Skip to main content
The Ultimate Multiplayer Inventory (UMI) system is a complete, production-ready item management framework for Unreal Engine 5+, designed by WarPath Studios.
UMI provides core systems for:
  • Inventory & storage
  • Equipment & character loadouts
  • Hotbar & quick actions
  • Loot generation
  • Crafting (optional integration)
  • World item interaction
  • Persistence & saving
UMI is built multiplayer-first, fully replicated, and optimized for authoritative server gameplay. Whether you’re building a survival game, MMO, RPG, extraction shooter, or sandbox project, UMI provides a reliable, extensible foundation.

​
Design Philosophy

  • Multiplayer First
    All operations follow strict server authority and validated RPCs.
  • Extensible Architecture
    Blueprint and C++ friendly with well-defined extension points.
  • Data-Driven
    Items, recipes, loot tables, and actions defined as Primary Data Assets.
  • Integration Ready
    Optional integrations with GAS, Enhanced Input, and Common UI.
  • Performance Focused
    Optimized replication, lightweight structs, async loading, and container-level networking.

​
Key Features (Summary)

​
Inventory

  • Flexible slot-based storage
  • Advanced stacking (durability, decay, provenance)
  • Weight & encumbrance support
  • Tag-based restrictions (per slot or container)
  • Auto-stack, auto-sort, item splitting, overflow handling
  • 8 sort types (name, rarity, quantity, category, value, etc.)

​
Equipment

  • Dynamic equipment slots
  • Mesh swaps (skeletal & static)
  • Body part hiding (hair, helmets, etc.)
  • Rarity-based visuals
  • Equipment presets (armor, jewelry, weapons, clothing)

​
Hotbar & Quick Actions

  • Quick slot system for weapons, tools, consumables
  • Auto-refill memory
  • Cooldowns per slot
  • Weapon swapping with equipment integration

​
Item Definition System

  • Data Asset–driven items
  • Display name, description, flavor text
  • Icons, meshes, multiple mesh variants (male/female/default)
  • Rarity tags
  • Durability & decay
  • Infusion/mod slots

​
Loot System

  • Weighted loot tables
  • Level/rank scaling
  • Quantity ranges
  • Single-use or respawnable containers
  • Easy integration with world actors

​
Crafting System

(Optional — only if Crafting plugin is installed)
  • SimpleQueue, MultiSlot, MaterialProcessing modes
  • Data Asset–driven recipes
  • Ingredient + tool + fuel requirements
  • Optional ingredients with bonus effects
  • Skill hooks for bonuses or perk effects
  • Pause/resume + progress tracking

​
Interaction System

  • Raycast and proximity-based interaction
  • Hold-interact with progress bar
  • Tool requirements
  • LOS checks, distance checks
  • Animation montage support
  • Foliage interaction

​
Persistence & Saving

  • Automatic save with configurable autosave
  • ISaveable interface
  • Bucket-based organization
  • Level streaming support
  • Async load
  • Extendable backend (file, cloud, DB)
  • All other UM plugins work automatically with this system.

​
Primary Action System

  • Central action dispatcher for item use
  • GAS integration for abilities/effects
  • Press/hold/release input modes
  • Global cooldowns and validation
  • Combo chains for melee

​
Player Profile

  • Central hub for all player systems
    (Inventory, equipment, hotbar, crafting, abilities, etc.)
  • Handles UI blocking
  • Handles teleportation & location management

​
Multiplayer

  • Full replication for all item operations
  • Server authority enforcement
  • Validated RPCs
  • Area-based networking for container replication
  • Bandwidth-optimized deltas

​
System Architecture (Summary)

​
Player Character

PlayerProfileComponent  (central hub)
InventoryComponent      (item storage)
HotbarComponent         (quick access)
EquipmentComponent      (equipped items)
InteractionComponent    (interaction logic)
AbilitySystemComponent  (optional GAS integration)

​
Crafting Stations

CraftingComponent
InventoryComponent (inputs)
InventoryComponent (outputs)

​
World Containers

InventoryComponent
SaveableContainerComponent

​
Data Asset Architecture

ItemDataAsset               (items)
ItemActionSet               (action behavior)
CraftingRecipeDataAsset     (recipes)
LootTable                   (loot)

​
Quick Start

  1. Enable UMI in your project
  2. Add InventoryComponent to player character
  3. Create ItemDataAssets
  4. Add InteractionComponent to your PlayerController
  5. Setup UI using the provided base widgets
  6. Test item pickup, equipment, and inventory management
For complete installation instructions, see Installation & Setup.

​
System Requirements

  • Unreal Engine 5.0+
  • Gameplay Ability System (optional, recommended)
  • Enhanced Input
  • Common UI
  • Multiplayer or single-player supported
  • All platforms supported by UE

​
Performance Considerations

  • Per-frame save budget
  • Delta replication for item changes
  • Area-of-interest networking
  • Async load operations
  • Optional object pooling for world items