cockpit/torso: anisotropic surface-fit splat + per-node SoA + /torso-map

The structural upgrade you greenlit: the torso splat stops being a detached
isotropic point cloud and becomes the GUID/value-tenant substrate seen as
oriented geometry. One pass over the BodyParts3D meshes does all of it.

SPL2 format (supersedes SPL1): hdr 40B [SPL2|count|node_count|radius|bbox];
body 21B [pos 3f | normal 3i8 | rgb 3u8 | opacity u8 | node_row u16]. Helix-
orderable + residual-ready (the Helix-48 codec slots in here next).

- Anisotropic surface-fit ("connect the dots"): BodyParts3D OBJ ships per-vertex
  normals (vn) — free, no face traversal. The splat3d render driver orients each
  gaussian flat-to-surface (scale=[t,t,thin], quat aligns local-z to the normal);
  tangent 0.004 connects within a structure while rib gaps stay visible. Oriented
  disks blend into continuous surfaces with real 3D form — not isotropic blobs,
  not a discrete voxel grid.
- Per-node SoA + O(1) switch (the GUID backbone): torso.nodes.json = one row per
  FMA structure (178 rows, 91 own meshes) carrying the value-tenants of one
  identity — fma id, name, depth, HHTL tier-ranks, colour, gaussian RANGE
  (start+count), and the OBJ-geometry tenant (centroid+bbox+FJ handles). Each
  gaussian carries its node_row; consumers build the switch (row->node) once ->
  O(1) tenant reads. Position = real BodyParts3D coordinate; identity = FMA node.
- /torso-map (TorsoMap.tsx): click a gaussian -> node_row -> O(1) into the SoA ->
  FMA label + partonomy breadcrumb; structure list highlights its gaussians
  (graph <-> splat). The osint-cad-splat thesis made literal: graph and splat,
  one node at one address, switch-selected.
- /torso-live decodes SPL2 (still points); /torso shows the re-rendered
  anisotropic turntable. main.tsx: /torso-map route.

Verified by viewing the rendered frames (connected anatomical surfaces, upright,
form from orientation). tsc clean; browser pick-interaction not exercised here
(raycast-on-Points is standard). Geometry: BodyParts3D, CC-BY 4.0 / CC-BY-SA 2.1
JP, (c) The Database Center for Life Science (attribution in-view).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TzqvDqbFRzyx17EkLKBoZF

Author: claude

claude-notes/plans/2026-06-24-fma-torso-bodyparts3d-splat.md

@@ -62,22 +62,31 @@ Notes:
   brush blobbed the detail into a "Warhol" look; 0.0025 at 810x1080 restores the
   ribcage/vertebrae). Frames re-rendered.
 
-## Follow-ups (proposed, next PR)
+## Follow-up PR — anisotropic + GUID-tag + map (branch claude/torso-anisotropic-map)
 
-The splat is currently isotropic spheres (no orientation) — too big = blobs,
-too small = disconnected dots. The real upgrade, in one pass over the meshes:
+- [x] **SPL2 format** (supersedes SPL1): hdr 40B [`SPL2`|count|node_count|radius|
+      bbox]; body 21B [pos 3f | normal 3i8 | rgb 3u8 | opacity u8 | node_row u16].
+      Helix-orderable + residual-ready (the codec PR slots in here).
+- [x] **Anisotropic surface-fit gaussians** ("connect the dots"): bake reads OBJ
+      `vn` (BodyParts3D ships normals — free, no face traversal); render driver
+      orients each gaussian flat-to-surface (`scale=[t,t,thin]`, `quat` aligns
+      local-z to the normal). Tangent 0.004 connects within a structure while
+      rib gaps stay visible. NOT voxels (continuous surfaces, not a discrete grid).
+- [x] **Per-node SoA + O(1) switch** (the GUID/value-tenant backbone): bake emits
+      `torso.nodes.json` — one row per FMA structure (178 rows, 91 own meshes):
+      fma id, name, depth, HHTL tier-ranks, colour, gaussian RANGE (start+count),
+      OBJ-geometry tenant (centroid + bbox + FJ handles). Each gaussian carries
+      its node_row. Consumers build the switch (row -> node) once -> O(1) tenant
+      reads. Position = real BodyParts3D coordinate; identity = the FMA node.
+- [x] **/torso-map page**: click a gaussian -> node_row -> node SoA -> FMA label +
+      partonomy breadcrumb; structure list (graph -> splat) highlights gaussians.
+      Realises the osint-cad-splat thesis: graph and splat, one node at one address.
+- [x] tsc clean. Browser pick-interaction not exercised here (raycast-on-Points
+      logic is standard; geometry verified via the CPU frames).
 
-- [ ] **Anisotropic surface-fit gaussians** ("connect the dots"): read OBJ
-      *faces* (the bake currently drops them) -> per-vertex normals -> orient
-      each gaussian flat-to-surface (`scale[3]` tangent-wide / normal-thin,
-      `quat` from normal). splat3d's `Gaussian3D` already supports scale+quat;
-      the three.js page needs a real splat shader (oriented quads). This is the
-      "muscle memory of the nodes" — each gaussian inherits its shape from the
-      structure it came from. NOT voxels (those are discrete/volumetric; these
-      are continuous surfaces).
-- [ ] **Third "map FMA" view**: bake a per-gaussian FMA structure id + legend
-      (idx -> FMA concept / name / colour) into SPL1, then pick-to-label in 3D
-      and sync selection with the /fma-style partonomy graph. Realises the
-      osint-cad-splat thesis: graph and splat are one node at one address, two
-      payloads. Own page (/torso-map) vs folding labels into /torso-live: TBD
-      with user.
+## Next PR — Helix-48 residue codec (queued)
+
+Order gaussians along the helix (= Morton/Vogel identity order = GUID order),
+bake appearance into the 48 SH (shading vs flat — pending user), x265-style
+residual-code the SH along the curve. The asset byte-order becomes the node
+identity order, codec-compressed. SPL2 is laid out ready for it.