lookTo

public function lookTo(do3d : DisplayObject3D, ray : Number3D) : void {
 
	var ease : Number = 0.1;
	var mainPosition : Number3D = new Number3D(do3d.x, do3d.y, do3d.z);
 
	var dir : Number3D = Number3D.sub(ray, mainPosition);	// 指向ray
	dir.normalize();
 
	var front : Number3D = new Number3D(do3d.transform.n13, do3d.transform.n23, do3d.transform.n33);
	front.normalize();
 
	var cross : Number3D = Number3D.cross(dir, front);
	var dot : Number = Number3D.dot(front, dir);
 
	var angle : Number = Math.acos(dot);
 
	var targetQuat : Quaternion = Quaternion.createFromAxisAngle(cross.x, cross.y, cross.z, angle * ease);
 
	do3d.transform.calculateMultiply3x3(targetQuat.matrix, do3d.transform);
}