nx_mesh_sculpt.nx

nx_mesh_sculpt.nx -- ZBrush-class curved primitive + sculpt brush, sovereign. Closes the "curved geometry + sculpting" gap on the mesh kernel. Builds an icosphere by subdividing an octahedron and projecting every vertex onto the sphere with integer nx_isqrt (NO trig, NO f64 -- both unreliable here), then a radial "inflate/draw" brush that pushes verts within a brush radius outward along their normal with a smooth (linear) falloff. For an origin-centred primitive the outward radial direction IS the surface normal, so this is a correct draw brush on the sphere; general per-vertex normals are a follow-up. Reuses nx_mesh_subdivide (nx_mesh_edit) + nx_isqrt. No dup: grepped, none existed. Output is pipeline-native Q14-mm -> flows to nx_stl_write_mesh. license_tier: ORIGINAL.