nx_geo_segint.nx

nx_geo_segint.nx -- LIB: GEO-015b SEGMENT-SEGMENT INTERSECTION primitive (the building block for non-convex polygon clipping / Greiner-Hormann, hardening GEO-015/016 toward real boundary polygons). Parametric: P1 + t*(P2-P1) = P3 + u*(P4-P3). With d1=P2-P1, d2=P4-P3, e=P3-P1: denom = cross(d1,d2); t = cross(e,d2)/denom; u = cross(e,d1)/denom. All INTEGER cross products -> the topological classification is EXACT and deterministic: 0 = no intersection (parallel-disjoint, or lines meet outside one of the segments) 1 = proper interior crossing (single point, strictly inside both) 2 = touch at an endpoint (t or u exactly 0 or 1) 3 = collinear (overlapping supports) The intersection POINT (codes 1,2) is written to out2 = [x,y], microdeg-rounded, with the t fraction normalized (lockstep >>1) so P1 + t*d1 can't overflow i64 at any scale (same trick as GEO-015). Generic 2D (caller maps lat/lon as it likes). license_tier: ORIGINAL