# ADR 0018: Componentized actor inspector and materials

## Status

Accepted.

## Context

The actor inspector had started to expose too many unrelated concerns through a
single static mesh renderer entry: source model paths, mesh labels, material
overrides, shadow flags, and collider generation. That made imported FBX/glTF
actors look format-specific and prevented a Unity-style component list where
rendering, collision, rigid body state, and material overrides are separate
authoring concepts.

The editor component system spec also requires stable actor/component IDs,
registered editor-visible components, Transform pinned at the top, and an Add
Component footer rather than an ad hoc button near Transform.

## Decision

- Actors now have stable editor-facing identity components (`ActorId`,
  `ActorName`) and repeatable authoring items use `ComponentInstanceId`.
- Editor-visible actor components are described by an
  `EditorComponentRegistry`; the Add Component footer reads from this registry.
- `InspectorOrder` stores editor component order plus per-component active
  state. Collapse state is session-only UI state; active state is persisted with
  the scene and is undoable.
- `StaticMeshRenderer` stores `MeshRenderSlot` values that reference imported
  content-browser assets through `EditorAssetRef { asset_id, sub_asset_id,
  label }`. Actor renderer data does not store source FBX/glTF paths.
- Static mesh hydration resolves `EditorAssetRef` through generated artifacts in
  `assets/meshes/generated/`.
- Collision and rigid body state are separate authoring components:
  `ColliderDesc` and `RigidBodyDesc`. Mesh collider generation creates
  `ColliderDesc::StaticMesh` instead of renderer collider flags.
- Materials are shader-schema aware. `MaterialDesc` stores a `ShaderRefDesc`,
  typed shader parameters, texture bindings, StandardMaterial fields, and
  optional asset references. When an actor has an active `MaterialDesc`, static
  mesh hydration uses it before imported slot/source materials. Slot material
  references remain source/default selectors, not a separate actor material
  editing surface. Shared material assets remain content-browser assets.

## Consequences

- New model placement creates `StaticMeshRenderer` plus optional
  `RigidBodyDesc`/`ColliderDesc`; legacy `PhysicsBody` remains loadable for old
  scenes.
- Actor inspectors show imported asset selectors for mesh/source-material slots
  instead of source-path text fields.
- Disabling a component in the inspector keeps its authoring data but prevents
  hydration/runtime systems from using it. Mesh, material, light, physics, and
  post-process hydration strip stale runtime components when active state
  changes.
- Existing static mesh artifacts without part IDs are still resolved by deriving
  stable sub-asset IDs from loader labels.
- Custom shader support is schema-driven; v1 stores and edits typed parameters,
  while runtime rendering currently maps built-in Lit/Unlit through Bevy
  `StandardMaterial`.