Procedural Item Generation
For ProcGene, I want to create a way to have procedurally generated items.
I found two games which had item generation systems which would fit really well into ProcGene; Path of Exile and Borderlands.
In this document I will be taking a look at what properties the items have, and how the systems generate the items.
Borderlands
Borderlands is a First Person Shooter RPG, which also has a focus on Loot Grinding.
Borderlands has a few different items, but I will only take a look at how the Guns and Shields are generated, since I think that’s where Borderlands really shines, and that’s the only part that I really want to implement in ProcGene.
Guns
Guns in Borderlands have quite a lot of properties, so I will be splitting them into the gun overall properties and the gun parts.
Gun Properties
| Property | Explanation |
|---|---|
| Weapon Type | Determines what kind of gun this item is |
| Manufacturer | The company that manufactures this gun, has different strengths and weaknesses |
| Weapon Grade | Specifies what version of a gun this is |
| Rarity | Used to show what the overall value of the gun parts are |
| Damage | How much damage it deals per hit |
| Accuracy | How likely it is to hit where you’re aiming at |
| Fire Rate | How often the gun can shoot per second |
| Reload Speed | How quickly the gun can be reloaded |
| Magazine Size | How many bullets you can fire before you need to reload |
| Recoil | How much the gun recoils when you fire a shot |
| Level Requirement | What level the player must be before it can use this gun |
Gun Parts
| Property | Explanation |
|---|---|
| Material | What metal the gun is made of |
| Body | The body of the gun |
| Barrel | Influence the damage and the accuracy |
| Magazine | Determines the amount of ammo |
| Accessory | Alter the performance of the gun in various ways. Can change the stats, or add elemental effects |
| Sight | Determines the amount of zoom when looking down the barrel |
| Stock | Affects the recoil and reload speed |
| Grip | The grip of the gun |
| Level | Restricts the amount of damage the gun can do, and the Level Requirement |
Generation
The generator starts with deciding on the Weapon Type, Manufacturer and Weapon Grade.
After these are selected, the game will construct the gun by selecting the Material, and all Gun Parts.
The gun must now be named.
The first part of a weapon’s name is its Prefix. Each manufacturer has a list of Prefixes, and which one a weapon gets is determined by a number of factors including Parts, what Element it has (if any) and any bonuses the weapon has. Prefixes form a hierarchy, with each having a set priority. The highest-priority Prefix is the one that will be displayed, while all others will be hidden.
The second part of a weapon’s name is its Title. The Title is determined entirely by the combination of Body and Barrel parts it has; the Body is determined by the weapon’s Manufacturer, while the Barrel assigns a specific Title from that Manufacturer’s list.
It’ll finally end up with a gun like this;
Path of Exile
Path of Exile is an online Isometric Action RPG, with a focus on Loot Grinding. It is heavily inspired by Diablo II.
Path of Exile has a lot of different items which all have their own properties. I’m only going to look at Weapons and Armour, since this is what I am trying to implemented in ProcGene.
Weapons
Weapons in Path of Exile have the following properties;
| Property | Explanation |
|---|---|
| Weapon Type | Determines what Weapon this item is (Bow, Axe, etc) |
| Hands Needed | If the weapon is one or two handed |
| Quality | Increases Physical Damage |
| Physical Damage | How much Physical Damage is dealt per hit |
| Elemental Damage | How much Elemental Damage is dealt per hit |
| Critical Strike Chance | How often the Weapon performs a Critical Strike, which increases damage |
| Attacks Per Second | How many times the weapon can attack per second |
| Weapon Range | How far the weapon can reach |
| Requirements | What attributes the player needs to meet before it can wear this armour piece |
Armour
Armour has the following properties;
| Property | Explanation |
|---|---|
| Armour Type | Determines what Armour piece this item is |
| Quality | Increases Armour Rating, Evasion Rating and Energy Shield |
| Armour Rating | Reduces incoming damage |
| Evasion Rating | Increases chance to dodge attacks |
| Energy Shield | Extra health pool on top of Life, which automatically regenerates after not getting hit for some time |
| Requirements | What attributes the player needs to meet before it can wear this weapon |
Modifiers
Path of Exile spices up the item generation by adding Modifiers. A Modifier applies stats, a buff or grants a skill to the item.
These go from simple modifiers like + # to Strength, to interesting modifiers like Adds # to # Cold Damage to Attacks with this Weapon per 10 Dexterity.
There are 3 types of modifiers;
| Type | Usage |
|---|---|
| Prefix | Used to identify the modifier on the item |
| Suffix | Used to identify the modifier on the item |
| Implicit | Extra modifier, doesn’t count towards Max. Modifier count |
A Modifier has the following properties;
| Property Name | Explanation |
|---|---|
| Name | What the Modifier is called |
| Domain | What Item this modifier can be applied to |
| Type | Whether the modifier is a Prefix, Suffix or Implicit, |
| Level | The required level the Item Level needs to be so it can acquire this Modifier |
| Mod Group | Groups for modifiers based on what changes they apply, every group can only be applied once to any Item |
| Tier | The ranking of this mod in its' Mod Group |
All items also have two other properties which play a big part for Modifiers;
Rarity
Items can be one of these 4 rarities, which grant # of modifiers;
| Rarity | Max. Modifiers | Prefixes | Suffixes |
|---|---|---|---|
| Common | 0 | 0 | 0 |
| Magic | 2 | 1 | 1 |
| Rare | 6 | 3 | 3 |
| Unique | No set limit | - | - |
Item Level
Item Level determines what tier of a modifier the item gets. The higher the Item Level, the better the Modifier can be.
Generation
The Rarity is rolled first. This will return either Common, Magic, Rare or Unique.
A Base Item is chosen based on the Item Level, and after that the Item Type is decided, based on what the Base Item is.
The Modifiers are then picked, based on the Rarity, Item Level, Base Item and Item Type.
The name is then decided. If the Rarity is Magic, the name is done like so {Prefix Name} Base Item Name {Suffix Name}.
If the Rarity is Rare, the name is selected by using the Rare Item Name Index, in which two random words are chosen from a pool and are combined into the name. These names aren’t influenced by what kind of Item Type they have.
After all these steps, the generator would have made something like this;
Sources
Beginner’s Guide to Borderlands Weapon Generator | Gearbox Forum
Part Spotters Guides - Borderlands 2 / Loot and Weapons | Gearbox Forum
Weapons | Borderlands Fandom
Borderlands 2 Weapons | Borderlands Random
Modifiers | Official Path of Exile Wiki
Rare Item Name Index | Official Path of Exile Wiki
