Crate axiolid_ray_mesh 

Narrow-phase ray/triangle-mesh nearest-hit intersection.

Why this is its own package

axiolid-spatial already owns the broad phase: SpatialIndex::visit_ray walks a BVH and yields candidate keys. Without a narrow phase a caller gets boxes and has to write ray/triangle themselves, which is how tolerance policy fragments across consumers. This package closes that seam and owns nothing else.

It deliberately does not depend on axiolid-spatial: the narrow phase is useful without an index, and an index is useful without this. Composition happens at the call site by feeding candidate triangle indices into nearest_hit_among.

Boundary

This package owns the intersection and the hit record. It does not own what a ray means: sampling patterns, camera rigs, entity identity, or whether a hit counts as an obstruction stay with the caller.

Fail closed, never silently miss

A degenerate (zero-area) triangle has no well-defined ray intersection. This package refuses with RayMeshError::DegenerateTriangle rather than reporting a miss, because a silent miss is indistinguishable from real empty space and quietly corrupts containment and visibility answers built on it.

Ray direction is not required to be normalised, so the reported t is in units of the supplied direction vector. That is stated rather than fixed up, because normalising a caller’s ray silently changes the meaning of every distance they compare against.

What the tolerance decides

Tolerance::linear() bounds only the parallel-ray rejection and the barycentric slack that keeps edge and vertex hits. It never decides the front/back branch: FaceSide comes from the certified orient3d sign.

Structs

RayHit3

One nearest-hit record.

Enums

FaceSide

Which side of a triangle the ray arrived from.

RayMeshError

Fail-closed reasons a ray/mesh query cannot produce an answer.

Functions

intersect_triangle

Intersect a ray with a standalone triangle.

nearest_hit

Nearest hit over every triangle of mesh.

nearest_hit_among

Nearest hit over caller-supplied candidate triangles.

triangle_hit

Intersect one triangle of mesh, reporting the hit or a certified miss.