nx_facs.nx

nx_facs.nx -- ★FACIAL ACTION CODING AS DATA: the expression basis, separated from identity. ★THE DEFECT THIS FIXES, and this codebase has cured it once already. nx_anatstack drives expressions from `AS_EXPR`, a SINGLE ENUM (0 neutral, 1 smile, 2 surprise, 3 frown) fed to an if-chain of hardcoded part indices and magnitudes. Two consequences, and the second is structural: (a) expressions are CODE, not data -- adding one means editing a function; (b) ★★ONLY ONE EXPRESSION CAN EXIST AT A TIME. You cannot smile AND raise a brow. A real face is always a COMBINATION, so the enum cannot represent even ordinary human faces. ★nx_skelgen already wrote the cure for exactly this shape: "THE BODY PLAN AS DATA -- until now the plan WAS the code: a chain of if b == n ... that works for exactly one species and one subject." Same disease, same fix: a TABLE. ★★★AND THE RIGHT TABLE IS FACS, BECAUSE OUR EXPRESSIONS ARE MUSCLE-DRIVEN. An Action Unit IS a named muscle action (AU12 = zygomaticus major, AU4 = corrugator), so for an anatomically-driven stack the standard basis and the physical basis are THE SAME THING. Google's GNM spends 150 statistical parameters on the lower face; a causal system needs ~30 named muscle actions to span the same space, because each one means something. **That is our exceed axis: expression by CAUSE, not by fit.** SEPARATION OF CONCERNS, which is GNM's first architectural idea: IDENTITY is the anthropometric parameter set (who the face is); EXPRESSION is an AU WEIGHT VECTOR (what it is doing). They no longer share a representation and can be solved independently. nx_facs selftest license_tier: ORIGINAL expect_exit: 0 No hw writes (Rule 26).