How to Build a Professional Weighted Loot System in Unity

using System.Collections.Generic; using UnityEngine;  namespace EndlessEncounters {     /// <summary>     /// A ScriptableObject that defines a collection of items with weighted chances for dropping.     /// This allows designers to create and manage loot tables easily in the editor.     /// </summary>     [CreateAssetMenu(fileName = "NewLootTable", menuName = "Endless Encounters/Loot Table")]     public class LootTable : ScriptableObject     {         [System.Serializable]         public class LootItem         {             public string itemID;             [Min(0f)] public float weight;         }          public List<LootItem> lootItems = new List<LootItem>();         private float totalWeight;         private bool isInitialized = false;          private void Initialize()         {             if (isInitialized) return;             totalWeight = 0f;             foreach (var item in lootItems) { if (item.weight > 0) totalWeight += item.weight; }             isInitialized = true;         }          public string GetLoot()         {             Initialize();             if (totalWeight <= 0 || lootItems.Count == 0) return null;             float randomValue = Random.Range(0f, totalWeight);             foreach (var item in lootItems)             {                 if (item.weight <= 0) continue;                 if (randomValue <= item.weight) return item.itemID;                 randomValue -= item.weight;             }             return null;         }                  private void OnValidate() { isInitialized = false; }     } } 

Key Design Choices

• Weighted Logic: Instead of dealing with fragile percentages that must add up to 100, this system uses weights. An item with a weight of 50 will appear five times more often than an item with a weight of 10. It's intuitive and easy to balance.
• OnValidate for Designers: This script includes a special OnValidate function. This is a Unity Editor trick that automatically detects when a designer changes a weight value in the Inspector and tells the system to recalculate its totals. It makes the tool foolproof.
• Clean API: The simple GetLoot() method is all you need to call from your enemy death script or treasure chest script to get a valid item ID.

The Bigger Picture

This robust loot table system is just one of the core modules inside the Endless Encounters: Dynamic Mission & Loot Generator. The main engine uses these tables to automatically generate meaningful rewards for the infinite procedural quests it creates.

If you found this script helpful and want a complete engine that handles not just loot, but also dynamic mission generation, objective tracking, and XP scaling, please check out the full asset on our main page.