The song brings a body, not only an outline

A silhouette is the same picture from every angle, so a scene that turns one is
showing you the same shape rotated. That is the ceiling the cast has been under:
it can be notched and hollowed and it still cannot be walked around.

So the identity generates an ASSEMBLY — two to six parts, each a primitive with
an offset, a scale, a rotation and a boolean op, all under a symmetry. The
symmetry is the load-bearing half: parts unioned at random positions read as
debris, the same parts folded read as designed, and only a designed object is
worth calling a protagonist. Prism parts are the existing 2D profile extruded,
so the solid and the silhouette stay one character rather than two generators
running side by side.

It travels as data like every other artifact: three vec4 rows per part in
u_formPart, plus the scalars. Scenes declare `consumes: ['form']` and get
castSDF3, castMarch, castSolid, castChorusSolid and castLit; with no identity
they fall back to the flat profile extruded, so the helpers are safe to call
unconditionally. The chorus is the same rows with fewer parts and its own
proportions — a relative, not a second generator, and no extra uniforms.

Three scenes carry it. Effigy is new and holds the object still while it turns.
Floating Geometry and Swarm were already loops of stamps and are now loops of
bodies; Swarm is what the chorus solid exists for. That is 34.8% of videos
containing a 3D cast, against 11.9% when only Effigy had it.

Measured, the outline does change rather than merely spin: over one turn the lit
area of Effigy's subject varies 14-113% against Soloist's 3-51% for the same
rotation. Whether that reaches the variety blocks is not yet measured, and
HOWTO-variety says so rather than claiming the win.

Four costs, each found by measuring rather than by reading:

  * every pixel evaluated every instance's field — Swarm at 59ms/frame against a
    60ms ceiling. Bounding-sphere reject first, now 12.3ms.
  * instances overlap several deep at the top of the size range, and marching
    all of them made Floating Geometry's own gate run for minutes. First-wins
    instead of last-wins, which was arbitrary either way.
  * a normal inside the march loop multiplies four copies of the SDF by the step
    count, because GLSL unrolls a fixed bound. Hoisted out.
  * the helpers in the shared preamble made all 68 scenes compile what 3 of them
    call. FORM_PREAMBLE is appended per scene instead.

The lint's backtick check was green through two of my own breakages: quoting a
name in a doc comment adds backticks in PAIRS, so parity survives and the
pair-scanner just re-partitions the file. It now finds where a shader literal
opens and requires the next backtick to be a real terminator — which
immediately found a second stray pair.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

flow-state/HOWTO-variety.md

@@ -113,6 +113,25 @@ scene also carries the identity better than a stage written from scratch to
 carry it, which was a surprise and is why the whole library was migrated rather
 than replaced.
 
+### 1b. Give the subject a third dimension — payoff still unmeasured
+
+`castSolid` / `castChorusSolid` / `castMarch`, and `consumes: ['form']`. The
+song's protagonist as an assembly of solids instead of an outline, so its
+silhouette CHANGES as the shot moves rather than merely rotating. Recipe in
+`MIGRATION.md`, including the two guards that keep many instances affordable.
+
+Three scenes carry it — Effigy, Floating Geometry, Swarm — which is 34.8% of
+videos containing at least one, against 11.9% when only Effigy had it. That is
+reach, not payoff.
+
+The payoff is still unmeasured: the variety report has not been re-run against
+a library with these in it, so nothing here says the videos are more varied.
+What is measured is narrower — across four seeds, the lit area of Effigy's
+subject varies 14-113% over one turn against Soloist's 3-51% for the same
+rotation, which says the outline genuinely changes rather than merely spinning.
+Whether that reaches the variety blocks is the open question, and it is the next
+thing to run. Do not migrate a field scene onto it hoping for a win.
+
 ### 2. Let the song decide element SIZE
 
 `stageScale()`. Not the size of your features relative to each other — the size