nx_step_tess.nx

nx_step_tess.nx -- PLANAR-FACE TESSELLATION from STEP B-rep (cadtwin P3a geometry half): turn the file's actual topology into real triangles. Walk ADVANCED_FACE -> bound -> EDGE_LOOP -> ORIENTED_EDGE (.T. start / .F. end vertex) -> EDGE_CURVE -> VERTEX_POINT -> CARTESIAN_POINT; project the loop onto the PLANE's 2D basis (origin/normal/refdir from AXIS2_PLACEMENT_3D); EAR-CLIP the polygon (integer 2D cross products -- correct for CONCAVE faces like the L-bracket, where a naive fan is wrong); emit triangles into mesh3. SELF-CHECK invariant: the signed ear areas must sum EXACTLY to the polygon shoelace area (same integer coords) -- any ear-clip bug shows as a mismatch count, not silent bad geometry. HONEST scope v1: single-bound planar faces; multi-bound (holes/rims), curved surfaces (cylinder/B-spline) counted+skipped; curved EDGES on planar faces become chords (counted). Composes nx_step_geom (STEP reals) + nx_mesh3. license_tier: ORIGINAL