Function face_contains 

pub fn face_contains<S: Scalar>(
    model: &Model<S>,
    face_id: FaceId,
    u: S,
    v: S,
    max_nodes: usize,
    epsilon: S,
    seed: u64,
) -> GeopResult<PointClassification>

Classify (u, v) against face_id’s trimmed boundary (outer loop minus holes): PointClassification::OnVertex / PointClassification::OnCoedge if the query point itself coincides with a vertex or lies on a coedge’s pcurve, else PointClassification::Inside/PointClassification::Outside via ray casting in parameter space.

The ray direction is drawn from a seeded PRNG (see Rng) and retried (up to a bounded number of attempts) until every crossing it finds lands strictly inside a coedge’s pcurve, away from any vertex — vertex grazes are ambiguous to count (shared by two coedges) so they’re avoided rather than specially classified. Once such a direction is found, the parity (even/odd) of its crossing count determines inside/outside; this needs no normal or winding-direction information, so it works regardless of a face’s loop orientation.

max_nodes bounds both the curve_could_contain BFS subdivision search (on-vertex/on-coedge tests) and the curve_curve_intersect DFS search (edge-interior hits). seed seeds the direction PRNG.