Player falling through the floor

Questions & Answers
1

I have started a new Unity project and created a player with PlayerController script.
When I hit play, my player starts falling through the floor and after a few seconds it teleports up, to where it started falling. The floor, has a box collider and my player has a capsule collider and a rigidbody (both colliders have the isTrigger boolean set to false and they are both in the Default layer). I am using the same controller script I always use in my projects (unless I made a mistake and can’t find it).
Here’s that script:

    public class PlayerController : MonoBehaviour
    {
        public Rigidbody playerRigidbody;
        public Camera playerCamera;
        public float speed = 3f;
        public float mouseSensitivity = 5f;
        public Vector3 cameraOffset = Vector3.zero;
        private Vector3 playerPosition = Vector3.zero;
        private Vector3 playerRotation = Vector3.zero;
        private Vector3 cameraRotation = Vector3.zero;
    
        void Start()
        {
            playerRigidbody = GetComponent<Rigidbody>();
    
            playerPosition = playerRigidbody.position;
            playerRotation = playerRigidbody.rotation.eulerAngles;
            cameraRotation = playerCamera.transform.localEulerAngles;
        }
    
        void Update()
        {
            CalculateMovement();
            playerCamera.transform.position = playerRigidbody.position + cameraOffset;
        }
    
        void FixedUpdate()
        {
            playerRigidbody.MovePosition(playerPosition);
            playerRigidbody.MoveRotation(Quaternion.Euler(playerRotation));
    
            playerCamera.transform.localEulerAngles = cameraRotation;
        }
    
        void CalculateMovement()
        {
            Vector3 xVel = transform.right * Input.GetAxis("Horizontal");
            Vector3 zVel = transform.forward * Input.GetAxis("Vertical");
            playerPosition += (xVel + zVel) * speed * Time.fixedDeltaTime;
            Debug.Log((xVel + zVel) * speed * Time.fixedDeltaTime);
    
            float xRot = -Input.GetAxis("Mouse Y");
            float yRot = Input.GetAxis("Mouse X");
            playerRotation += new Vector3(0f, yRot, 0f) * mouseSensitivity;
            cameraRotation += new Vector3(xRot, yRot, 0f) * mouseSensitivity;
        }
    }

As you can see I’ve included a Debug.Log(), but it always prints 0.0 on the y axis.

EDIT:
I have removed the PlayerCotroller and the falling is not happening anymore, so there’s something wrong with it.
I would be very happy if you’d help me find the error.

2

The slow movement downward was due to gravity, but it wasn’t able to build up since you were using moveposition each frame without accounting for it. I prefer just setting the rigidbody.velocity directly. Hope this helps.

public class PlayerController : MonoBehaviour {
    public Rigidbody playerRigidbody;
    public Camera playerCamera;
    public float speed = 3f;
    public float mouseSensitivity = 5f;
    public Vector3 cameraOffset = Vector3.zero;
    private Vector3 playerRotation = Vector3.zero;
    private Vector3 cameraRotation = Vector3.zero;

    void Start() {
        playerRigidbody = GetComponent<Rigidbody>();

        playerRotation = playerRigidbody.rotation.eulerAngles;
        cameraRotation = playerCamera.transform.localEulerAngles;
    }

    void Update() {
        CalculateMovement();
        playerCamera.transform.position = playerRigidbody.position + cameraOffset;
    }

    Vector3 xVel;
    Vector3 zVel;
    void CalculateMovement() {
        xVel = transform.right * Input.GetAxis("Horizontal");
        zVel = transform.forward * Input.GetAxis("Vertical");

        float xRot = -Input.GetAxis("Mouse Y");
        float yRot = Input.GetAxis("Mouse X");
        playerRotation += new Vector3(0f, yRot, 0f) * mouseSensitivity;
        cameraRotation += new Vector3(xRot, yRot, 0f) * mouseSensitivity;
    }

    void FixedUpdate() {
        float yVel = playerRigidbody.velocity.y;
        playerRigidbody.velocity = (xVel + zVel) * speed + Vector3.up * yVel;

        playerRigidbody.MoveRotation(Quaternion.Euler(playerRotation));

        playerCamera.transform.localEulerAngles = cameraRotation;
    }

}