CultLib/src/GameCult.Geometry/README.md

# GameCult.Geometry

`GameCult.Geometry` defines shared geometry values plus CultCache-native
documents for procedural geometry domains, LOD build requests, selected-cut
manifests, and mesh chunk artifacts.

The package is deliberately substrate-shaped:

- CultCache owns document identity, schema compatibility, references, and local
  persistence.
- CultNet can distribute these documents through the normal raw document lane.
- CultMesh can use them as worker-visible shared state for simulation and
  geometry pipelines.
- JSON is not a runtime transport here. It may publish schema descriptions at
  the xeno boundary, but the live machine eats and emits typed CultCache
  documents.

## Value Primitives

The small value layer is for cross-runtime query contracts, physics probes,
native slices, and UI surfaces:

- `CultVec2` and `CultVec3`: whole-vector values for positions, velocities,
  accelerations, and query inputs. SoA layouts may store them efficiently, but
  the semantic API does not force callers to split x/y/z into unrelated fields.
- `CultRect`: canonical XY viewport/query rectangle stored as min/max corners.
- `CultCircle`: 2D influence/query brush with rect intersection helpers.
- `CultSphere`: 3D query primitive with whole-vector center and XY projection.

Aetheria object viewports, gravity influence brushes, Ymir overlap/cast query
fixtures, and Unity native render views should use these shapes or generated
runtime equivalents instead of bespoke `{ minX, minY, maxX, maxY }` payloads.

## Runtime Path

`vg-csg` emits domain documents, selected-cut manifests, and chunk artifacts as
MessagePack CultCache documents. A Unity runtime, local worker, or remote
geometry process should receive the same records through CultMesh/CultNet and
read them back as `CultGeometry*` types.

```csharp
using GameCult.Caching;
using GameCult.Geometry;
using GameCult.Mesh;
using GameCult.Networking;

var geometryDocuments = new CultNetDocumentRegistry(CultDocumentRegistry.Shared)
    .Register(CultNetDocumentBinding.ForDocument<CultGeometryDomainDocument>())
    .Register(CultNetDocumentBinding.ForDocument<CultGeometryBuildRequest>())
    .Register(CultNetDocumentBinding.ForDocument<CultGeometrySelectedCutManifest>())
    .Register(CultNetDocumentBinding.ForDocument<CultGeometryChunkArtifact>());

using var node = await CultMesh.CreateNodeAsync("ragnarok-geometry.ccmp", new CultMeshNodeOptions
{
    DatabaseOptions = new CultNetDatabaseOptions
    {
        RuntimeId = "unity-runtime",
        DocumentRegistry = geometryDocuments
    }
});

using var chunks = node.Database
    .Watch<CultGeometryChunkArtifact>()
    .Subscribe(change => ApplyChunk(change.Document));
```

The record key is part of the contract. Rust and C# must compute the same key
for the same geometry record, so stable fingerprints use the Rust canonical
field order and invariant float text. If this drifts, the same chunk becomes two
different chunks depending on which runtime touched it first. That is not a
cache miss; that is split-brain geometry.

## Documents

- `CultVec2`, `CultVec3`, `CultRect`, `CultCircle`, `CultSphere`: shared value
  primitives for query and view contracts.
- `CultGeometryDomainDocument`: one hierarchical domain tree, suitable for
  Ragnarok/Fensalir-style feature DSL output.
- `CultGeometryBuildRequest`: one LOD/frustum/budget request for workers.
- `CultGeometrySelectedCutManifest`: the selected domain cut, deferred children,
  fallback rows, and diagnostic contribution rows.
- `CultGeometryChunkArtifact`: render mesh, optional collider mesh, source
  domain/claim identities, build counters, and transition clipping seed.