Randomized Object Placement (Unity C#)

A simple Unity Editor script that places prefabs randomly scattered within a box collider. Very useful to place vegetation, grass, rubble or other objects in your scene if you don’t want to do this by hand! The script actually places Prefabs rather then clones, so if the base prefab is edited all objects are edited. The script isn’t perfect but it can be altered to your hearts desire.

It uses a list of objects from which it randomly chooses, so you can place multiple types/objects at once!

The script consists of 2 scripts, one to be placed on a GameObject in your scene, and the other is the Editor code which MUST BE PLACED INSIDE A FOLDER CALLED “EDITOR” IN YOUR UNITY PROJECT. Other wise the code will not work.

We made the script live on stream:

If you want to know more about how it works watch this video:

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Or just download the files and mess around with it!

SpawnObjectsInBounds.CS

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;

/****************************************************************************

Author: Cherry Nugget Games - Lex vd Berg
Free to use and adapt as you see fit! Have fun with it. It's not perfect.

*/

public class SpawnObjectsInBounds : MonoBehaviour
{
    [Header("Prefabs to Spawn")]
    [SerializeField] private List<GameObject> prefabs;

    //List of the spawned prefabs so they can be deleted. You CAN do this manual as well
    [SerializeField, HideInInspector] private List<GameObject> spawnedPrefabs;


    [Header("Settings")]
    [SerializeField] private BoxCollider boxCollider;
    private Bounds bounds;
    [SerializeField] private int density = 5; //The number of objects to spawn

    //Used to randomize rotation
    [SerializeField] private bool randomRotationX = true;
    [SerializeField] private bool randomRotationY = true;
    [SerializeField] private bool randomRotationZ = true;
    [SerializeField] private float randomRotationFactor = 360f;

    //Used to randomize scale
    [SerializeField] private bool randomScale = true;
    [SerializeField] private float randomScaleMin = 0.1f;
    [SerializeField] private float randomScaleMax = 1.5f;
   

    //SpawnObject should only be called in the Editor
    public void SpawnObjects()
    {
        if(boxCollider == null)
            boxCollider = GetComponent<BoxCollider>();

        bounds = boxCollider.bounds;
        boxCollider.isTrigger = true;

        for(int i = 0; i < density; i++)
        {
            //Using PrefabUtility.InstantiatePrefab actually spawns a prefab rather then a clone of the prefab object.
            GameObject obj = PrefabUtility.InstantiatePrefab(prefabs[UnityEngine.Random.Range(0, prefabs.Count)], transform) as GameObject; 

            obj.transform.rotation = Quaternion.Euler(randomRotationX ? UnityEngine.Random.rotation.x * randomRotationFactor : obj.transform.rotation.x, 
            randomRotationY ? UnityEngine.Random.rotation.y * randomRotationFactor : obj.transform.rotation.y, 
            randomRotationZ ? UnityEngine.Random.rotation.z * randomRotationFactor : obj.transform.rotation.z);
            
            float randomizedScale = UnityEngine.Random.Range(randomScaleMin, randomScaleMax);
            obj.transform.localScale = new Vector3(randomizedScale, randomizedScale, randomizedScale);

            //Set it to a random position on the bounds;
            obj.transform.position = RandomPointInBounds();

            spawnedPrefabs.Add(obj);
        }
    }

    public void ClearPrefabs()
    {
        //Destorys all the prefabs and clears the list of saved prefabs.
        //Called IN the editor script.
        foreach(GameObject child in spawnedPrefabs)
        {
            DestroyImmediate(child);
        }
       
        spawnedPrefabs.Clear();
    }

    private Vector3 RandomPointInBounds() 
    {
        //Returns a random point WITHIN the bounds
        return new Vector3(
            Random.Range(bounds.min.x, bounds.max.x),
            transform.position.y,
            Random.Range(bounds.min.z, bounds.max.z)
        );
    }
}

SpawnObjectsInBoundsEditor.CS

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor;

/****************************************************************************

Author: Cherry Nugget Games - Lex vd Berg
Free to use and adapt as you see fit! Have fun with it. It's not perfect.

NOTE: THIS SCRIPT MUST BE PLACED INSIDE A FOLDER CALLED “EDITOR” IN YOUR UNITY PROJECT. Other wise the code will not work.

*/

[CustomEditor(typeof(SpawnObjectsInBounds))]
public class SpawnObjectsInBoundsEditor : Editor
{
    public override void OnInspectorGUI()
    {
        base.OnInspectorGUI();

        SpawnObjectsInBounds soib = (SpawnObjectsInBounds)target;

        //Create two editor buttons to spawn and clear the objects
        if(GUILayout.Button("Spawn Objects"))
        {
            soib.SpawnObjects();
        }

        if(GUILayout.Button("Clear Objects"))
        {
            soib.ClearPrefabs();
        }
    }
}