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Bug setting transform.rotation = Quaternion.Euler(0,180,180) is inconsistent

Discussion in 'Editor & General Support' started by SoftwareGeezers, Aug 30, 2020.

  1. SoftwareGeezers


    Jun 22, 2013
    I have issues with disappearing sprites in a 2D space shooter that I've traced to different behaviour with assigning a rotation to point straight down. (Unity 2019.2)

    In a simple test project,
    Code (CSharp):
    1. transform.rotation = Quaternion.Euler(0,180,180)
    ...results in a rotation of Euler (180,0,0) and the sprite is rotated and visible.

    However, in my game, the same code results in a rotation of Euler(0,180,180) and my sprite is flipped and invisible.

    This affects the underlying mechanics of transform manipulation. To date, I've been assigning transform directions using
    Code (CSharp):
    1. transform.up = direction
    . I have had some issues with flashing sprites, disappearing for a frame, that I hadn't bothered to trace up till now as I thought it was related to hidden collisions, but my current work of orbiting objects around other objects has resulted in this discovery that transform.up = direction is inconsistent when pointing straight down. transform.up = Vector3.down on some objects results in a (0,0,180) rotation, while on others, a (0,180,180) rotation.

    I have been unable to create a repo case. Simple sprites in my game in test scene work correctly, with a direct facing down being drawn (and the rotation being set to Euler(180,0,0)), even with rigidbodies and colliders attached, but the same code on my objects in game is problematic. I guess it must be something to do with instantiating and parenting and who-knows-what.

    Are Unity aware of any issues? Is this a bug requiring a submission? It's not a particularly easy submission for a bug report.

    Edit: I have a workaround. I test if the quarternion rotation is down, and if so, set it as down from euler instead of assigning the rotation directly.

    Code (CSharp):
    1.     private void Start() {
    2.         bugPatchRotation = Quaternion.FromToRotation(Vector3.up, Vector3.down);
    3.     }
    5.     private void Update() {
    7.        targetRotation = Quaternion.FromToRotation(Vector3.up, direction);
    8.        if (targetRotation == bugPatchRotation) {
    9.            _trans.rotation = Quaternion.Euler(0, 0, 180);
    10.            print("down"+ _trans.rotation.eulerAngles);
    11.        } else {
    12.            _trans.rotation = targetRotation;
    13.        }
    Note that assigning this
    _trans.rotation = Quaternion.Euler(0, 0, 180);
    results in transform rotation (0,0,180), but assigning this:
    _trans.rotation = Quaternion.Euler(180, 0, 0);
    results in transform rotation (0,180,180).

    That is, this transform behaves differently to other transforms in how it deals with 180 degree rotations.
    Last edited: Aug 30, 2020