很多简单的互动不需要精确到建模射线检测, 直接使用全局触控即可
[code] var _self = this;
document.addEventListener("mousedown",function(event){_self.onActDown(event);},false);
document.addEventListener("mouseup",function(event){_self.onActUp(event);},false);
document.addEventListener( 'touchstart', function(event){ _self.onActDown(event) }, false );
document.addEventListener( 'touchend', function(event){ _self.onActUp(event) }, false );
document.addEventListener( 'touchcancel', function(event){ _self.onActUp(event) }, false );[/code]
