Problem with Unity’s FPSController camera

The reason for this is the way cursors are handled for cameras in this way. What happens behind the scene is the cursor is locked to the center of the screen. Each frame, the engine takes the amount of movement from the center and applies that to the input axes you query, then resets the mouse to the center of the screen. On the first frame of your game though, the mouse isn't anywhere near the center of the screen, so it sees that as a massive quick jerky move, and applies it as such. The best way to correct it would be to disable the mouselook script for the first few frames which, being a fraction of a second, should be unnoticable to players, and will eliminate the jerk motion.

@FortisVenaliter

Clamping the yRot and xRot worked! I’ve figured out how to get rid of the jerk and still be able to “whip” the camera!

For anyone who also has this problem, here’s the modified code:

 using System;
 using UnityEngine;
 using UnityStandardAssets.CrossPlatformInput;
 
 namespace UnityStandardAssets.Characters.FirstPerson
 {
     [Serializable]
     public class MouseLook
     {
         public float XSensitivity = 2f;
         public float YSensitivity = 2f;
         public bool clampVerticalRotation = true;
         public float MinimumX = -90F;
         public float MaximumX = 90F;
         public bool smooth;
         public float smoothTime = 5f;
 
 
         private Quaternion m_CharacterTargetRot;
         private Quaternion m_CameraTargetRot;
         private bool clamped = true;
 
         public void Init(Transform character, Transform camera)
         {
             m_CharacterTargetRot = character.localRotation;
             m_CameraTargetRot = camera.localRotation;
         }
 
 
         public void LookRotation(Transform character, Transform camera)
         {
             float yRot = CrossPlatformInputManager.GetAxis("Mouse X") * XSensitivity;
             float xRot = CrossPlatformInputManager.GetAxis("Mouse Y") * YSensitivity;
 
             if(clamped)
             {
                 if(yRot != 0) yRot = 0;
                 if(yRot != 0) yRot = 0;
             }
 
             if(yRot != 0 || xRot != 0)
             {
                 clamped = false;
             }
 
             m_CharacterTargetRot *= Quaternion.Euler (0f, yRot, 0f);
             m_CameraTargetRot *= Quaternion.Euler (-xRot, 0f, 0f);
 
             if(clampVerticalRotation)
                 m_CameraTargetRot = ClampRotationAroundXAxis (m_CameraTargetRot);
 
             if(smooth)
             {
                 character.localRotation = Quaternion.Slerp (character.localRotation, m_CharacterTargetRot,
                     smoothTime * Time.deltaTime);
                 camera.localRotation = Quaternion.Slerp (camera.localRotation, m_CameraTargetRot,
                     smoothTime * Time.deltaTime);
             }
             else
             {
                 character.localRotation = m_CharacterTargetRot;
                 camera.localRotation = m_CameraTargetRot;
             }
         }
 
 
         Quaternion ClampRotationAroundXAxis(Quaternion q)
         {
             q.x /= q.w;
             q.y /= q.w;
             q.z /= q.w;
             q.w = 1.0f;
 
             float angleX = 2.0f * Mathf.Rad2Deg * Mathf.Atan (q.x);
 
             angleX = Mathf.Clamp (angleX, MinimumX, MaximumX);
 
             q.x = Mathf.Tan (0.5f * Mathf.Deg2Rad * angleX);
 
             return q;
         }
 
     }
 }

BTW I couldn’t find anything like SetMousePosition(), maybe the static function you were thinking of is from an older version of Unity?