Walkability topology

WalkabilityService converts a complete geometry scene into a source-neutral graph of derived walkable regions. Axiolid or another trusted geometry backend owns free-space extraction, obstacle subtraction, portal verification, and region decomposition.

The request supplies deterministic source-qualified sets of:

• walkable surface objects;
• entrance or portal objects;
• obstacle objects;
• the required clear width and optional elevation band;
• verified-portal and moving-envelope policy.

Semantic selectors run before this service. IFC placements, meshes, B-reps, and native kernel types never enter the request.

Snapshot guarantees

A WalkabilitySnapshot is accepted only when it carries complete exact provenance. Every passage must have exact reviewable evidence, declared endpoints, and a conservative clear-width interval. Duplicate passages, unrequested object mappings, and portals outside the request policy are rejected.

Object-to-region membership lets reusable capabilities ask whether selected spaces, entrances, or components share traversable free space without exposing backend cells as model objects.

Three-valued routes

For the request minimum width, the engine evaluates two deterministic graphs:

1. definite graph: passage lower bound meets the width;
2. possible graph: passage upper bound meets the width.

A route in the definite graph is Reachable. No route in the possible graph is Unreachable. A route only in the possible graph is Indeterminate. Approximate width evidence therefore cannot become a pass or a false negative.

Corridor metric lengths remain owned by the separate metric-routing service. End-clearance placement remains owned by the free-space placement service.