Bug Weird behavior, rotation speeds up

Hi everyone,

I'm making this "laser aim" effect that follows the player, but it seems to "snap" to the player and disregard the maximum rotate speed. I don't know what's going on here:



Here code:

Code (CSharp):

1. // This happens on LateUpdate
2. transform.rotation = Quaternion.RotateTowards(transform.rotation, GetFollowPlayerRotation(), turnSpeed * Time.deltaTime);
3.  
4. private Quaternion GetFollowPlayerRotation()
5. {
6.     float angle = Vector3.SignedAngle(Vector3.down, (followTarget.position - transform.position).normalized, Vector3.forward);
7.     Quaternion rotationToTarget = Quaternion.Euler(0, 0, angle);
8.     return rotationToTarget;
9. }
10.  

 

when transform of the player gets close to the beam, your math seems to broke down,
here is what would I do,

- i would debug.log the "angle" variable to see whats going on in there.
- after i collect enough information about the variable, i come to a conclusion about why it acts that why,
- then i fix my code accordingly.

 

Hi, thanks for replying

Debugging the angle itself didn't help, but it led me on a path, and I think I've determined that the Quaternion.RotateTowards function is bugged.
Testing showed that, for tiny angle differences (about 0.16 degrees or less), RotateTowards ignores the maxDegreesDelta parameter and rotates the full angle difference.

Here's my debugging code:

Code (CSharp):

1. turnSpeed = 5;
2. Quaternion followRotation = GetFollowPlayerRotation();
3. rotation = Quaternion.RotateTowards(transform.rotation, followRotation, turnSpeed * Time.deltaTime);
4.  
5. Debug.Log("actual turn speed: " + (rotation.eulerAngles.z - transform.rotation.eulerAngles.z) / Time.deltaTime +
6.     "\n\ntransform angle: " + transform.rotation.eulerAngles.z +
7.     "\nfollow angle: " + followRotation.eulerAngles.z +
8.     "\n\ndifference: " + Mathf.Abs(transform.rotation.eulerAngles.z - followRotation.eulerAngles.z) +
9.     "\nturnSpeed * dTime: " + turnSpeed * Time.deltaTime +
10.     "\n\nexpected change: " + Mathf.Min(Mathf.Abs(followRotation.eulerAngles.z - transform.rotation.eulerAngles.z), turnSpeed * Time.deltaTime) +
11.     "\nactual change: " + Mathf.Abs(rotation.eulerAngles.z - transform.eulerAngles.z) +
12.     "\n");
13.  

Here's the output of a correct rotation when the player is far from the beam:



And here's the output of a "snapped" rotation. Notice how the function returned exactly the angle difference, which is bigger than maxDegreesDelta:



I suppose I should file a bug report and perform the rotation manually.

 

Are you in 2D or 3D ?

 

So I ditched Quaternion.RotateTowards and went with the following code, which works great:

Edit: nope, I failed to account for the change from 360° to 0°. Will update code

 

Okay so here's the code that actually works:

Code (CSharp):

1. // rotation = Quaternion.RotateTowards(transform.rotation, GetFollowPlayerRotation(), turnSpeed * Time.deltaTime);
2.  
3. float angleBetween = GetFollowPlayerRotation().eulerAngles.z - transform.rotation.eulerAngles.z;
4. if (angleBetween < -180) angleBetween += 360;
5. else if (angleBetween > 180) angleBetween -= 360;
6.  
7. float maxTurn = turnSpeed * Time.deltaTime;
8. float actualTurn = Mathf.Clamp(angleBetween, -maxTurn, maxTurn);
9. rotation = transform.rotation * Quaternion.Euler(0, 0, actualTurn);
10.  

 

Hi there, this project is in 2d