Object Pooling implementation ( reusing ) in Unity runner game

Question

I have my first runner game. Everything works fine. So, this question is about optimisation.

In my game, There are 15 platforms(road prefabs on which player runs). Randomly out 15 any 1 is instantiated and this keeps happening. When player passes a few platforms, The left behind platforms gets destroyed. I made a list to keep track of platforms and delete them last platform prefab ( list[0]). And new ones are instantiated ahead.

As the game approaches, It gets fast which means the operation of instantiating/destroying is happening more frequently now.

I read about object pooling. I understood the concept and I hold very strong opinion that I should use this in my game. I create an object pool. Works fine. Now my problem -

PROBLEM - How should I reuse object from my created pool? In my game, What I came up with is - The platforms that user has left behind should change position from back to forward( direction in which user is heading ). How can I achieve that ?

I followed these tutorials - https://www.youtube.com/playlist?list=PLLH3mUGkfFCXps_IYvtPcE9vcvqmGMpRK

Have a container with all (off-screen) platforms (e.g.: a `List`) and just pick the first available one and modify the position — UnholySheep, May 16 '17 at 19:47
@UnholySheep - I want my game to be unpredictable. I mean I want to use platforms randomly. — Vineet, May 16 '17 at 19:50
Then pick a random platform from that container - that's not really that much more code — UnholySheep, May 16 '17 at 19:52
If you have 15 different prefabs...well, you should have a pool for each one then, and randomly choose a pool to spawn from. — Serlite, May 16 '17 at 19:52
@Serlite - I thought of doing that as well, Then I was wondering - What if I'm creating another problem in order to solve one. — Vineet, May 16 '17 at 19:55
@UnHolySheep - I have problem with repositioning platforms. I'm a beginner. — Vineet, May 16 '17 at 19:56

score 2 · Accepted Answer · edited May 23 '17 at 12:10

When player passes a few platforms, The left behind platforms gets destroyed. I made a list to keep track of platforms and delete them last platform prefab ( list[0]). And new ones are instantiated ahead.

There many ways to make Object pooling. One of them includes adding the Objects to a queue and removing them when they are in use. When you want to recycle/destroy them, add them back to the List instead.

How should I reuse object from my created pool?

It's really easy. Instead of doing this each time:

Instantiate(prefab, postion, Quaternion.identity);

Do it many times when the game begins in the Start function and store then in an Array/List:

List<GameObject> pool = new List<GameObject>();

void Start()
{
    for (int i = 0; i < 50; i++)
    {
        GameObject tempObj = Instantiate(prefab, postion, Quaternion.identity) as GameObject;
        pool.Add(tempObj);
    }
}

When you need to instantiate Object during gameplay, just get one from the List/Array:

//Check if object is available in pool
if (pool.Count > 0)
{
    //Object is. Return 1
    GameObject objFromPool = pool[0];
    //Enable the Object
    objFromPool.SetActive(true);
}
else
{
    //Object is NOT. Instantiate new one
    GameObject objFromPool = Instantiate(prefab, postion, Quaternion.identity) as GameObject;
    //Enable the Object
    objFromPool.SetActive(true);
}

When you are done using the Object. Instead of doing Destroy(objFromPool);, reset the position of that GameObject, maybe disable it also if you want then add it back to the List:

//Reset Pos
objFromPool.transform.position = Vector3.zero;
//Disable?
objFromPool.SetActive(false);
//Return back to the array
pool.Add(objFromPool);

Finally, the best way of doing this is to instantiate all the objects into an array or list. Use an integer that you increment. The integer starts from 0 and increments until it reaches list/array.Length-1. You can then use that integer to get an Object from the pool.

You can see example of this method implemented as ArrayObjectPooling here and how to use it.

Thank You programmer. That waS What I needed ! – Vineet May 20 '17 at 08:10 — Vineet, May 20 '17 at 08:10

Object Pooling implementation ( reusing ) in Unity runner game

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