traverse时都能让
BindingTag根据骨骼更新，需在Exit_Frame时通知，否则BindingTag的更新总会延迟一帧，
从而导致跟随出现错位问题。