Two helpers made the bulk of it mechanical. `inkStroke` is a drop-in for
sigEdge — the same line at the identity's weight rather than the track's — and
`castForm` is a drop-in for sigForm, same signature so call sites do not change
shape. With those in place the substitution table is one-to-one:
sigForm( -> castForm( sigShape( -> castMain( sigEdge( -> inkStroke(
Forty-seven scenes went through that pass in one run: twenty-six take the cast
and the ink, twenty-one take the ink alone. Then the gate ran over all sixty-five
and found three the pass had broken, which is the entire reason it exists.
Spectrum Sculpture rendered pure black. It had been using sigShape as a RADIAL
METRIC rather than drawing it, and the cast carries notches and a hollow — an
annulus used as a radius turns a sculpture inside out. Reverted to sigShape and
dropped to ink only. The lesson generalises: a scene that reads a form as
geometry is not a scene that draws it, and the classifier cannot tell those
apart from the source.
Eclipse Field stopped honouring its `style` trait. It opts out of surface grain,
so sigEdge was its only style evidence, and the ink replaced it. The trait claim
is now dropped — and so is the lint change that had let inkMask count as style
evidence, which was wrong and was hiding exactly this. A trait is a property of
the track a scene may honour; an artifact is content it draws. Taking the ink
says nothing about whether a scene responds to u_sigLine.
Circuit Bloom went empty at the bottom of its `grown` range, where the pads were
carried by a hairline and the ink's stroke is thinner than the edge it replaced.
Now filled as well as stroked.
Also: the backtick check now covers every shader literal rather than only the
preamble, because a mechanical pass over sixty files reintroduced one
immediately. Three rounds lost to that typo is enough.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
The cast and ink slice lowered the floor as predicted but left `scale` — feature
size — consistently WORSE than the legacy arm, 0.033 against 0.053 and well
outside the noise. Every stage still chose its own element size from its own
param range, so every song landed in the same place: the videos shared a cast
and also, accidentally, shared how big everything was.
Staging is the third artifact. A lattice — grid, radial, spiral, scatter,
strata — with jitter, spread, a size hierarchy and a bias toward the middle or
the edges, transported the same way the cast is: uniforms plus a `stageNode`
function in the preamble, no new engine plumbing. Constellation, Swarm and
Procession place on it; the stage keeps its motion and gives up its composition.
Soloist takes only the scale, since a close-up has no composition to share.
`elementScale` is the part that mattered. It is the song's answer to "how big is
this made of", spanning about a factor of six, and it is the decision that was
missing rather than mis-set. Measured, over twelve songs and three runs:
stages spread +0.0111 ±0.0043 → +0.0143 ±0.0008
scale block 0.033 ±0.004 → 0.041 ±0.007
Against the legacy arm at +0.0108 ±0.0071 the harness still says
indistinguishable, and it is right to: the gap is +0.0035 and the legacy arm's
own run-to-run range is twice that. What can be said is narrower and holds up.
Stages have the lowest floor of the three arms by a clear margin — 0.082 against
0.095 and 0.104 — so sharing content does make a video look like itself, which
was the central prediction. And the targeted fix moved the block it was aimed at
in the direction it was aimed.
Also added: a lint check that the shader preamble contains no backticks. Twice
now one has closed the template literal and produced a check page that hangs on
"starting…" with an empty console, which is an expensive way to find a typo.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Four stages, an identity layer, and an A/B that says the idea is right and the
reason it works is not the reason I expected.
A stage has no image of its own. It owns arrangement — a procession, a
constellation, a soloist, a swarm — and what it arranges comes from the track:
`castMain` and `castChorus` for the forms, `inkMask` and `inkValue` for the hand
they are drawn in. The identity generates a protagonist and a chorus with sides,
notches and hollows, plus an ink treatment of weight, edge, fill, outline and
posterisation. All of it travels as uniforms, so it is data rather than code and
a stage consumes it without knowing any other stage exists.
The protagonist IS the signature form rather than a second opinion about it.
They were separate draws in the first version, which let a track built on
hexagons put a round protagonist on screen — the signature said one thing and
the picture said another, and the shape trait stopped meaning anything for
stages. The cast now reads its geometry from the personality live and adds the
notches and hollows that turn a shape into a character.
Measured across seven songs, three arms, same instrument:
arm floor observed spread
stages, four of them 0.0801 0.1133 +0.0332
legacy scenes, four of them 0.0830 0.1122 +0.0292
the unrestricted generator 0.1058 0.1146 +0.0088
The prediction in EPIC-3 §7 was that sharing a cast would drop the floor
sharply. The floor did drop sharply — by a quarter — but nearly all of that came
from casting FEWER scenes per video, not from sharing content: the legacy arm,
four ordinary scenes with no cast at all, gets most of the same benefit. Stages
add about 14% on top of that.
That is worth knowing before building the other four registers. The single
largest available win was hiding in the roster size all along, and it costs one
number to take.
One result runs the wrong way and is recorded rather than explained: coupling is
+0.29 on the legacy arm and -0.18 on the stages. At twenty-one pairs neither is
distinguishable from zero, so it is a flag for a larger sample rather than a
finding.
Also fixed: a backtick inside the shader preamble's template literal, which
closed it and made every check page hang on "starting…" with no error in the
console.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Revisiting the framing layer turned up that it was not reaching four of the
forty-two scenes, and that none of its gates could have told us.
Those gates check the PLAN — cue sizes, the distribution of shot sizes across
a population, headroom, seek determinism — and a plan that never reaches the
image passes every one of them. Rendered at wide, normal and close, Scan
Tear, Pylon Grid, Pitch Shatter and the 3D Particle Field came back
byte-identical at every size.
The cause was a category error in the first implementation. Framing was
applied inside sigCamera, which is gated on the `camera` personality trait —
so a scene that declined the track's drift and sway silently declined the
shot size as well. That gating is right for a TRAIT and wrong for framing,
which is not one: framing is where the camera is standing for this shot, and
no scene should be exempt from it because of an unrelated art-direction
decision.
- Framing now lives in the shader epilogue, applied to the coordinate every
fragment scene is handed, so honouring it is not optional. uv is left
unframed on purpose: it is screen space, and prev() and sigGrain belong to
the output image rather than to the scene being filmed.
- Scan Tear and Pitch Shatter build their image from uv deliberately — a
signal artefact happens to the signal, not to the world behind it. They now
slice on raw uv and build the field they displace from a new framedUv(p),
so the tear stays locked to the frame while the imagery behind it is filmed
wide or close.
- Particle Field receives framing in update() and honours it as a camera
dolly, which is what framing literally is when a layer has a real camera.
Distance divided by scale, matching the fragment path where the coordinate
is divided by it.
New gate renders instead of inspecting: 42 of 42 scenes now respond to
framing, weakest Ridge Terrain at 0.22 of its own brightness, against a 0.05
floor. Also drops a stale comment on Layer.setFraming that still claimed
sigCamera applied it.
105/105 checks pass including the slow set.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Both phases come out of the manual gate — watching whole tracks — and both
fix something no automated check was looking for.
Phase 8: shots. A section is a STAGE of the song and can run ninety
seconds; one scene held that long reads as a still image with a wobble on
it. Each section kind now gets a roster of three or four stage visuals
instead of one scene, and each section is cut into shots that rotate
between them on phrase lines, never holding past 22s. The roster stays per
kind, so a track's drops still cut between the same images and the video
keeps its identity; the anchor opens each section and the rotation returns
to it, and when a companion is due it is the least recently shown one.
The arc driver stopped working in sections and started working in cues, one
per shot, so a shot cut and a section change take the same code path and
differ only in transition length. The default transition is a slow
dissolve — two bars calm, one loud; a straight cut is reserved for
sections above the energy threshold, because on calm material a cut reads
as a glitch rather than as an edit.
Phase 9: production design. With cuts every fifteen seconds the next
problem was that the images being cut between shared nothing but the
palette. What a music video actually shares across shots is a location, a
cast, a camera operator and an art direction, so each track now generates a
personality in four traits (shape, camera, space, style) off the look seed.
The traits reach shaders as uniforms plus four helpers in the contract, and
each scene expresses them its own way: Classic Wave's rings take the
signature polygon, Metaballs merge as one, Floating Geometry no longer
picks between a box and a circle because the production already decided.
The part that makes it a design rather than a filter: scenes DECLARE which
traits they honour, a track is built on one or two, and a scene that does
not honour all of them is not cast in that track. The library shrinks per
track on purpose.
Two gates keep the declaration honest — lint greps each shader for evidence
of every trait it claims, and a render check measures that each declared
trait actually moves the image (41 scene/trait pairs, weakest response 64
of 255). A layer with no personality renders bit-identically to before,
which is what keeps every earlier sweep and regression valid.
Checks changed rather than added:
- P4 scene-change and drift checks now measure per shot, not per section;
the crossfade check reads its length off the cue.
- P5 flash sweep runs per shot, so the visuals that only appear
mid-section are measured too.
- P6 preview/export parity primes first (as both real paths do) and
compares at the one-LSB tolerance Phase 7 already uses. Measured over
four consecutive shows: 3 frames at delta 1, then bit-exact — GPU
variance on first render, not a divergence.
- P2's contract-uniform list is derived from the contract instead of
retyped, so the signature uniforms cannot fall out of sync.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Engine core: Timeline (fixed dt, audio-mastered in realtime), seeded Rng,
Renderer, Layer/ShaderLayer/SceneLayer, Compositor with blend modes,
feedback and post chain.
Shader scenes are compiled against a fixed uniform contract and define only
`vec4 scene(vec2 uv, vec2 p)`, so adding a scene costs a shader plus a
params block. Deep Nebula ported from party-stage as the first one.
Gate passes, 7/7 in checks.html:
- 300 frames rendered twice are bit-identical
- a fresh Engine reproduces the same frames
- simulated dropped frames change nothing (proves dt is fixed)
- seek matches sequential playback
- 320x180 vs 1280x720 agree within 0.010 (limit 0.06)
- seeded rng reproducible, forked streams independent
- compositor reset clears feedback history
Static gates: no wall-clock or unseeded randomness in deterministic
directories; scene schemas and shader sources agree in both directions.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
