# REPORT — 04-line-art · ATELIER LINEA / 一线万象

## Concept (two sentences)
A single unbroken champagne-gold line draws a whole story on a midnight ground:
a seed becomes a sapling, the sapling's branch dives off the crown and *becomes*
a building's structure, the building walks into a skyline, the skyline lifts off
its last tower and loops into a monogram, and the monogram's outline fills with
gold to become a solid mark while the wordmark rises. The camera rides the pen
tip the whole way, then dollies out to reveal one composed poster — a luxury /
architecture identity film in which every figure is literally the next figure's
first stroke.

## Beat sheet (timecodes)
| t (s) | beat | what happens |
|---|---|---|
| 0.00 | hook | tip ignites with a one-shot flare; drawing begins immediately (never a blank beat) |
| 0.05–0.60 | seed | a closed gold lens is drawn from its tip; the pen returns to the seed's apex |
| 0.60–1.15 | stem | the stem grows straight up out of the seed |
| 1.15–1.72 | leaves | right leaf loop, short stem, left leaf loop |
| 2.10–2.72 | crown + dive | the crown bends right and *dives* to the city baseline — the branch becomes the first structural line |
| 2.72–3.80 | tower A | left pier rises, a comb of hanging fins builds the façade, right pier falls to the baseline |
| 3.80–4.50 | tower B | a shorter finned mass continues the walk |
| 4.50–5.30 | skyline | seven thin flat-topped towers walk right |
| 5.30–6.28 | the lift | the line rolls off the last tower, climbs the right margin and arcs back over the rooftops |
| 6.28–6.86 | ring | the lift settles into the medallion's lower-right vertex and the pen closes a full circle |
| 6.86–7.20 | the A | the ring keeps the pen; it draws a tall isoceles "A" inscribed in the circle, then lays the crossbar |
| **7.20–7.82** | **HERO — line to fill** | the glyph's outline fills with gold, flooding radially from the pen's anchor; the crossbar is revealed as a knockout so the mark reads as an "A" |
| 7.85–8.55 | wordmark | "ATELIER LINEA" rises with settling letter-spacing; 「一线万象」 follows |
| 8.55–10.00 | hold | composed end frame with living micro-motion (line boil, medallion glow, slow camera drift) |

## How each signature feature is realised on screen
- **以单色细线为唯一造型语言 / one monochrome hairline is the only drawing
  language** — there is exactly one path object in the film (`PATH`), stroked at
  a constant 3 px screen width with round caps and round joins. No fills exist
  until the hero moment.
- **描边生长 draw-on from the tip** — implemented with real arc-length, not a
  dash trick: the polyline carries a cumulative-length table, and each frame
  draws "the path up to arc distance s(t)". A soft glowing pen tip leads the
  draw and the ~150-unit run behind it is re-stroked bright with a shadow glow.
- **一笔画：上一图形的尾线即下一图形的起线** — guaranteed by construction: the
  figures are appended to one point list, so the last point of each figure *is*
  the first point of the next. There is no cut anywhere in the film; the branch
  that dives off the sapling is the same stroke that becomes the building's
  rising pier.
- **线宽全片恒定 2–4 px, round caps** — 3 px, `lineCap/lineJoin = round`, for all
  300 frames regardless of the camera scale (sense of scale comes from the
  virtual camera, never from stroke weight).
- **转角处描绘减速, cubic-bezier(0.65,0,0.35,1)** — every figure is drawn with
  `EASE.inOut` (that exact control-point curve) over its own time window, so the
  pen decelerates into every junction and every roof corner.
- **线转面 line-to-fill from the anchor** — at 7.20 s the inscribed glyph fills
  with a champagne-gold radial flood whose front emanates from the pen's last
  anchor point; the crossbar survives as a deep-ground knockout, revealed by the
  same front, so the mark resolves into an "A".
- **大量负空间 / minimal luxury** — the poster keeps ~10 % side margins and large
  top/bottom negative space; the ground is flat `#0B1320` with a very subtle
  centre lift, a vignette and coarse film grain (~3 px cells, low amount, a few
  px/s drift — coarse and light so H.264 stays ~6.6 Mbps instead of boiling).
- **端点手绘感 / subtle boil** — from 8.35 s a 0.95 px deterministic value-noise
  boil fades in over the whole drawing, sampled on a continuously advancing index
  so the held lines breathe rather than re-randomise.
- **结尾活体定格 / living end hold** — the composed poster is the calmest part of
  the film but never dead: the whole drawing floats on a slow desynchronised
  sway/bob, the medallion pulses and breathes a soft halo, the lines shimmer, and
  a constant-velocity gallery-light rake travels the frame so no window bottoms
  out at a sine apex (rhythm: 2.7 % / 0.88 % / 0.74 % moved across the hold).
- **虚拟相机跟笔 / virtual camera** — a 4-value camera (scale + world centre) is
  key-framed to the tip and read from the same cue times as the picture; it
  holds ~4.2× on the seed, ~1.3× through the city and dollies out to 1.1× for
  the poster.
- **older segments dim to ~35 %** — every figure keeps its own brightness and
  settles from 1.0 to 0.34 over ~0.7 s once the camera moves on.

## Tech route
A web page that can draw any `t` on demand (harness contract:
`window.__ready` / `window.renderAt(t)`), captured frame-by-frame in headless
Chrome and encoded with ffmpeg.

- `parts/geometry.mjs` — builds the one continuous path from hand-authored
  Béziers and arcs, flattens it to a ~3,900-point polyline and stores cumulative
  arc length.
- `parts/film.mjs` — the renderer: camera, per-figure reveal, pen tip, glow,
  the fill, the type, bloom / vignette / grain. Everything is a pure function of
  `t`; all step functions use `smooth`/`EASE`; the only randomness is a seeded
  `mulberry32` for the grain tile.
- `audio.py` — one cue sheet drives both picture and sound: felt piano, four
  string chord blocks (D–Bm–G–D), a pen-on-paper whisper whose gain tracks each
  figure's tip speed, structural sub hits as the city rises, a whoosh on the
  lift, and a delicate bell chime on the fill.

## Check numbers (from `out/04-line-art/qa.json`)
- duration **10.000 s**, **1920×1080**, **30 fps** (h264, yuv420p), **8.3 MB / 6.6 Mbps**
- audio **AAC 48 kHz stereo**, integrated **−13.9 LUFS**, true peak **−5.6 dBTP**
- **0 black frames**, **5 near-static frames** of 299 scanned, **0 console errors**
- `harness/audit.mjs` verdict **ok — 0 dead spans** (was 3 dead spans before the
  end-hold fix); full render: 300 frames at ~0.54 s/frame, no PROBLEMS line

## Honest top-3 weaknesses
1. **The city reads as a comb.** The finned façades and the flat-topped skyline
   are drawn as one continuous "n" walk, which is the honest one-line solution
   but gives the skyline a bar-chart regularity; a stronger version would carve
   setback roofs, a spire and a couple of horizontal floors into the same stroke.
2. **The lift arches over the right-hand skyline and encloses it**, which reads
   slightly as a frame/loop rather than a pure "horizon lifting". Given that the
   mark sits left of the skyline, the stroke has to pass over or under it; the
   side it takes is a compromise.
3. **The mark is a solid gold triangle with a bar.** It clearly resolves to an
   "A" and the ring makes it a seal, but a triangle is still a common shape and
   the mark leans on the wordmark to be unambiguous; a bespoke ligature would be
   braver.

## Self-scores (1–10; 6 = template, 8 = high-end agency, 9 = award shortlist)
| axis | score | note |
|---|---|---|
| style fidelity | 9 | one hairline, real drawn-on arc-length, constant width, line-to-fill, 一笔画 continuity — an expert names the style in one second |
| concept | 8 | seed→sapling→structure→skyline→mark is a genuine one-line narrative, not decoration; the mark itself is the weakest link |
| motion craft | 8 | eased draws, deceleration into corners, camera lead, element-carried transitions; fewer squashes than a fuller toolkit would allow |
| design & typography | 8 | strong grid, real negative space, Didot + Songti pairing, correct CJK punctuation; the skyline's regularity is the soft spot |
| finish & texture | 8 | controlled palette, bloom, vignette, deterministic grain, no banding or shimmer |
| sound & sync | 8 | one cue sheet shared by picture and sound, whisper tracks tip speed, chime lands on the fill; the score is deliberately sparse |
| technical | 9 | exact 10.000 s, clean console, 0 black/frozen frames, within loudness and true-peak spec, deterministic |

**Overall: 8.3 — high-end agency level; the shortest path to a 9 is a bespoke
monogram and a less regular skyline.**