xna相机沿2个轴跟随对象？

        Matrix rotationMatrix = Matrix.CreateRotationY(avatarYaw);
        Matrix rotationMatrix2 = Matrix.CreateRotationX(avatarXaw);

        Vector3 transformedheadOffset2;
        Vector3 transformedReference2;

            transformedheadOffset2 = Vector3.Transform(AvatarHeadOffset, rotationMatrix);
            transformedReference2 = Vector3.Transform(TargetOffset, rotationMatrix);