Inventory equipment

Inventory & Equipment

Build the inventory/equipment layer of a game — data model, gear generation, crafting, enhancement, UI, equipment, and (for online games) dupe-safe networked persistence. The skill spans three traditions and tells you which patterns are shared and which are mode-specific:

• Gacha / live-service (Genshin via the Grasscutter GameItem schema + leaked-server RNG RE — the best public source on a AAA loot generator).
• ARPG / looter (Diablo II/III/IV, Path of Exile 1/2, Last Epoch, Grim Dawn, Borderlands — affix systems, the deterministic↔random crafting dial).
• Online / MMO (WoW, EVE, Albion, Lost Ark — server-authoritative ownership and the duplication-prevention playbook).

The architecture rule

One item model, two families: instances carry state, materials carry counts — and every protection is a model invariant, not a UI rule. In online games, add a third: the server owns item state; the client sends intent, never state.

definition (static table)  type, rarity, stack limit, equip type, curves
instance (equipment)       stable GUID + level/exp/lock/rolled-affix state
count (materials)          itemId + count, clamped to stackLimit
tabs                       ItemType -> polymorphic tab (lists vs id->stack maps)
the invariant example      isDestroyable() = !locked && !equipped

Reference map

File	Covers
data-model.md	Instance/count split, stable GUIDs, polymorphic tabs, caps as policy (warehouse vs scarcity), the BotW counterpoint, definition-vs-instance, persistence integration
gear-generation.md	The Genshin 4-draw RNG pipeline (weighted pools, roll tiers, affix-ID encoding), ARPG affix systems (prefix/suffix, ilvl-gated tiers, weights, mutual exclusion), the deterministic↔random crafting spectrum (PoE orbs, D4 tempering/masterworking, LE forging potential, runewords, smart-loot), the constrained-guarantee funnel
enhancement.md	The unified enhancement service, per-type tables, 80% recycling, exp-overflow refunds, batch QoL, dissolve/salvage loops, recycle-into-value
inventory-ui.md	Layouts (grid/list/Tetris-weight), loot-filter DSLs (PoE/Last Epoch), search syntax (DIM), stable sorts + filters + lock plans, compare tooltips, loadouts/transmog/wardrobe, controller vs mouse, mass-salvage safety
networking.md	Server-authoritative ownership, the duplication root-cause catalog with real incidents, 2-phase-commit trades + escrow + row locks + idempotency, append-only ledgers / event sourcing, reconciliation, anti-cheat, sharding/account-stash consistency
pitfalls.md	16 failure modes (symptom → cause → prevention) with real incidents (D4 trade dupe, D3 integer-overflow gold dupe, D2 SoJ economy), debugging order, ship checklist

Build order (4 shippable tiers)

Tier 1 — Model and tabs
- [ ] Definition/instance/count split; stable GUIDs (never engine object IDs)
- [ ] Polymorphic tabs with per-tab caps; the new-item flag
- [ ] The lock invariant (isDestroyable = !locked && !equipped)
- [ ] Online: server-authoritative mutation path; client sends intent only
Tier 2 — Generation and enhancement
- [ ] Generation as weighted data tables (gacha 4-draw, or ARPG affix pools
      with ilvl gating); affix-ID encoding (stat+tier per ID)
- [ ] The crafting layer placed on the determinism dial (chosen deliberately)
- [ ] Unified enhancement service: per-type tables, recycling, batch with
      locked-excluded + high-value confirmation
Tier 3 — UI
- [ ] Virtualized grid/list + detail panel; async icons with placeholders
- [ ] Stable sort with instance-ID tiebreakers; filter + lock-plan rule engine
- [ ] Loot filter (drop-time) if acquisition outpaces curation
- [ ] Equip flows + compare panel (full before/after stats); mass-salvage
      gated by favorite/lock
Tier 4 — Equipment depth & online
- [ ] Set counting: equipped-only, per-character; bonuses as data affixes
- [ ] Loadouts: pin-by-instance vs clone-by-rule (choose + document fallback)
- [ ] Trade: 2-phase commit + escrow + row locks + idempotency + hash-chained
      log; soulbound gating on the most valuable items
- [ ] Persistence: ACID over an append-only ledger; reconciliation job

Key numbers (starting points — sourced anchors)

Parameter	Value	Anchor
Genshin main-stat pools	sands 1334/1333/1333/500/500 weights; substat weights flat 6 / %·EM·ER 4 / crit 3	leaked server datamine
Genshin roll tiers	4 equiprobable: 70/80/90/100% of max; upgrade every +4	datamine
PoE rare mod cap	3 prefix + 3 suffix = 6; T1–T2 need ilvl ~82–86	poewiki
D2 gamble odds	Unique 0.05% / Set 0.10% / Rare 10% / Magic ~89.85%; ilvl clvl−5..+4	Arreat Summit
D3 smart loot	~85% class-tailored / ~15% random	D3 2.0.1 notes
D4 (post-2.5)	4 base affixes; tempering deterministic pick; masterwork max Quality 20	Blizzard 2.5.0
Last Epoch	forging potential ~20–40 (rare→exalted); craftable cap T5	community
Enhancement	5★ +20 = 270,475 EXP; fodder recycling = base + 80% invested	Genshin wiki
BotW pouches	weapons 8→19(+1), bows 5→13(+1), shields 4→20 (slot caps AS progression)	wiki

Full sourced tables (with flagged "do-not-invent" gaps) live in each reference file.

Engine mapping (summary)

Generic block	Unity 6	UE5 (5.4+) — Lyra is the first-party reference
Model	SO definitions + serializable instances linked by custom GUID (never GetInstanceID())	ItemDefinition (const) + ItemInstance (runtime) + ItemFragments (composition)
Equipment stats	hand-rolled recompute pipeline	equip = infinite GameplayEffect (handle-guaranteed removal); set bonuses via tag-count
Replication	Mirror/NGO ownership	registered subobject lists + FFastArraySerializer (order NOT guaranteed → stable UI sorts)
UI grid	UITK ListView virtualization (no native GridView → rows-of-cells)	UMG ListView/TileView (pooled); CommonUI for controller nav
Backend	UGS Cloud Code rolls + Economy writes (deny client Write)	custom/PlayFab v2 (per-instance StackId, IdempotencyId)

Full detail in networking.md and the reference files.