open-wc/docs/modules/m2-mesh-resource-cache-state.md

M2 Mesh Resource Cache State

Metadata

Field	Value
Status	Implemented extraction
Target/work package	M03 / M03-RND-M2-MESH-RESOURCE-CACHE-001
Owners	Prepared static M2 Mesh resource references by normalized path
Last verified	Worktree work/sindo-main-codex/m03-m2-mesh-resource-cache, 2026-07-17
Profiles/capabilities	Existing static M2 cached and raw fallback paths

Purpose

Own the runtime cache of prepared static M2 Mesh references outside StreamingWorldLoader. Dedicated services extract and prepare each Mesh; the loader remains responsible for finding, loading, adopting and materializing it.

Non-goals

• Own the shared M2 missing-path, prototype or animated-scene caches.
• Call ResourceLoader/FileAccess or select .tscn/.glb paths.
• Extract a Mesh from a Resource or Node.
• Refresh materials, rebuild Meshes or create MultiMesh instances.
• Add eviction, persistence, cache versions or quality-profile behavior.

Context and boundaries

flowchart LR
    Need[Static M2 mesh lookup] --> Loader[StreamingWorldLoader]
    Loader --> Cache[M2MeshResourceCacheState]
    Cache -->|cached Mesh or null| Loader
    Loader --> Pipeline[M2MeshLoadPipelineState]
    Pipeline --> IO[ResourceLoader]
    IO --> Extract[M2MeshResourceExtractor]
    Extract --> Prepare[M2RuntimeMeshFinalizer]
    Prepare --> Cache
    Loader --> Build[M2 MultiMesh materialization]

The cache may retain Mesh resources and copied normalized-path Strings. It has no Node, ResourceLoader, filesystem, worker, scheduler, missing-state, builder, gameplay, network or editor dependency.

Public API

Symbol	Kind	Purpose	Thread/lifetime	Errors
store_mesh(path, mesh)	Command/query	Retain or replace one prepared Mesh	Renderer main thread; final shutdown	Empty path/null Mesh rejected
has_mesh(path)	Query	Test whether a Mesh is retained	Renderer main thread	Empty/unknown false
find_mesh(path)	Query	Borrow exact retained Mesh reference	Renderer main thread	Empty/unknown null
mesh_count()	Query	Return retained entry count	Diagnostics/tests	None
normalized_paths_snapshot()	Query	Copy insertion-order path keys	Diagnostics/tests	Never exposes Mesh references
clear()	Command	Release every retained Mesh reference	Final shutdown after async drain	Idempotent

Inputs and outputs

Direction	Contract/data	Producer	Consumer	Ownership	Thread/lifetime
Input	Normalized relative M2 path	Loader normalization adapter	Cache key	Copied String	Cache lifetime
Input	Prepared static Mesh	Loader finalizer or synchronous fallback	Cache value	Strong reference retained	Until replacement/clear
Output	Borrowed exact Mesh	Cache lookup	Static M2 batch builder	Cache retains reference	One build/materialization pass
Output	Detached normalized paths	Cache diagnostics	Verifier/future metrics	Caller-owned Strings	Snapshot lifetime

Store and clear mutate only the cache Dictionary and Resource reference counts.

Data flow

flowchart TD
    Lookup[Lookup normalized M2 path] --> Cached{Mesh cached?}
    Cached -->|yes| Return[Return retained Mesh]
    Cached -->|no| Missing{Shared missing state?}
    Missing -->|yes| Null[Return null]
    Missing -->|no| Load[Loader request or synchronous fallback]
    Load --> Prepare[Extractor and runtime finalizer prepare Mesh]
    Prepare --> Valid{Prepared Mesh valid?}
    Valid -->|yes| Store[Store or replace cache entry]
    Valid -->|no| MarkMissing[Loader updates shared missing state]
    Store --> Return

Lifecycle/state

stateDiagram-v2
    [*] --> Absent
    Absent --> Cached: store valid Mesh
    Cached --> Cached: replace Mesh reference
    Cached --> Absent: final shutdown clear

Map/world refresh retains cached Meshes. Only the existing final runtime-cache release clears them after asynchronous shutdown drain.

Main sequence

sequenceDiagram
    participant Loader as StreamingWorldLoader
    participant Cache as M2MeshResourceCacheState
    participant Pipeline as M2MeshLoadPipelineState
    Loader->>Cache: find/has normalized path
    alt cache miss
        Loader->>Pipeline: request/poll/finalize record
        Loader->>Loader: ResourceLoader get; delegate extract + prepare
        Loader->>Cache: store_mesh(path, prepared Mesh)
    end
    Cache-->>Loader: exact retained Mesh
    Loader->>Loader: materialize static M2 batch

Dependency diagram

flowchart TB
    Loader[StreamingWorldLoader] --> Cache[M2MeshResourceCacheState]
    Loader --> Pipeline[M2MeshLoadPipelineState]
    Loader --> Finalizer[M2RuntimeMeshFinalizer]
    Loader --> Builder[M2Builder and MultiMesh]
    Cache --> Mesh[Godot Mesh Resource]
    Cache -. no dependency .-> Pipeline
    Cache -. no dependency .-> Classifier
    Cache -. no dependency .-> Builder

Ownership, threading and resources

• Renderer main-thread adapters serialize every cache operation.
• The cache owns normalized-path Strings and strong Mesh references.
• Borrowed Mesh lookups do not transfer ownership or duplicate resources.
• M2MeshResourceExtractor owns first-Mesh selection and temporary PackedScene instances. The loader owns missing/prototype/animated state and MultiMeshes.
• The loader drains asynchronous work before the final cache clear.

Errors, cancellation and recovery

Failure/state	Detection	Behavior	Diagnostic	Recovery
Empty path or null Mesh	Cache guard	Reject unchanged	Contract verifier	Correct caller input
Unknown lookup	Membership query	Return null	Existing loader path	Request/load or missing decision
Replacement	Existing key	Retain new exact reference	Contract verifier	Normal subsequent lookup
Load/preparation failure	Loader boundary	Do not store; loader marks missing	Existing renderer behavior	Cache/source correction and reload
Final shutdown	Loader lifecycle	Clear releases references	Shutdown/source verifier	New loader starts empty

Configuration and capabilities

The module adds no setting, budget or profile branch. Cache path order, finalize permits and batching remain loader-owned; refresh version 2 belongs to M2RuntimeMeshFinalizer.

Persistence, cache and migration

The state is runtime-only and serializes nothing. Existing .tscn/.glb formats, import caches and material refresh metadata are unchanged; no migration or rebake is required.

Diagnostics and observability

mesh_count and normalized_paths_snapshot expose scalar ownership diagnostics without Mesh references. Existing renderer metrics/logging are unchanged because the historical Mesh cache had no queue contribution or log site.

Verification

• verify_m2_mesh_resource_cache_state.gd: invalid input, exact reference, replacement, lookup, detached path snapshot, idempotent clear, loader source ownership and 100-by-256 bounded timing.
• Mesh pipeline/classifier/material/shutdown/M2 build/facade regressions cover adjacent behavior.
• Fidelity evidence is exact cache/lifetime extraction; no original-client visual-parity or asset-backed performance claim is made.

Extension points

• M2RuntimeMeshFinalizer returns a prepared Mesh for store_mesh without changing cache ownership.
• Eviction requires measured memory pressure and explicit lifetime semantics.

Capability status

Capability	Status	Evidence	Gap/next step
Prepared static M2 Mesh cache	Implemented extraction	Contract/source/timing verifier	Asset-backed memory/leak run pending
M2 Mesh request lifecycle	Implemented extraction	Pipeline state verifier	ResourceLoader I/O remains loader-owned
M2 Mesh extraction	Implemented extraction	Resource/order/lifetime verifier	Asset-backed corrupt-scene fixture pending
M2 Mesh preparation	Implemented extraction	Runtime finalizer transition/rebuild verifier	Asset-backed material comparison pending

Known gaps and risks

• Strong Mesh references intentionally remain until final shutdown.
• Shared missing state cannot move here without also redesigning prototype and animated lookup behavior.
• No proprietary M2 traversal, leak/descriptor-pressure, p95/p99 or paired original-client capture is included.

Source map

Path	Responsibility
src/render/m2/m2_mesh_resource_cache_state.gd	Prepared Mesh references and final clear
src/render/m2/m2_mesh_resource_extractor.gd	First-Mesh selection and temporary PackedScene lifetime
src/scenes/streaming/streaming_world_loader.gd	Normalization, raw/resource I/O, missing state and materialization
src/render/m2/m2_runtime_mesh_finalizer.gd	Refresh/rebuild/fallback preparation
src/render/m2/m2_mesh_load_pipeline_state.gd	Pending request and terminal finalize records
src/tools/verify_m2_mesh_resource_cache_state.gd	Cache ownership/lifetime/boundary/timing regression

Related decisions and references

• m2-mesh-load-pipeline-state.md
• m2-runtime-mesh-rebuild-classifier.md
• world-renderer.md
• ../../RENDER.md
• ../../targets/roadmap/02-rendering-and-graphics.md