Question Confusing bug

In my game, the player is able to rotate their gravity in a corridor platformer, which in turn Lerps the player's rotation to the right rotation for upright. the way I'm doing this is by checking whether the z-axis (the only bit that isn't just set to the player's rotation based on a camera movement script) is the same as the target z-axis, and if it isn't, I'm lerping it so that it is.

The issue, however, is that when I have changed the player's rotation once, it stops the player's y rotation from changing, thus stopping you from looking to the side entirely.

All relevant code:

Code (CSharp):

1. Quaternion GravRotation;
2.  
3. void Update()
4.     {
5.         if(Input.GetKeyDown("q"))
6.         {
7.             if(GravityState < 4)
8.             {
9.                 GravityState++;
10.             }
11.             else
12.             {
13.                 GravityState = 1;
14.             }
15.             GravChange();
16.         }
17.         if(Input.GetKeyDown("e"))
18.         {
19.             if(GravityState > 1)
20.             {
21.                 GravityState--;
22.             }
23.             else
24.             {
25.                 GravityState = 4;
26.             }
27.             GravChange();
28.         }
29.     }
30.  
31.     void GravChange()
32.     {
33.         if(GravityState == 1)
34.         {
35.             Physics.gravity = new Vector3(0f, -12.5f, 0f);
36.             GravRotation = Quaternion.Euler(PlayerTransform.rotation.x, PlayerTransform.rotation.y, 0);
37.         }
38.         if(GravityState == 2)
39.         {
40.             Physics.gravity = new Vector3(-12.5f, 0f, 0f);
41.             GravRotation = Quaternion.Euler(PlayerTransform.rotation.x, PlayerTransform.rotation.y, -90);
42.         }
43.         if(GravityState == 3)
44.         {
45.             Physics.gravity = new Vector3(0f, 12.5f, 0f);
46.             GravRotation = Quaternion.Euler(PlayerTransform.rotation.x, PlayerTransform.rotation.y, 180);
47.         }
48.         if(GravityState == 4)
49.         {
50.             Physics.gravity = new Vector3(12.5f, 0f, 0f);
51.             GravRotation = Quaternion.Euler(PlayerTransform.rotation.x, PlayerTransform.rotation.y, 90);
52.         }
53.     }
54.  
55.  
56.     void FixedUpdate()
57.     {
58.         if (PlayerTransform.rotation.z != GravRotation.z)
59.         {
60.             PlayerTransform.rotation = Quaternion.Lerp(PlayerTransform.rotation, GravRotation, 10f);
61.         }
62.      }

All help appreciated, thanks!

 

Pretty sure this is gimbal lock. To see what I mean:

- put a cube in a blank scene
- using the inspector, independently rotate it a little bit around x, y, z - works as expected
- now set x rotation to 90
- try rotate around y and z - note that z works identically to y rotation! You can no longer rotate z!

In the context of your game, I'm not sure what the best solution would be, but there's a few possibilities. Check out some youtube tutorials on changing gravity controllers...

 

I'll be honest I didn't even know this was a thing, I'll look into some tutorials then, thanks!

 

please do, because this is very basic, and the primary motivator for the quaternions instead of Euler angles.