Roll-A-Ball Tutorial Questions

"I would like them to produce some force on impact to move the ball in another direction"

Detection of Impact can be done using the OnTriggerEnter or OnCollisionEnter methods.

Applying force to a rigidbody is as simple as:

     private void OnCollisionEnter(Collision collision)
     {
       Rigidbody body = collision.collider.GetComponent<Rigidbody>();
       if (body != null)
       {
         body.AddForce(new Vector3(0, 1, 0));
       }
     }

You may want to think about ForceMode: This is the type of force that is put on the rigidbody. It changes what goes on behind the scenes in the physics engine. Like ForceMode.Acceleration ignores the mass of the rigidbody and applies the same acceleration to an object regardless of how heavy it is. ForceMode.VelocityChange is pretty much what it says, it will override current momentum and make the object sharply move in another direction. (This could be useful if you know the exact direction/position you want the ball to bounce to). The code below should make anything colliding with it move towards another target, however there could be caveats where the other object is being told to clip or move through this object.

       public Transform target;
       public float bounceSpeed = 10;

       private void OnCollisionEnter(Collision collision)
       {
         Rigidbody body = collision.collider.GetComponent<Rigidbody>();
         
         if (body != null)
         {
           Vector3 direction = (target.position - collision.transform.position).normalized;
           body.AddForce(direction * bounceSpeed, ForceMode.VelocityChange);
         }

       }

"Randomly distribute a fixed number of the objects, in different sizes and different shapes around the game environment."

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I'm assuming this is for some type of level creation? and not placement of pickups. Also, I'm not sure if you mean 'around' as in scattered throughout the level, or literally around, as in at the border of the level and not inside, I'm going with scattered within the level. There is a paragraph at the end commenting of random distribution of pick-ups.

Assuming that we have an empty scene with just a plane/quad/floor mesh. We can get the bounds of the area that we want to populate items inside.

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

     public class WorldGenerator : MonoBehaviour
     {
       public List<GameObject> prefabShapes;

       public Collider floor;

       private Bounds floorBounds;

       public string seed;
       [Range(1,10000)]
       public int maxObjects;
       [Range(0.5f, 10)]
       public float minScale;
       [Range(0.5f, 10)]
       public float maxScale;

       [Range(0,360)]
       public float minRotation;
       [Range(0, 360)]
       public float maxRotation;

       void Start () {
         floorBounds = floor.bounds;

         GenerateEnvironment();
       }
 
       void GenerateEnvironment()
       {
         Random.InitState(seed.GetHashCode());

         for (int i = 0; i < maxObjects; i++)
         {
           GetRandomAsset();
         }
       }

       private GameObject GetRandomAsset()
       {
         int selectedIndex = Random.Range(0, prefabShapes.Count);
         Vector3 forwardDirection = GetRandomRotation();
         Vector3 randomScale = GetRandomScale();
         Vector3 randomPosition = GetRandomPosition();

         GameObject newGO = GameObject.Instantiate(prefabShapes[selectedIndex], randomPosition, Quaternion.identity, transform);
         newGO.transform.LookAt(randomPosition + forwardDirection);
         newGO.transform.localScale = randomScale;

         return newGO;
       }

       private Vector3 GetRandomPosition()
       {
         float x = floorBounds.center.x + (floorBounds.extents.x * Random.Range(-1.0f, 1.0f));
         float y = floorBounds.center.y + (floorBounds.extents.y * Random.Range(-1.0f, 1.0f));
         float z = floorBounds.center.z + (floorBounds.extents.z * Random.Range(-1.0f, 1.0f));

         return new Vector3(x, y, z);
       }

       private Vector3 GetRandomRotation()
       {
         float x = Random.Range(minRotation, maxRotation);
         float y = Random.Range(minRotation, maxRotation);
         float z = Random.Range(minRotation, maxRotation);

         return new Vector3(x, y, z).normalized;
       }

       private Vector3 GetRandomScale()
       {
         float x = Random.Range(minScale, maxScale);
         float y = Random.Range(minScale, maxScale);
         float z = Random.Range(minScale, maxScale);

         return new Vector3(x,y,z);
       }
     }

Project Files

A random distribution can be very easy or fairly complicated depending on the requirements. A purely/very random straight-forward distribution/generation of content should be taken with caution (example: 'No Mans Sky') where you have no or little control over what the player will experience. It can create amazing experiences but probably only for 10% of the time and really boring or confusing experiences for the remainder. Pick-Ups affect the narrative of the game (e.g Health, Ammo, booby-trapped crate) depending on when the player finds them. A more complicated system would be to analyse what the player needs against the game difficulty and choose an appropriate item when the player gets within range of the Pick-Up, you could end up offering nothing at all if the player is doing really well. You could define Pick-up spawn points where they may be Helping the player or Enhancing the player. A helper may or may not have a pick up, where as an Enhancer will always have a pickup. you could also build on top of that what the future path of the player in the level is like (e.g Boss fight.)