Spawn GameObjects Randomly Within Bounds in Unity (Part 5)

Let’s see how we can randomly spawn GameObjects within a confined boundary.

Step 1: Set up the scene

Start by either creating a new Unity 3D project or opening an existing scene. Ensure it includes a “Main Camera” and a directional light. We’ll build upon the scene from the How to destroy an enemy GameObject on collision in Unity Answer.

Step 2: Enemy creation

To create enemies, use the cube primitive GameObject and attach a collider to it.

Note: If you are following the series, you can use the previously created one in the How to destroy an enemy GameObject on collision in Unity Answer.

Step 3: Create a script

To represent the spawn area in which we want to spawn enemies at random intervals, create a confined boundary using a combination of Vector3 values. Instead of using a collider, we can set up a range of minimum and maximum values for the X, Y, and Z coordinates. Randomly generate spawn positions within these ranges.

Let’s create the GameObjectSpawner script, which will randomly create a specified number of objects within a confined boundary. The spawning is controlled by the range of possible object counts and random time delays between spawns, allowing for dynamic and varied gameplay experiences.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class GameObjectSpawner : MonoBehaviour
{
    public GameObject objectPrefab;
    public int minObjectsToSpawn = 5;
    public int maxObjectsToSpawn = 10;
    public float minSpawnDelay = 1f;
    public float maxSpawnDelay = 2f;
    public float fixedSpawnHeight = 2f; // Fixed Y-axis spawn position
    public float minXPosition = -5f;
    public float maxXPosition = 5f;
    public float minZPosition = -5f;
    public float maxZPosition = 5f;
    void Start()
    {
        StartCoroutine(SpawnObjectsWithDelay());
    }
    IEnumerator SpawnObjectsWithDelay()
    {
        int numObjectsToSpawn = Random.Range(minObjectsToSpawn, maxObjectsToSpawn + 1);
        for (int i = 0; i < numObjectsToSpawn; i++)
        {
            Vector3 spawnPosition = GetRandomSpawnPosition();
            Instantiate(objectPrefab, spawnPosition, Quaternion.identity);
            float randomDelay = Random.Range(minSpawnDelay, maxSpawnDelay);
            yield return new WaitForSeconds(randomDelay);
        }
    }
    Vector3 GetRandomSpawnPosition()
    {
        float randomX = Random.Range(minXPosition, maxXPosition);
        float randomZ = Random.Range(minZPosition, maxZPosition);
        return new Vector3(randomX, fixedSpawnHeight, randomZ);
    }
}

Lines 24–36: The SpawnObjectsWithDelay coroutine is responsible for spawning objects. It generates a random number between minObjectsToSpawn and maxObjectsToSpawn to determine how many objects to spawn.

Inside the for loop, it calls the GetRandomSpawnPosition method to get a random position within the specified boundary. It then instantiates objectPrefab at spawnPosition with no rotation (Quaternion.identity).
After spawning each object, it introduces a random delay between minSpawnDelay and maxSpawnDelay using Random.Range and yield return new WaitForSeconds.

Lines 38–43: The GetRandomSpawnPosition method generates a random position within the specified X and Z boundaries (minXPosition, maxXPosition, minZPosition, maxZPosition) while keeping the Y-axis position fixed at fixedSpawnHeight.

Step 4: Attach the script

Attach the script to an empty GameObject or a dedicated spawner GameObject in the scene. Set the parameters for the minimum and maximum number of GameObjects to spawn as well as the boundaries of the spawn area (e.g. minX, maxX, minY, maxY, minZ, maxZ).

Either attach the script to the plane GameObject if we only want enemies to spawn on the plane, or create another empty GameObject and add GameObjectSpawner as a component to it. In this case, we will attach the script to the plane GameObject.