Module section 

Portable scalar plane section of a closed oriented triangle mesh.

Topology is classified from the exact binary64 plane equation. Geometry is emitted in the caller’s plane frame, with source-edge connectivity preserved; no tolerance-based point welding is used.

Two entry points share the exact vertex classification and segment building:

• section is the legacy path. A face lying in the plane is refused as degenerate, and its messages are part of its contract.
• section_request (ADR 0091) reports faces lying in the plane as regions with a side, keeps cut curves to transversal crossings, and counts touching edges. request orchestrates it, regions traces the region boundaries and chains assembles open and closed chains.

Structs

ScalarSection

Portable deterministic mesh plane-section oracle.