Rotate Child GameObject Over Time

Question

Good Morning All,

I have a character gameobject with a few child gameobjects that lead to the sprite.

• Character

• Character Rotator

• Sprite Holder

I have been flipping the character like this depending on if left or right is pressed and it's worked fine:

// Flip the player's sprite based on input and x vector
        if (myVector.x < 0 && facingRight)
        {
            facingRight = !facingRight;
            // childToRotate is Character Rotator
            hildToRotate.transform.localRotation = Quaternion.Euler(0, 180, 0);
        }

        if (myVector.x > 0 && !facingRight)
        {
            facingRight = !facingRight;
            // childToRotate is Character Rotator
            childToRotate.transform.localRotation = Quaternion.Euler(0, 0, 0);
        }

Now, I want to rotate the character 180 degrees over time, rather than it being an instant flip. ( Just like in Paper Mario games )

This was my attempt at creating the effect:

public IEnumerator RotateCharacterModel()
    {
        float startRotation = childToRotate.transform.eulerAngles.y;
        float endRotation = startRotation + 180f;
        float t = 0.0f;
        float duration = .3f;
        while (t < duration)
        {
            t += Time.deltaTime;
            float yRotation = Mathf.Lerp(startRotation, endRotation, t / duration) % 180.0f;

         // this is where I need to rotate the "Character Rotator's" local rotation but I am struggling...

        }
        _characterIsRotating = false;
    }

I think I'm very close, I just need assistance replacing the last comment with code that rotates the "Character Rotators" local rotation.

Any assistance with this would be immensely appreciated! Thank you for taking the time!

Answer 1

Interpolating Euler angles is fraught. You'll generally get more intuitive behaviour with fewer confusing edge cases by expressing your orientations as Quaternions, and interpolating those:

public IEnumerator RotateCharacterModel()
{
    Quaternion startRotation = childToRotate.transform.rotation;
    // Rotate start by 180 degrees on the world y axis.
    Quaternion endRotation = Quaternion.Euler(0, 180, 0) * startRotation;

    float duration = .3f;
    // Thinking of this as a speed saves a division every step.
    float speed = 1f/duration;

    // Use a for loop instead of a while, 
    // that way all your loop variable stuff stays together.
    for (float t = 0; t < 1f; t += speed * Time.deltaTime)
    {
        childToRotate.transform.rotation = Quaternion.Lerp(
                                                 startRotation,
                                                 endRotation,
                                                 t
                                           );
    }
    // Snap to the final orientation (loop can end with spare change left over)
    childToRotate.transform.rotation = endRotation;
    _characterIsRotating = false;
}