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Item Pools

Author(s): benevolusgoat
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Crash course table of contents

The crash course is still a work in progress!

  1. Creating a mod.
    1. Creating the mod.
    2. Uploading a mod.
  2. Creating a passive item.
  3. Creating an active item.
  4. Adding to item pools.
  5. Making costumes.
  6. Making a new character.
  7. Creating entities.
    1. Creating effects.
    2. Creating enemies.
    3. Creating a familiar.
    4. Creating a projectile variant.
    5. Creating a tear variant.
  8. Adding sounds.
  9. Adding music.
  10. Making pocket items.
    1. Creating custom pills.
    2. Creating custom cards.
    3. Creating custom runes.
    4. Creating custom objects.
  11. Creating challenges.
  12. Creating new curses.
  13. Structuring your mod.
  14. Conclusion.

Item Pools are the primary method of finding and obtaining your custom collectibles within a run.

Video tutorial⚓︎

(This tutorial covers both Item Pools and Active Items) Active Items and Item Pools | Youtube Tutorial

itempools.xml⚓︎

Once you have items defined in an items.xml file within your mod's content folder, you will need to create an itempools.xml file in the same folder in order to add your collectibles into various item pools.

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<ItemPools>
    <Pool Name="treasure">
        <Item Name="My Item" Weight="1" DecreaseBy="1" RemoveOn="0.1"/>
    </Pool>
</ItemPools>

For every XML file, there is a "root tag" that goes from the start of the file to the end of the file, and multiple "child tags" that act as the individual entries. In this instance, itempools.xml entries will start with <ItemPools> and end with </ItemPools>. Individual item pool entries start and end with the Pool tag, and collectibles within those pools use the Item tag. Below are explanations of each variable contained within each of these tags.

The ItemPools tag does not contain any variables.

The Pool tag only requires one variable: Name. It is used to define the item pool the items will be added to.

Item tag variables
Variable Name Possible Values Description
Id int (Optional)
The id of the item in the itempool
When using this variable, you can't use the "name" variable.
Name String (Optional, recommended) The name of the item in the itempool.
When using this variable, you can't use the "id" variable.
Weight float Relative "likelyhood" that this item can be drawn from the pool. Default is 1. If this value reaches the "RemoveOn" value, the item will no longer be drawn from the pool.
DecreaseBy float Value on how often the item can be drawn from the pool. Default is 1
Everytime an item is drawn from the pool, this value is substracted from its Weight. This makes the item appear less likely on reroll until the weight reaches the RemoveOn value.
RemoveOn float If the Weight value reaches this, the item is no longer able to be drawn from the pool. Default is 0.1.

Available pools⚓︎

There is a pre-defined list of item pools you can add your items to. You cannot define your own custom item pools without the use of REPENTOGON. Below is the list of item pool names you can define to add your items to:

Item pool names
Variable Name Description
treasure Treasure Room Pool for Normal/Hard Mode
shop Shop Pool for Normal/Hard Mode
boss Boss Room Pool for Normal/Hard Mode
devil Devil Deal Pool for Normal/Hard Mode
angel Angel Room Pool for Normal/Hard Mode
secret Secret Room Pool for Normal/Hard Mode
library Library Pool for Normal/Hard Mode
shellGame Exclusive Bag of Crafting Item Pool for all modes
goldenChest Golden Chest Pool for all modes
redChest Red Chest Pool for all modes
beggar Beggar Pool for all modes
demonBeggar Devil Beggar Pool for all modes
curse Curse Room Pool for Normal/Hard Mode
keyMaster Key Master Pool for all modes
batteryBum Battery Bum Pool for all modes
momsChest Mom's Chest Pool for the unique chest located in Home
greedTreasure Treasure Room Pool for Greed/Greedier Mode
greedBoss Boss Room Pool for Greed/Greedier Mode
greedShop Shop Pool for Greed/Greedier Mode
greedCurse Curse Room Pool for Greed/Greedier Mode
greedDevil Devil Deal Pool for Greed/Greedier Mode
greedAngel Angel Room Pool for Greed/Greedier Mode
greedSecret Secret Room Pool for Greed/Greedier Mode
craneGame Crane Game Pool for all modes
ultraSecret Ultra Secret Room Pool for Normal/Hard Mode
bombBum Bomb Bum Pool for all modes
planetarium Planetarium Pool for Normal/Hard Mode
oldChest Old Chest Pool for the chest spawned by the Isaac's Tomb collectible
babyShop Baby Shop Pool for shop items while holding the Adoption Papers trinket
woodenChest Wooden Chest Pool for all modes
rottenBeggar Rotten Beggar Pool for all modes

Custom Item Pools⚓︎

With REPENTOGON, you can insert any Name you wish to register a new item pool. You can list your items as per usual, and can use Id instead of Name for item entries in order to add vanilla items to your custom pool.

You can fetch the unique ID of your item pool with Lua using Isaac.GetItemPoolIdByName. From there, you can treat it like you would any other item pool ID for fetching collectibles.