--- title: "Character Compositor API Specification" description: "Godot-side compositor data model and node architecture for runtime character compositing" type: spec status: active sprint: 28 ticket: 684 created: 2026-03-17 --- # Character Compositor API Specification **Produced by:** Sprint 28 Character Visuals Workshop (ticket #684) **Date:** 2026-03-17 **Implements:** D-149 (3D live rendering), D-150 (inverted hull outline), D-151 (direction count), D-152 (LOD strategy) **Upstream:** `docs/design/character-visuals-spec.md` **Downstream:** Ticket #693 (compositor implementation, client team) --- ## 1. Overview The `CharacterCompositor` is a `Node3D` subtree that replaces the current single `Sprite2D` in `EntityRenderer`. It manages all visual layers for a character: body, clothing, hair, face, accessories, and overlays. It exposes a clean API that `EntityRenderer` calls when appearance or state changes. The compositor is **purely presentational** — it never queries the server or simulation. All data flows from `EntityRenderer` downward. --- ## 2. Direction Enum ```gdscript enum CharacterFacing { NORTH, # Server facings: N, NW EAST, # Server facings: NE, E (source mesh — not mirrored) SOUTH, # Server facings: SE, S WEST, # Server facings: SW, W (mirror of EAST) } ``` **Perception vs. rendering — critical distinction:** - `CharacterFacing` (4 values) is the **rendering output** — what the compositor acts on. - The server tracks 8 facing directions for the **perception system** (fog-of-war, vision cone). The server's 8-direction value is never passed directly to the compositor. - `EntityRenderer` is responsible for mapping the server's 8-direction value to one of the 4 `CharacterFacing` values and passing that to `compositor.set_facing()`. - Diagonal facings (NE, NW, SE, SW) do not exist as compositor states. They are perception inputs only. - `ModelRoot` rotation uses the true 8-direction angle for body lean; `CharacterFacing` controls mesh/material group selection. **Server-to-client mapping** (exact snap logic — Tyre to confirm based on camera/grid orientation): | Server Facing | Client Visual Group | Notes | |---|---|---| | N | NORTH | | | NW | NORTH | | | NE | EAST | | | E | EAST | | | SE | SOUTH | | | S | SOUTH | | | SW | WEST | Mirror of EAST | | W | WEST | Mirror of EAST | The 3D model root rotates to the true server-facing angle (all 8). The visual group snap controls which mesh variant is loaded, but the root rotation gives subtle body lean within a group. --- ## 3. Color Override Data ```gdscript class_name CharacterColors extends Resource ## Skin @export var skin_primary: Color = Color("#c8a882") @export var skin_secondary: Color = Color.TRANSPARENT # TRANSPARENT = auto-derive from skin_primary ## Hair @export var hair_primary: Color = Color("#3a2a1a") @export var hair_highlight: Color = Color.TRANSPARENT # TRANSPARENT = auto-derive from hair_primary ## Clothing slot overrides — keyed by item_id ## Each item carries its own cloth_primary/secondary/accent ## This dict maps item_id -> ClothingColors @export var clothing: Dictionary = {} # item_id (int) -> ClothingColors ``` ```gdscript class_name ClothingColors extends Resource @export var cloth_primary: Color = Color.WHITE @export var cloth_secondary: Color = Color.TRANSPARENT # TRANSPARENT = use authored default @export var cloth_accent: Color = Color.TRANSPARENT # TRANSPARENT = use authored default ``` --- ## 4. Appearance Data ```gdscript class_name CharacterAppearance extends Resource ## Body @export var body_type: int = 1 # 0=slim, 1=average, 2=stocky @export var face_id: int = 0 # index into face mesh library @export var hair_id: int = 0 # index into hair mesh library ## Clothing — item IDs (0 = no item for that slot) @export var clothing_torso_id: int = 0 @export var clothing_legs_id: int = 0 @export var footwear_id: int = 0 @export var accessory_ids: Array[int] = [] # multiple accessories supported ## Overlays — IDs (empty = none) @export var scar_ids: Array[int] = [] @export var tattoo_ids: Array[int] = [] ## State @export var injury_state: int = 0 # 0=undamaged, 1=light, 2=heavy @export var expression_state: int = 0 # 0=neutral, 1=alert, 2=stressed, 3=distressed ## Colors @export var colors: CharacterColors = CharacterColors.new() ``` --- ## 5. Node Architecture ``` CharacterCompositor (Node3D) — root; receives API calls ├── ModelRoot (Node3D) — rotated to true server-facing angle │ ├── BodyMesh (MeshInstance3D) — body_type variant; skin regions │ ├── LegClothing (MeshInstance3D) — clothing_legs_id mesh; cloth regions │ ├── Footwear (MeshInstance3D) — footwear_id mesh; cloth regions │ ├── TorsoClothingBack (MeshInstance3D) — back half of torso clothing │ ├── TorsoClothingFront (MeshInstance3D) — front half of torso clothing │ ├── Accessories (Node3D) — child MeshInstance3D per accessory_id │ ├── HeadFace (MeshInstance3D) — face_id variant; skin + expression regions │ ├── HairBack (MeshInstance3D) — hair_id variant (back mesh) │ ├── HairFront (MeshInstance3D) — hair_id variant (front mesh) │ └── Overlays (Node3D) │ ├── ScarOverlay (MeshInstance3D) — scar_ids; additive blend │ ├── TattooOverlay (MeshInstance3D) — tattoo_ids; multiply blend │ ├── InjuryOverlay (MeshInstance3D) — injury_state; over clothing + skin │ └── ExpressionOverlay (MeshInstance3D) — expression_state; over face └── LOD (Node3D) — manages tier transitions └── BillboardSprite (Sprite3D) — tier 2 impostor (baked outline included) ``` **Outline:** Inverted hull is a material property on `ModelRoot` and all child meshes — not a separate node. Disabled at LOD Tier 2 (billboard replaces the entire ModelRoot). --- ## 6. Public API ```gdscript class_name CharacterCompositor extends Node3D ## Apply a full appearance update. ## Called on: character creation, equip/unequip, editor preview. func apply_appearance(appearance: CharacterAppearance) -> void: pass ## Update facing direction. Called every time server reports a facing change. func set_facing(facing: CharacterFacing) -> void: pass ## Set LOD tier. Called by the global LOD manager based on frame budget. ## 0 = full, 1 = simplified mesh, 2 = billboard impostor func set_lod_tier(tier: int) -> void: pass ## Return a snapshot of the current appearance (used by character editor). func get_appearance() -> CharacterAppearance: return CharacterAppearance.new() ## Update a single color region without a full appearance rebuild. ## More efficient than apply_appearance() for color picker preview. func set_color(region: StringName, color: Color) -> void: pass ``` --- ## 7. EntityRenderer Integration Current state: `EntityRenderer` (`client/scripts/rendering/entity_renderer.gd`) uses a single `Sprite2D` per entity. **Migration plan:** 1. Add `CharacterCompositor` as a packed scene resource 2. In `EntityRenderer._ready()`: if entity is a character type, instantiate `CharacterCompositor` and add as child; hide `Sprite2D` 3. Wire `EntityRenderer`'s existing facing-update path to call `compositor.set_facing()` 4. Wire `EntityRenderer`'s appearance-update path to call `compositor.apply_appearance()` 5. Register `EntityRenderer` with the global LOD manager to receive `set_lod_tier()` calls Non-character entities (items, furniture, tiles) continue to use `Sprite2D` and are unaffected. --- ## 8. LOD Manager A singleton (`CharacterLODManager`) monitors the GPU frame budget and calls `set_lod_tier()` on registered `CharacterCompositor` instances. **Interface:** ```gdscript class_name CharacterLODManager extends Node ## Register a compositor for LOD management. func register(compositor: CharacterCompositor, entity_id: int) -> void: pass ## Unregister when entity leaves scene. func unregister(entity_id: int) -> void: pass ## Called by compositor to report its distance from player (updated each frame by EntityRenderer). func update_distance(entity_id: int, distance: float) -> void: pass ``` **LOD algorithm — proactive, not reactive:** The LOD manager operates on **projected character count**, not frame-drop detection. Triggering on frame drop produces visible hitches. Proactive demotion is invisible to the player. ``` Each frame: projected_full_count = count of registered compositors within full-detail radius if projected_full_count > TIER_0_BUDGET: demote furthest tier-0 compositors until within budget if still over TIER_1_BUDGET: demote furthest tier-1 compositors to tier-2 until within budget When count drops below budget * HYSTERESIS_FACTOR: promote nearest tier-2 → tier-1, tier-1 → tier-0 When paused (get_tree().paused == true): promote all compositors to tier 0 ``` `TIER_0_BUDGET` and `TIER_1_BUDGET` are tunable constants. Initial values TBD by profiling. **Billboard impostor requirements (Tier 2):** The impostor sprite is not a generic silhouette — it is a per-character snapshot. The bake process **must** preserve: 1. **Body size tier** — slim / average / stocky silhouette must be distinguishable at billboard scale 2. **Dominant clothing color** — `cloth_primary` of the most visible clothing item must read clearly These are non-negotiable fidelity requirements. Implementation must not optimize them away. Implementation detail: use an indexed priority queue keyed by distance. Full implementation is Tyre's responsibility in ticket #693. --- ## 9. Character Editor Integration The character creation/editor screen (`character_select.gd` and related) can use `CharacterCompositor` directly for the preview pane. **Preview pane setup:** - Instantiate `CharacterCompositor` in a `SubViewport` - Apply `CharacterAppearance` from the current editor state on every change - Default facing on open: **`CharacterFacing.SOUTH`** — face-forward at 30° camera, maximum cosmetic utility - Button order: S → E → N → W - No LOD management in the editor — always tier 0 ```gdscript # In editor preview pane script: func _on_direction_button_pressed(facing: CharacterFacing) -> void: preview_compositor.set_facing(facing) func _on_appearance_changed() -> void: preview_compositor.apply_appearance(build_appearance_from_editor_state()) ``` **D-146 compatibility note:** D-146 specifies "tile-scale sprite with heavy zoom." Under D-149 (3D live rendering), the editor preview shows the live 3D compositor rendered in a SubViewport at tile scale, then displayed zoomed. This is compatible with D-146's intent (showing the actual in-game appearance, not a separate portrait render). D-146 is not superseded. --- ## 10. Asset Pipeline Notes **For Araminta (visual team):** - Each body type variant is a separate `.blend`/`.glb` export for `BodyMesh` - Clothing items export as separate `.glb` per body type (e.g. `jacket_01_slim.glb`, `jacket_01_average.glb`) - Hair styles export as two meshes per style: `hair_short_a_back.glb`, `hair_short_a_front.glb` - Color regions are defined via UV2 channel: compositor reads UV2 to apply `ShaderMaterial` color overrides per region - Naming convention for regions: UV2 islands correspond to named shader uniforms (`uniform sampler2D skin_primary_mask`, etc.) **For tickets #686–#692 (visual team):** - Reference this spec and the `CharacterAppearance` data class for mesh naming and region conventions - All meshes must validate at the 30° tilt, 45° map rotation camera (D-148) — no art review at top-down angle --- ## 11. Open Questions | Item | Status | Owner | |---|---|---| | Exact server-facing → visual group mapping | Open | Tyre — confirm against camera/grid orientation in compositor implementation | | Expression: mesh swap vs. morph target | Open | Tyre — cost/quality tradeoff | | Clothing mesh per body type vs. compositor-level scale | Open | Tyre — separate `.glb` per body type is simpler; scaling risks clipping | | UV2 region masking vs. vertex color for color regions | Open | Tyre — UV2 is cleaner; vertex color is cheaper; both work | | Impostor bake process for LOD Tier 2 | Open | Tyre — static pre-bake vs. runtime bake |