Unity infinite loop of moving sprites (Slot Machine reel)

Question

I'm trying to make a slot machine prototype. My goal is to simulate(programmatically) symbols movement. I want my symbols move down and when each symbol go out of game field, it should be moved to the frame's top again. Here is my code:

public class Reel : MonoBehaviour {

    public int reelHeight = 3;

    public int symbolWidth = 3;
    public int symbolHeight = 3;

    public float reelSpeed = 1000;

    [SerializeField]
    public GameObject symbol;

    public List<GameObject> symbols = new List<GameObject>();

    private bool inSpin = false;

    void Start () {
        // reel predefined symbols
        int[] reelSymbols = new int[] { 0, 0, 0, 0, 1, 2, 1, 3, 4, 5}; //{0,0,0,0,1,1,1,2,2,3,3,3,4,4,4,4,1,5,5,5,5,2,2,6,6,6,6,3,7,7,7,7};

        // instantiating symbols on reel
        for (int i = 0; i < reelSymbols.Length; i++) {
            symbol = Instantiate (symbol, new Vector3 (0, i*symbolHeight, 0), Quaternion.identity);
            symbol.GetComponent<Symbol>().symbolType = reelSymbols [i];
            symbols.Add (symbol);
        }
    }

    public void SpinReel () {
        inSpin = !inSpin;
    }

    void Update () {
        // infinite spin
        if (inSpin) {
            foreach (GameObject symbol in symbols) {
                // moving symbols down
                float currentReelSpeed = reelSpeed * Time.deltaTime;
                symbol.transform.Translate(Vector3.down * currentReelSpeed);

                // move symbol up to the top if it's go down and no longer vidible
                if (symbol.transform.position.y <= -3.0f) {
                    float newY = ((symbols.Count - 1) * symbolHeight) + transform.position.y;
                    symbol.transform.position = new Vector3 (transform.position.x, symbols.Count*symbolHeight, transform.position.z);
                }
            }
        }
    }
}

My symbol is a regular GameObject:

public class Symbol : MonoBehaviour {

    public Sprite [] sArray;

    public int symbolType;

    // Use this for initialization
    void Start () {
        GetComponent<SpriteRenderer> ().sprite = sArray [symbolType];
    }

    // Update is called once per frame
    void Update () {

    }
} 

So, my symbols move but after the lowest symbol goes up again, gap between symbols is not the same.

If anyone have experience in making slot machines, please share it with me. Thanks and have a nice day

Answer 1

Your problem is here :

if (symbol.transform.position.y <= -3.0f) 
{
    float newY = ((symbols.Count - 1) * symbolHeight) + transform.position.y;
    symbol.transform.position = new Vector3 (transform.position.x, symbols.Count*symbolHeight, transform.position.z);
}

You're checking if the symbol past the checking point so let's assume it's transform.position.y is equal to -3.1f and then you're trying to reset it on top by adding 3.0f ( symbolHeight ) instead of the actual position change ( 3.1f ). That's only an example and of course the values can vary.

---

To fix this I would suggest doing something like :

if (symbol.transform.position.y <= -3.0f) 
{
    Vector3 currentPosition = symbol.transform.position;
    currentPosition.y = (currentPosition.y + 3.0f) + (symbols.Count - 1) * symbolHeight;
    symbol.transform.position = currentPosition;
}

Try this online