nx_curveskel_lib.nx

nx_curveskel_lib.nx -- SOVEREIGN SKELETON-FIT: extract a curve skeleton (an armature) from a BARE unrigged mesh. WHY (2026-09-05). nx_boneheat ships the SKIN half of auto-rig, and its accept rule needs a skeleton to weight against. Blender's Rigify only assembles a CONTROL rig from a meta-rig a human PLACES by hand -- its own manual says it does not attach to a mesh -- and UniRig/RigNet predict a skeleton with a LEARNED model over a training set. Neither is sovereign-from-the-first-byte for an arbitrary mesh. This is the classical route done right: a deterministic integer CURVE SKELETON by geodesic farthest-point peeling, needing no checkpoint and no data. 1. VOXELISE + SEAL the mesh volume -- COMPOSED from nx_boneheat_lib (bh_grid_build/bh_raster/bh_flood), the SAME voxeliser the skin solve uses, so the two halves cannot disagree about the volume. Interior 0 (a sheet with no volume) is REFUSED by name. 2. MEDIAL RADIUS field: multi-source Dijkstra seeded from EVERY surface cell over the domain -> each interior cell's distance to the nearest surface = its local half-thickness. The ROOT is the thickest interior cell. 3. PEEL limbs: seed the current skeleton set, Dijkstra, take the geodesically FARTHEST interior cell as a limb tip, and gradient-descend the geodesic field from the tip back to the skeleton -- that path IS a bone chain. Repeat until the farthest remaining point is closer than the body's own half-thickness (a derived stop, not a magic number: a bump thinner than the torso is not a limb). This is the shortest-path curve-skeleton family (Verroust-Lazarus class), integer and deterministic. 4. SAMPLE joints along each chain spaced by the LOCAL medial radius (thick regions sparse, thin regions dense -- derived from the field), parent-chained, the first joint of a limb parented to the nearest existing joint so branches (a T or a cross) form real fork joints. Emit a SKEL section; nx_boneheat skins it. Safety caps CS_MAX_JOINTS / CS_MAX_LIMBS are NAMED bounds on output size and ANNOUNCE truncation; they are not tuning. UNITS: VERT is 0.01 mm model units (NXA v1); joint positions are cell centres in the same units. license_tier: ORIGINAL