Struct Mesh2d 

pub struct Mesh2d {
    pub tris: Vec<SubTri>,
    pub axis: DropAxis,
    pub w0: Sign,
    pub unrecovered: usize,
    pub audit_needed: bool,
    pub coords: BTreeMap<Vid, Option<[f64; 2]>>,
}

The evolving 2D triangulation of T during phases C–E.

Fields

tris: Vec<SubTri>

axis: DropAxis

w0: Sign

unrecovered: usize

Constraint sub-segments the enforcement fixed point could NOT force as edges (degenerate channels the pocket rebuild bails on). Non-zero ⇒ the triangulation does not fully CONFORM to the other operand: sub-triangles may straddle an intersection line and their centroid classification is then unreliable. The batched void path treats this as a hard reject (fall back to sequential cuts); the binary path keeps its historical graceful-degrade behavior.

audit_needed: bool

Set by [recover_subsegment] whenever a recovery attempt could not force its edge (any bail path). Gates the final conformity audit in triangulate so the clean common path pays nothing for it.

coords: BTreeMap<Vid, Option<[f64; 2]>>

Per-Vid cached 2D f64 coordinate (dropped to axis, None when the implicit point has no finite f64 image). Used ONLY as a conservative broadphase prefilter in [insert_point] / channel detection — the exact predicate still decides every retained triangle, so this never affects topology. Cached because the same vertices are re-scanned on every point insertion AND on every constraint sub-segment’s O(tris) channel scan.