Building System

Canonical GDD content

Free-form (Rust-like) construction — [CONFIRMED]. Players place modular structural pieces that snap together to form custom bases. Bases are persistent on the server and raidable by other players.

Build modes

1. Structure mode: place structural pieces (foundation, wall, floor, ceiling, doorway, stairs, ramp, window). Pieces snap to sockets on adjacent pieces; foundations snap to valid terrain.
2. Deployable mode: place functional objects (door, storage box, crafting station, campfire/stove, sleeping bag/bed, workbench, turret [TBD], traps). The workbench is both a crafting station and the firearm customization station (09-Weapon-Customization.md); anyone nearby can use firearm work on it.

A build component (UBuildComponent) shows a ghost/preview, validates placement (collision, snap, support, ownership rules), and sends a server request to commit.

Piece set (v1 — minimal)

Expand the set in later phases (high walls, gates, foundation steps, triangle pieces). Keep v1 small to control art + netcode + raiding-balance cost.

Snapping & placement rules

• Socket-based snapping (each piece exposes snap sockets); free rotation when not snapped.
• Placement validation (server-authoritative): no overlap with disallowed geometry, must be supported, must be within a build-allowed area, and the placer must have build permission for that location.
• Build privilege: a Tool Cupboard / Territory Anchor concept [RECOMMENDATION] — placing an anchor claims a radius where only authorized players (squad/clan) can build/modify. This is the standard solution to grief-proofing free-form building and ties into territory progression. See ../04-Multiplayer/03-Clans-and-Squads.md.

Materials & upgrade tiers

Pieces are crafted from gathered resources and can be upgraded in tiers (e.g., Twig → Wood → Stone → Metal → Armored). Higher tiers have more HP and resist more raid damage. Tier list and HP values are [TBD].

Health, damage & raiding

• Every placed piece has HP and a material tier; raid tools (explosives, melee against soft sides, cutting tools) deal type-specific damage. See ../04-Multiplayer/04-PvP-Raiding-and-Trading.md.
• [CONFIRMED] full raiding is allowed — bases can be breached and looted.
• [RECOMMENDATION] weak-side/strong-side mechanics (walls cheaper to break from the inside) for raid depth.
• Decay: unmaintained structures decay over time [RECOMMENDATION] to clean up abandoned bases on persistent servers (critical for server health).

Networking & persistence — [RISK]

This is one of the most expensive systems to do well:

• A base may contain hundreds of pieces. Naïvely each-piece-as-an-actor does not scale to ~40–60 players × many bases. Mitigations to evaluate: Instanced Static Meshes / Hierarchical ISM for visuals, lightweight per-piece state, dormancy, and net relevancy by distance. The project has ISM tooling available.
• All placed structures must be persisted and restored on server restart (positions, tiers, HP, ownership, container contents). See ../04-Multiplayer/01-Network-Architecture.md.
• Decide early: piece representation (actor vs ISM + data record), save schema, and relevancy strategy. [TBD] but must be solved in Phase 1 since everything else builds on it.

Implementation guidance

• UBuildComponent (C++) handles mode, preview, validation request.
• Building pieces defined data-driven (mesh, sockets, tier, HP, cost) so adding pieces is content work, not code.
• Preview/ghost and input handling are reasonable to drive partly in Blueprint; placement validation and commit must be C++ server logic.