How can I make also the Y (Height) to be random ?

Unity Engine
1 
using System;
using UnityEngine;
using Random = UnityEngine.Random;

[ExecuteInEditMode]
public class SpawnObjects : MonoBehaviour
{
    // for tracking properties change
    private Vector3 _extents;
    private int _objectCount;
    private float _objectSize;

    public GameObject objectToSpawn;

    /// <summary>
    ///     How far to place spheres randomly.
    /// </summary>
    public Vector3 Extents;

    /// <summary>
    ///     How many spheres wanted.
    /// </summary>
    public int ObjectCount;

    public float ObjectSize;

    private void OnValidate()
    {
        // prevent wrong values to be entered
        Extents = new Vector3(Mathf.Max(0.0f, Extents.x), Mathf.Max(0.0f, Extents.y), Mathf.Max(0.0f, Extents.z));
        ObjectCount = Mathf.Max(0, ObjectCount);
        ObjectSize = Mathf.Max(0.0f, ObjectSize);
    }

    private void Reset()
    {
        Extents = new Vector3(250.0f, 20.0f, 250.0f);
        ObjectCount = 100;
        ObjectSize = 20.0f;
    }

    private void Update()
    {
        UpdateSpheres();
    }

    private void UpdateSpheres()
    {
        if (Extents == _extents && ObjectCount == _objectCount && Mathf.Approximately(ObjectSize, _objectSize))
            return;

        // cleanup
        var spheres = GameObject.FindGameObjectsWithTag("SpawnObject");
        foreach (var t in spheres)
        {
            if (Application.isEditor)
            {
                DestroyImmediate(t);
            }
            else
            {
                Destroy(t);
            }
        }

        var withTag = GameObject.FindWithTag("Terrain");
        if (withTag == null)
            throw new InvalidOperationException("Terrain not found");

        for (var i = 0; i < ObjectCount; i++)
        {
            var o = Instantiate(objectToSpawn);
            o.tag = "SpawnObject";
            o.transform.localScale = new Vector3(ObjectSize, ObjectSize, ObjectSize);

            // get random position
            var x = Random.Range(-Extents.x, Extents.x);
            var y = Random.Range(-Extents.y, Extents.y); //Extents.y; // sphere altitude relative to terrain below
            var z = Random.Range(-Extents.z, Extents.z);

            // now send a ray down terrain to adjust Y according terrain below
            var height = 10000.0f; // should be higher than highest terrain altitude
            var origin = new Vector3(x, height, z);
            var ray = new Ray(origin, Vector3.down);
            RaycastHit hit;
            var maxDistance = 20000.0f;
            var nameToLayer = LayerMask.NameToLayer("Terrain");
            var layerMask = 1 << nameToLayer;
            if (Physics.Raycast(ray, out hit, maxDistance, layerMask))
            {
                var distance = hit.distance;
                y = height - distance + y; // adjust
            }
            else
            {
                Debug.LogWarning("Terrain not hit, using default height !");
            }

            // place !
            o.transform.position = new Vector3(x, y, z);
        }

        _extents = Extents;
        _objectCount = ObjectCount;
        _objectSize = ObjectSize;
    }
}

I changed the line:

var y = Random.Range(-Extents.y, Extents.y); //Extents.y; // sphere altitude relative to terrain below

But what I’m getting is part of the objects above the terrain and some under the terrain:

1920×1080 240 KB

And I want the random height to be only above the terrain.
For example if I change the Extents Y value to 0 all objects will be on terrain ground if I change it to 100 all objects will be random heights from 0(ground) to 100 range.

2

I’m not sure I understand your issue. If you want them all to be above, then you need to set your range to be only values available above. So if that is 0 to extents.y, then set your random to use 0 and extents.y.

1 Like