nx_skull_canon_lib.nx

nx_skull_canon_lib.nx -- THE GENERATED SKULL'S OWN RULER: craniometric landmarks on OUR skull and on the scanned oracle by ONE locator, compared in a landmark-defined frame, with bands measured off the resource (anatomy AN17, 2026-09-18). WHY: knowledge/status/skullfit_trend.jsonl scores the generated skull as millimetres per REGION against the oracle surface, and its regions are dominated by the vault and the base (n_ours 9,335 + 8,672 of about 31,000 samples), so a lumpy ovoid with a 49 mm muzzle reads "4 mm mean" and its nasal region reads n=0. This library measures the FACE: the craniometric landmarks that decide whether a skull reads as a skull (chin depth, the nasal aperture's position, height, width and depth, the orbits' centres, widths and depths, the bizygomatic and bigonial breadths, the prosthion, the bony thirds), each located by the SAME rule on both skulls, so every number is a difference between two measurements and never a difference between two definitions. COMPOSES, NEVER RE-IMPLEMENTS: the landmark locator is nx_tissuefield_lib.tfl_locate (midline-profile extrema by noise-floor prominence, support directions, rim crests); the mesh reader is its NXMSH2 welder (tfl_mesh_load); the frontal depth map is its tfl_front_at. Added here, because a face ruler needs them and the locator does not name them: (1) the opisthocranion (the point farthest from the glabella: maximum cranial length) and the euryons (the most lateral points above the brow) as chords and supports; the piriform aperture by its RIMS (rhinion and nasospinale on the midline, the lateral margins as rim crests walked by the locator's own tfl_crest rule) and the orbits by theirs (the locator's supraorbital, infraorbital and ectoconchion crests plus a medial crest walked here), so widths, heights and depths are rim-to-rim or rim-to-floor and a see-through hole reads DEEPER than any socket; (2) THE FRAME: a translation to the nasion and no rotation (skc_frame says why); the rotation it refuses to apply -- the glabella-opisthocranion chord's pitch -- is a measured quantity of its own; (3) THE BANDS: the locator's own noise, measured by re-locating on rigidly perturbed copies of the same mesh (a half-edge translation, a pitch and a yaw that move the vertex by one mesh edge), floored at the mesh's own resolution (a vertex set e apart cannot place a point better than e/2); a paired landmark adds the oracle's own bilateral asymmetry. Two further perturbations (a negative translation, a roll) are HELD OUT so a gate can ask whether the bands generalise instead of reading them back to itself; (4) THE MIDLINE RULES of tfl_locate with two changes, both measured on the scan and filed for the locator's owner: the aperture is the most PROMINENT minimum, never the smallest absolute z; the glabella is the most anterior point above the aperture floor and the pogonion the most anterior maximum below the prosthion (skc_midline_locate). FRAME CONVENTION: +y up, +z anterior, x lateral (nx_skullsdf emits so). The BodyParts3D oracle in knowledge/skull.nxmesh is stored anterior -z, exactly as nx_skullsdf's own tune (ss_load_ref) and gapmap read it, so skc_load(path, 1) negates z on load; a reflection through the coronal plane is a rotation by half a turn about y for a bilaterally symmetric skull, so widths and midline coordinates are unaffected and the pair names are read as a PAIR, never as sides. UNITS: the welder's u10 (tenths of a millimetre). LIB, no main. license_tier: ORIGINAL No hw writes (Rule 26).