使用C＃在Unity 3d中使用触摸旋转游戏对象

Question

I'm rotating a GameObject based on 2 finger touch. I have the rotate working fine, but I'm getting a strange issue where sometimes I will touch with two fingers to start the rotate, but as soon as I touch the screen the object will instantly rotate. This seems to be random as to when it does it, and the rotation also appears to be random. I'm thinking that the touch is triggering the rotate based on the last position, but my code should be resetting the start position.

The touch code is in a script attached to the object to rotate, so it's all in one file.

Here's the code.

In the Update method I detect that it's touch supported and attempt to call "HandleTouch()"

void Update()
{
    if (Input.touchSupported)
        HandleTouch();
    else
        HandleMouse();
}

The HandleTouch method

private void HandleTouch()
{
    if (Input.touchCount < 2) return;
    switch (Input.touchCount)
    {
        case 2:
            Touch touch = Input.GetTouch(0);
            if (touch.phase == TouchPhase.Began)
            {
                lastRotPosition = touch.position;
            }
            else if (touch.phase == TouchPhase.Moved)
            {
                Vector3 offset = touch.position - lastRotPosition;
                lastRotPosition = touch.position;
                RotateCamera(offset.x * RotateSpeedTouch, offset.y * RotateSpeedTouch);
            }
            else if (touch.phase == TouchPhase.Ended)
            {
                lastRotPosition = new Vector2();
            }
            break;
    }
}

And this is the method that rotates the GameObject

void RotateCamera(float x, float y)
{
    float rotX = x * rotateSpeed * Mathf.Deg2Rad;
    float rotY = y * rotateSpeed * Mathf.Deg2Rad;
    transform.Rotate(Vector3.up, rotX);
    transform.Rotate(Vector3.right, -rotY);
}

Thank you for any help or insight you might offer.

Answer 1

You aren't tracking the fingerId

As touches may not be stored in the same order:

Furthermore, the continuity of a touch between frame updates can be detected by the device, so a consistent ID number can be reported across frames and used to determine how a particular finger is moving.

...the fingerId property can be used to identify the same touch between frames.

So when a new finger touches the screen your code may see this:

• first finger touches, touch count 1, skip code
• second finger touches, it is the second finger in the array, touch count 2, begin processing:
  • the first touch has the phase TouchPhase.Moved
  • lastRotPosition is currently zero (due to either the default value or due to a previous TouchPhase.Ended )
  • touch.position - lastRotPosition evaluates to non-zero (big rotation occurs)

When it works correctly you get this:

• first finger touches, touch count 1, skip code
• second finger touches, it is the first finger in the array, touch count 2, begin processing:
  • the first touch has the phase TouchPhase.Begin
  • lastRotPosition is updated to the touch's location
  • next frame the touch.position - lastRotPosition evaluates to near-zero (small rotation occurs)