Irregular iOS Touch Rate on iPhone - ios

Question

I posted this question three days ago, but I received the feedback that the question was not clear so I would like to ask again. Also, the scope of the problem has changed as I researched it further (no Unity issue!)
I'm making a game for iOS where you rotate an object left and right by touching the left or right side of the screen. The Object rotates as long as the display is touched and stops rotating when the touch ends. When I run the game on an actual iPad/iPhone for a while every few touches the Rotation of the Objects stutters for about 2 seconds. This happends in about 5% of the touches. All other touches work perfectly smooth.
All other Game Actions work fine at the set frame rate of 60 fps. The only thing that doesn't move smoothly is the rotated object, while the rest of the game is all running perfectly smooth. I tried to visualize the problem on the attached image. See here
It visually looks like the Touch Refresh Rate is freezed for two seconds.
What may be the cause for this and how do I fix this?
I created the game with the game engine Unity. I use these versions:
- Unity: 2019.3.15f1
- Xcode: 11
- Device: iPhone x
- iOS Version: 13.5.1
After a lot of research I found out, that this is not an issue related to Unity. Also, there is no issue when building the game on an Android device.
Steps to reproduce:
int rotation
private void FixedUpdate(){
for (int i = 0; i < Input.touchCount; i++)
{
Vector3 touchPos = Camera.main.ScreenToWorldPoint(Input.touches[i].position);
if (touchPos.x < 0)
{
rotation += 10;
}
else if (touchPos.x > 0)
{
rotation -= 10;
}
}
transform.Rotate(0, 0, rotation);
rotation = 0;
}
Coding the Touch Input via c# in Unity (see above)
Building the Project on iOS Platform (creating an xcodeproject)
Open the Project in XCode and running it on the iPhone
Does anybody have a solution for this?

Answer 1

Any "Input" class should be called in Update(), instead of FixedUpdate().
The Input data loss is expected if you are trying to get them in FixedUpdate().
Just for example, FixedUpdate can be execute twice in one frame, or skipped in one frame. That's how it causes data lost or inaccurate.
The proper solution will be sth like below.
int rotation
private void Update()
{
for (int i = 0; i < Input.touchCount; i++)
{
Vector3 touchPos = Camera.main.ScreenToWorldPoint(Input.touches[i].position);
if (touchPos.x < 0)
{
rotation += 10 * time.deltaTime;
}
else if (touchPos.x > 0)
{
rotation -= 10 * time.deltaTime;
}
}
transform.Rotate(0, 0, rotation);
rotation = 0;
}
and please be noted that your current rotation direction is determined by a ray casting from camera.
If you want to rotate left/right by screen space, this should work better.
private void Update()
{
int rotation = 0;
for (int i = 0; i < Input.touchCount; i++)
{
if (Input.touches[i].position.x < Screen.width/2)
{
rotation += 10 * time.deltaTime;
}
else
{
rotation -= 10 * time.deltaTime;
}
}
transform.Rotate(0, 0, rotation);
}
In general, I prefer a simple rotation script by checking last touch.
private void Update()
{
if(Input.touchCount > 0)
{
if (Input.touches[Input.touchCount-1].position.x < Screen.width/2)
{
transform.Rotate(0, 0, 10f * time.deltaTime);
}
else
{
transform.Rotate(0, 0, -10f * time.deltaTime);
}
}
}
Or, if you really want to sync the input with FixedUpdate(), you can do sth like below.
bool HasTouch = false;
float SpeedRot = 0;
private void Update()
{
if(Input.touchCount > 0)
{
HasTouch = true;
if (Input.touches[Input.touchCount-1].position.x < Screen.width/2)
{
SpeedRot = 10f;
}
else
{
SpeedRot = -10f;
}
}
else
{
HasTouch = false;
}
}
private void FixedUpdate()
{
if(HasTouch) transform.Rotate(0, 0, SpeedRot * Time.fixedDeltaTime);
}