grid-apps-cmms/docs/void/plan-face-provenance.md

Void Face Provenance Plan (Boundary-First, Split Faces)

Goal

Track which portions of resulting solids come from which sketch extrude regions, including after union/subtract, while keeping storage compact and spline-ready.

Execution Status (2026-03-02)

Completed:

1. Plan authored and staged into phased implementation.
2. Debug visualization toggles added to preferences and wired to solids runtime:
3. Boundary loop rendering from GeometryStore.
4. Segment rendering from GeometryStore.
5. Segment/surface/region ID labels (overlay text).
6. Fixed world/local debug overlay transform bug:
7. GeometryStore points are world-space; line geometry parented under solids root must convert world -> root local because space.WORLD is rotated -90deg on X.

In progress:

1. Converting this plan into code-level milestone execution with strict acceptance checks.

Next up:

1. Add first surface_patch_id selection plumbing (read-only pass-through).
2. Thread Manifold relation metadata through kernel adapters.
3. Start mixed-face partition scaffold from seeded surface_patches.

Decisions

1. Primary provenance is boundary/region/surface-patch, not raw triangle ownership.
2. Triangle ownership is derived runtime index only (tri -> surface_patch_id) and can be rebuilt.
3. Multi-source output faces must be split into multiple bounded surface patches so each patch has one canonical source region.
4. Line/arc support ships first; segment model must support future spline kinds without schema redesign.

Scope

In scope:

1. Extrude + boolean provenance tracking through rebuild pipeline.
2. Face splitting by source-region boundaries.
3. GeometryStore schema extension for stable patch-level IDs and source refs.
4. Runtime mapping from picks (face/edge) to canonical patch and source region.

Out of scope (initial pass):

1. Native spline feature authoring.
2. Long-lived persisted triangle provenance tables.
3. Non-planar sketch-on-surface expansion beyond current behavior.

Data Model Changes

Add/extend document geometry_store entities:

1. segments[]

2. kind: line | arc | spline

3. geom: kind-specific payload

4. sampled_polyline (optional cache for hit testing/partitioning)

5. boundaries[]

6. Ordered segment_ids

7. closed, orientation, optional parent/child nesting

8. regions[]

9. outer_boundary_id

10. hole_boundary_ids[]

11. source: canonical source ref (profile:<sketch>:<profile>)

12. New surface_patches[]

13. id

14. surface_id (geometric carrier face)

15. boundary_ids[] (outer + holes)

16. source_region_id (single canonical owner)

17. source_feature_id (extrude feature)

18. solid_id

19. status (direct, boolean-derived, rebound)

20. New runtime-only topology.patch_tri_index

21. Maps mesh triangles to surface_patch_id for selection/render acceleration.

Kernel Boundary Changes (Manifold)

Current kernel adapter only round-trips positions/indices; relation metadata is dropped.

Planned update:

1. Preserve Manifold mesh relation fields where available (runOriginalID, faceID, related run metadata).
2. Carry relation metadata through extrudePolygons() and booleanMeshes().
3. Emit relation-aware intermediate records to rebuild stage (not directly persisted).

This enables deterministic attribution from boolean output back to input generated solids/regions before patch splitting.

Provenance Build Pipeline

Stage A: Sketch Region Capture

1. Keep current closed-loop profile extraction for line/arc.
2. Emit canonical region_id = profile:<sketch>:<profile>.
3. Record region boundaries using generic segment schema (line|arc now, spline later).

Stage B: Extrude Seed Patches

1. Extrude each selected sketch region.
2. Seed cap/side patch candidates with direct source region refs.
3. Preserve manifold relation fields in intermediate mesh record.

Stage C: Boolean Attribution

1. Perform add/subtract/intersect with relation-carrying meshes.
2. Build attribution map from output primitives/runs to source seed patches.
3. Mark ambiguous/mixed carrier surfaces for partitioning.

Stage D: Face Partitioning (Split Multi-Source Faces)

1. For each mixed carrier surface, project contributing source boundaries to surface-local space.
2. Build planar arrangement, split into disjoint bounded cells.
3. Assign each cell a single source_region_id by relation majority + geometric tie-break.
4. Emit one surface_patch per bounded cell.

Stage E: Runtime Topology Index

1. Build tri -> surface_patch_id map from patch partition output.
2. Use map for selection hit resolution and hover highlighting.
3. Rebuild index each solids rebuild; do not persist large triangle maps.

Selection/Interaction Integration

1. Face pick resolves to surface_patch_id first, then source_region_id.
2. Edge/boundary pick resolves to boundary_id/segment_id that belongs to a patch.
3. Extrude-profile hover/highlight uses source_region_id -> surface_patch[] mapping.
4. Remove fallback heuristics that infer provenance only from coarse source.profile_keys.

Storage and Performance

1. Persist compact canonical graph (segments/boundaries/regions/surface_patches).
2. Keep triangle-level maps runtime-only to avoid doc bloat and instability across remeshes.
3. Cache partition signatures per carrier surface to avoid full repartition when unchanged.

Migration Plan

Phase 1: Schema and Adapters

1. Add surface_patches schema and runtime index container.
2. Introduce generic segment schema (kind + geom) with current line/arc emitters.
3. Add compatibility normalizer for older docs (missing surface_patches).

Phase 2: Kernel Metadata Plumbing

1. Extend solid kernel adapter to preserve manifold relation metadata.
2. Pass relation metadata through worker/main rebuild paths.

Phase 3: Patch Builder

1. Implement mixed-face detection.
2. Implement local-space boundary arrangement and patch emission.
3. Add deterministic patch IDs/signatures.

Phase 4: Resolver Cutover

1. Switch face selection from coarse face groups to surface_patch entities.
2. Update properties/tree hover mapping to patch/source-region links.

Phase 5: Cleanup

1. Remove coarse provenance fallbacks once parity is validated.
2. Keep compatibility reader for older docs without surface_patches.

Validation Plan

Unit tests:

1. Region extraction determinism (line/arc).
2. Mixed-face partitioning into disjoint bounded patches.
3. Single-owner assignment per patch.
4. Deterministic patch IDs under stable input.

Integration tests:

1. Two extrudes unioned: top face splits by source boundary and highlights per profile.
2. Subtract operation: surviving walls/caps retain correct source region refs.
3. Edit upstream sketch profile: downstream patch mapping updates without manual repair.
4. Rebuild in worker vs main thread yields identical patch/source mapping.

Regression guardrails:

1. No persisted triangle tables in doc snapshots.
2. No schema changes required to add spline segment kind later.
3. Selection never reports mixed-source face entities.
4. Any debug/runtime geometry under solids root must explicitly convert GeometryStore world coordinates to root-local coordinates.

Implementation Checklist

Phase 1:

1. Done: update src/void/api/geometry_store.js schema to include surface_patches and runtime topology patch map container.
2. Done: extend buildGeometryStoreSnapshot() in src/void/api/solids.js to emit seeded surface_patches per face-loop with source-region candidate fields.
3. In progress: keep current face-key canonical mapping intact while adding optional patch ID fields.

Phase 2:

1. Update src/void/solid/kernel.js mesh conversion to preserve manifold relation fields:
2. Input pass-through where provided (runOriginalID, runIndex, faceID, etc.).
3. Output pass-through into rebuild intermediate structures.
4. Add worker payload support for relation arrays when present.

Phase 3:

1. Implement mixed-source detection in src/void/solid/rebuild.js.
2. Add per-surface local partition pass and emit patch boundaries.
3. Assign one canonical source_region_id per patch.

Phase 4:

1. Extend selection resolver and solids hit mapping to prefer patch IDs over raw face IDs.
2. Add properties/tree hover mapping from extrude profile -> patch IDs.
3. Remove coarse fallback once parity checks pass.

Phase 5:

1. Add deterministic integration tests for union/subtract split-face provenance.
2. Remove temporary migration branches and finalize docs.

Acceptance Criteria

1. Every selectable resulting face area maps to exactly one source_region_id.
2. Multi-source carrier faces are visibly and topologically split at source boundaries.
3. Extrude profile hover/select maps accurately to resulting solid patches after booleans.
4. GeometryStore stays compact and stable; triangle mapping is derived at runtime.