Issue with Jumping

Question

In my game, you have to press (or more accurately release) space bar to jump. However, at seemingly random instances the player wouldn't jump. So it is working fine most of the times but then out of nowhere, the cube doesn't jump even when input is given. Please help!

    public float horizontalSpeed = 0.5f;
    Rigidbody rb;
    public float JumpHeight = 10f;
    private bool onGround;
    public float forwardSpeed;
    public float rotSpeed;


    private float increaseJumpBy = 1f;
    private bool increaseJumpHeight;
    private bool jumped = false;

    public SimpleHealthBar healthBar;

    private float Horizontal;
    private float Forward;
    Vector3 forwardMovement;
    Quaternion verRotation;
    Vector3 horizontalmovement;

    public float maxJump;


    // Use this for initialization
    void Start()
    {
        rb = GetComponent<Rigidbody>();
        onGround = true;
        Forward = Time.deltaTime * forwardSpeed;
        forwardMovement = new Vector3(0f, 0f, Forward);
        verRotation = Quaternion.Euler(rotSpeed * Time.deltaTime, 0f, 0f);           
    }

    private void FixedUpdate()
    {
        rb.MovePosition(transform.position + forwardMovement);

        Jump();
    }
    // Update is called once per frame
    void Update()
    {
        healthBar.UpdateBar(JumpHeight, maxJump);   
    }

    void Jump()
    {
      //Debug.Log("Jumpheight" + JumpHeight);

        if(onGround)
        {

            if (Input.GetKeyDown(KeyCode.Space) || Input.GetKeyDown(KeyCode.UpArrow))
            {
                if (JumpHeight < maxJump)
                {
                    increaseJumpHeight = true;
                }
            }

            if(JumpHeight>= maxJump)
            {
                JumpHeight = maxJump;
            }

            if (increaseJumpHeight)
            {
                JumpHeight += increaseJumpBy;
            }

            if (Input.GetKeyUp(KeyCode.Space) || Input.GetKeyUp(KeyCode.UpArrow))
            {
                rb.velocity = new Vector3(0f, JumpHeight, 0f);
                onGround = false;
                increaseJumpHeight = false;
                jumped = true;               
            }

            if (jumped)
            {
                JumpHeight = 0;
                jumped = false;
            }        
        }

        if (!onGround)
        {               
            Horizontal = Input.GetAxis("Horizontal");
            horizontalmovement = new Vector3(Horizontal * horizontalSpeed * Time.deltaTime, 0f, 0f);
            rb.MovePosition(transform.position + horizontalmovement + forwardMovement);
            Quaternion horRotation = Quaternion.Euler(0f, 0f, Horizontal * horizontalSpeed * Time.deltaTime);

            rb.MoveRotation(rb.rotation * verRotation /*horRotation*/);            
        }        
    }
    void OnCollisionEnter(Collision collision)
    {
        onGround = true;
    }
    void OnCollisionExit(Collision col)
    {
        onGround = false;
    }

Edit: Removing the bool jumped and adding JumpHeight = 0 to if(!onGround) seems to solve the problem

Answer 1

Your code for capturing input using Input.GetKeyDown should be called from Update, not FixedUpdate.

It's possible for input events to be missed if it happens between two FixedUpdate calls. FixedUpdate does not necessarily fire every frame. For example, 2 Update calls might fire consecutively before a FixedUpdate fires.

(Note that you should still use FixedUpdate when dealing with RigidBody, as you have done already.)

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(For more information, see this discussion on Unity Answers: "Is Input detection ok to do in fixedupdate?" or other similar questions here like this one: Unity Input.GetMouseButtonDown(0) is not working.)

Answer 2

Removing the bool jumped and adding JumpHeight = 0 to if(!onGround) seems to solve the problem