X-Flip is making my rotation break?

Questions & Answers
1

Hi, I’m trying to make a twin-stick player like in Nuclear Throne, meaning a side-facing sprite with a gun that rotates around him 360 degrees. The graphics x-flip when past 90/-90 degrees, but the x-flip/angle combo isn’t working as I’d expect…

The gun’s image (on a quad) is a child of my “gun” object, which is the game object I apply the rotation to. In the normal orientation, the “gun” is positioned at the arm-pivot point, and rotation happens around this point just fine.

When flipped, the gun rotates from a weird random pivot (not on the arm). When I look at everything in the scene view, the gun is at the correct arm-pivot point, like it should work. This is the confusing part if I change the angle of the gun object by a tiny amount (0.00001) in the properties window it snaps into the correct position and orientation.

So I don’t see any issues with the math, and unity “fixes” it when I edit the angle directly in the properties window - any ideas why the rotation gets messed up in-game?

(note: While looking for an answer, I only found the suggestion to rotate around the Y-axis instead. I’d prefer to not do this for a variety of reasons, including my quads disappearing and my z-ordering getting flipped.)

EDIT: Since you asked, here’s some code. It’s split between two scripts (one for the character, another for the gun). Here’s the character’s x-flip code, the facex var is created from the inputs, so you face the way you are moving/shooting. FlipX is a constant with values (-1, 1, 1).

if (facex != 0 && facex > 0 != transform.localScale.x > 0)
    transform.localScale = Vector3.Scale(transform.localScale, FlipX);

And here’s the code on the weapon which rotates it (and its child with the image quad).

float ang = Mathf.Rad2Deg * Mathf.Atan2(aim.y, aim.x);
if(ang > 90 || ang < -90)
    ang = Mathf.Sign(ang) * 180 - ang;
Quaternion q = Quaternion.AngleAxis(ang, Vector3.forward);
transform.rotation = q;

I think the math is correct, because as I pointed out things get ‘fixed’ when I enter identical values at runtime in the inspector. It’s almost like there is some kind of Apply() method I need to call… but that isn’t the case right?

2

Hopefully someone can come up with a better solution than this, but I managed to fix it using a trick I saw here: Rendering Bug? - Negative ScaleX + Rotation

Every frame, I can do this on my weapon script and it makes everything work the way it is supposed to work.

            gameObject.SetActive(false);
            gameObject.SetActive(true);

Of course, this incurs a performance hit averaging around .35ms according to stopwatch. So if I need to animate 12+ networked players using this code, it will probably not be a viable solution. Any real solution would be appreciated!!!

3

Same problem. Have parent object with x scale = -1. Want to set child positions and rotations, but positioning is not mirrored, and rotations get broken. My work-around is: before updating child rot/pos set the parent scale to 1,1,1 then set child rot/pos, then set parent scale to -1,1,1 which then properly mirrors all children. Using Unity 5.4.