关于拖动旋转的一些疑问

Question

在网上看到一个鼠标拖动旋转的功能实现

public void OnBeginDrag(PointerEventData data)
        {
            if (!isActive)
            {
                return;
            }

            isSpinning = true;

            playerController.StopMoving();

            // get the angle to the mouse position on down frame
            Vector3 inputPosition = new Vector3(data.position.x, data.position.y, 0f);
            directionToMouse = inputPosition - Camera.main.WorldToScreenPoint(pivot.position);

            // store the angle to mouse pointer on down frame
            previousAngleToMouse = Mathf.Atan2(directionToMouse.y, directionToMouse.x) * Mathf.Rad2Deg;

        }

public void OnDrag(PointerEventData data)
        {
            if (isSpinning && Camera.main != null && pivot != null && isActive)
            {
                // get the angle to the current mouse position
                Vector3 inputPosition = new Vector3(data.position.x, data.position.y, 0f);
                directionToMouse = inputPosition - Camera.main.WorldToScreenPoint(pivot.position);
                angleToMouse = Mathf.Atan2(directionToMouse.y, directionToMouse.x) * Mathf.Rad2Deg;

                // if we have dragged a minimum threshold, rotate the target to follow the mouse movements around the pivot
                // (left-handed coordinate system; positive rotations are clockwise)
                if (directionToMouse.magnitude > minDragDist)
                {
                    Vector3 newRotationVector = (previousAngleToMouse - angleToMouse) * axisDirection;
                    targetToSpin.Rotate(newRotationVector);
                    previousAngleToMouse = angleToMouse;
                }
            }
        }

代码是在拖动开始时通过求鼠标点击位置与旋转支点的XY求tanY/X得到当前鼠标的角度，然后在拖动继续时求新的角度。我没有理解的地方是为什么使用原来的角度减去新的角度，旋转的时候角度不是在不断变大吗，这样的话传入Rotate的值就是一个负值，但游戏中旋转是正常的，并且不管怎么旋转始终是在0-359度之间。是我理解错误了吗？

Answer 1

Rotate(angle) 当前角度旋转 angle度
angleToMouse求出来仅是基于0的角度
需要使用旧的 - 新的 得到偏移角度