如何让3D物体在xy平面上做曲线运动时其z轴旋转角度也跟着变化？

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[code] //计算与上一次X坐标的差值

            let speedX = newPos.x - pathItem.item.transform.position.x;
            //计算与上一次Y坐标的差值
            let speedY = newPos.y - pathItem.item.transform.position.y;
            let angle = 0;
            //得到差值向量的弧度
            angle = Math.atan2(speedY , speedX);
            //计算与上一次弧度的差值
            let dis = angle - pathItem.angle
            pathItem.angle = angle;
            //物体旋转
            pathItem.item.transform.rotate(new Laya.Vector3(0,0,dis), false, true);
            //物体平移
            pathItem.item.transform.position = new Laya.Vector3(newPos.x, newPos.y, pathItem.item.transform.position.z);[/code]