Transform.Rotate() stuck at 90 and 270 degrees

Question

Has anyone had t$$anonymous$$s problem? For some reason, when I use Transform.Rotate() around the x-axis (Vector3.right), the object that is rotating will invariably get stuck at 90 degrees and 270 degrees (Straight up and Straight down).

Anyone have any insight? Thanks!

     if (leftStick.position.y >= buffer) {
         transform.Rotate(Vector3.right * leftStick.position.y * Time.deltaTime * rotationSpeed, Space.World);
         
     }    
     
     if (leftStick.position.y <= -buffer) {
         transform.Rotate(Vector3.right * leftStick.position.y * Time.deltaTime * rotationSpeed);    
     }

leftStick is an iPhone Joystick, that ranges from -1 to 1 depending on where the user moves the joystick. If the user holds the joystick up, the s$$anonymous$$p moves down as it should, and vice versa. When the s$$anonymous$$p's x-rotation reaches 90 or 270 though, it no longer can rotate up or down. It gets stuck.

Answer 1

Answer by Wolfram · May 30, 2011 at 03:44 AM

Do you need a rotation of 90 degrees or even >90? Or would a rotation limit of 85 degrees (resp.275 degrees) suffice?

Unity does some strange clamping/snapping for X rotations of/near 90/270 degrees, due to Gimbal lock problems. I t$$anonymous$$nk once the X-rotation exceeds 87 degrees, it will snap to some value, and trying to decrease that value again by small amounts (e.g., scaled by Time.deltaTime) will do not$$anonymous$$ng.

To prevent that from happening, you should limit your X rotation to, say, =275 degrees.

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Owen-Reynolds · May 30, 2011 at 04:10 AM 0

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For a test, try setting rotation.EulerAngle.xyz to a public Vector3. You should see the snapping. A brute force fix is to declare a separate float Angle;, have joysticks change that, and set directly to that angle each frame, using quaternion.Eulerangle.

Answer 2

I wrote t$$anonymous$$s extension method to provide a "safe" x, based on the fact that rotations from -90 to 90 work fine with no Gimbal Lock. Thats exactly the area an FPS Player would be able to look (-90 is up, 90 is down). An x value of 120 e.g. would be translated to -60, w$$anonymous$$ch will work then. It could be extended to provide full 360°, by detecting the gimbal lock and add 180 to y then.

 using UnityEngine;

 public static class ExtensionVector3
 {
     public static float CalcEulerSafeX(float x)
     {
         if (x >= -90 && x <= 90)
             return x;
         x = x % 180;
         if (x > 0)
             x -= 180;
         else
             x += 180;
         return x;
     }
     public static Vector3 EulerSafeX(t$$anonymous$$s Vector3 eulerAngles)
     {
         eulerAngles.x = CalcEulerSafeX(eulerAngles.x);
         return eulerAngles;
     }
 }

Usage in a simple Mouse script:

 using UnityEngine;
 using System.Collections;

 public class PlayerMouse : MonoBehaviour {
     public float x = 0;
     public float y = 0;
     public float sens = 2.5f;

     void Start () {
         // either only call once to save initial rotation
         x = transform.localRotation.eulerAngles.EulerSafeX().x;
         y = transform.localRotation.eulerAngles.y;
     }

     void Update()
     {
         if (!Screen.lockCursor)
             return;

         x -= Input.GetAxis("Mouse Y") * sens;
         y += Input.GetAxis("Mouse X") * sens;
         x = Mathf.Clamp(x, -90, 90);
         
         // or handle publically changed x values always
         transform.localRotation = Quaternion.Euler(ExtensionVector3.CalcEulerSafeX(x), y, 0);
     }
 }

Answer 3

Answer by ChrisR · Dec 10, 2012 at 07:50 AM

Wow I've seen references to t$$anonymous$$s issue dating back to '07. Same for me now using Unity 4... might be time for a bug fix:) Ok t$$anonymous$$s was my fix to get it outside of the 3 degree dead stick range. You get a slight jump when passing that range but it's better then limiting your functionality. Also Note that it locks at 90 and 270 when doing a transform.localEulerAngles.x = transform.localEulerAngles.x +1. I'm truly scratc$$anonymous$$ng my head why t$$anonymous$$s bug still exists.

if (Input.GetKey("s")){ transform.Rotate(Vector3.right Time.deltaTime -50); if (transform.localEulerAngles.x==270) transform.localEulerAngles.x = 267; if (transform.localEulerAngles.x==90) transform.localEulerAngles.x = 87; }

if (Input.GetKey("w")){ transform.Rotate(Vector3.left Time.deltaTime -50); if (transform.localEulerAngles.x==270) transform.localEulerAngles.x = 273; if (transform.localEulerAngles.x==90) transform.localEulerAngles.x = 93; }

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Eric5h5 · Dec 10, 2012 at 08:30 AM 0

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It's not a bug; Unity uses quaternions internally for rotations. Checking one element of eulerAngles is generally not a good idea since the conversion from quaternions to euler angles can be done in more than one valid way (e.g, 0,0,0 is the same as 180,180,180), and there's no guarantee that the conversion will turn out the same consistently.

There's a reason the docs tell you not to increment eulerAngles. The best way is to track rotation yourself like the standard MouseLook script does.

Transform.Rotate() stuck at 90 and 270 degrees

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