motion-doctrine

قانون حرکت پیوسته برای ساخت ویدیوهایی که مثل یک دوربین واحد پیش می‌روند.

این اسکیل پیش از ساخت هر انیمیشن یا ویدیوی HyperFrames، منطق حرکت بین صحنه‌ها را تعیین می‌کند؛ از جهت، محور و سرعت ورود و خروج تا carrier، حرکت علّی و لحظه مناسب برش. با آن، صحنه‌ها به‌جای اسلایدهای جداگانه، بخشی از یک حرکت دوربین و روایت یکپارچه می‌شوند.

همچنین برای حفظ حرکت معنادار درون صحنه، حذف idle wobble، زمان‌بندی سکون پیش از اوج و انتخاب مسیرهای sustained motion راهنمایی می‌دهد. با ساخت ledger.json و اجرای Seam Gate، خطاهای رایج مانند crossfade، ورود از حالت سکون، ناسازگاری Z و هم‌پوشانی فریم‌ها پیش از رندر شناسایی می‌شوند.

چه چیزی می‌گیرید

• طراحی Vector Ledger برای تمام seamهای بین صحنه‌ها
• قواعد هماهنگ‌سازی محور، جهت، سرعت و علامت scale در ورود و خروج
• انتخاب carrier، حرکت علّی و مسیر مناسب برای حفظ اجرای پیوسته صحنه
• راهنمای حذف idle wobble و جایگزینی آن با staged reveals، camera travel یا UI life
• دستورهای اجرای `seam-stamp.mjs` و `seam-gate.mjs` برای بررسی ساختاری seamها

برای چه کاری خوب است

• ساخت ویدیوهای چندصحنه‌ای HyperFrames با روایت پیوسته و حرکت دوربین‌مانند
• پروژه‌هایی که seam، transition، zoom یا handoff بین عناصر در آن‌ها اهمیت دارد
• ویدیوهای product demo، explainer و launch که باید در تمام فریم‌ها حرکت هدفمند داشته باشند

برای چه کاری نیست

• انیمیشن‌های تک‌صحنه‌ای که seam یا انتقال بین صحنه‌ها ندارند
• پروژه‌هایی که عمداً به crossfade، حرکت تزئینی یا idle wobble متکی هستند
• پیاده‌سازی جزئیات تکنیکی transition؛ برای آن باید به اسکیل‌های implementation مانند `cut-the-curve` رجوع کرد

دربارهٔ این اسکیل

Motion Doctrine (Gateway)

Read this before composing any animation. It decides WHAT happens at every seam and how
every scene performs; the technique skills implement it. These rules supersede generic /
upstream motion guidance. The failure this prevents: scenes authored in isolation — the
eye's momentum dies at every cut, and scenes wobble in place between entry and exit.

Route map

Authoring order: **vector ledger (ledger.json) → STAMP the master seams from it
(scripts/seam-stamp.mjs --ledger ledger.json --write index.html) → sustained-motion
route per phase → carriers and causes → build comps → VERIFY (scripts/seam-gate.mjs).**
Hand-author only Tier-A morphs/match-cuts; stamped seams pass the gate by construction.

Part 1 — The Seam Law

The Vector Law

How Scene A exits determines how Scene B enters: same axis, same direction, matched
speed, cut mid-motion on both sides.

1. Axis — x stays x, y stays y, Z stays Z. Never trade axes across a cut.
2. Direction — never mirror. On Z, direction = the SIGN of scale change: growing = push (camera forward), shrinking = pull (camera back). A receding exit answered by a grow-from-small entry is a mirrored vector — the most common violation, because grow-from-small is the default element entrance.
3. Speed — entry initial velocity ≈ exit final velocity, via mirrored eases (exit power4.in + entry power4.out, same distance and duration; the incoming side picks up ≥50% through the notional path). Mechanics in cut-the-curve.
4. Phase — the cut lands mid-motion on BOTH sides. Settling to rest before the cut, or starting from rest after it, is a dead beat.

The Current

Every film picks ONE dominant direction (house default: LEFT). Every ordinary seam uses
it. Other vectors are RESERVED — spending one means something:

• Never run consecutive seams in opposing directions — ping-pong reads as an error.
• A direction change needs a visible cause (click / bounce / impact) or a chapter boundary.

The Vector Ledger

Write it before authoring any master timeline — as ledger.json at the project root
(schema: references/seam-gate.md). One row per seam: cut time, exit and entry vectors
(axis + signed direction; Z rows carry the scale sign), selectors, technique. Exit and
entry must match; if a row mismatches, fix the plan, not the easing. The verifier checks
row consistency statically before any runtime sampling.

Carriers

The eye follows objects, not abstractions. The strongest seams hand a concrete carrier
across the cut at matched position AND velocity: a cursor mid-path, a container that
shrinks/docks into the next layout, a mark that flies into its exact slot, the word group
of a waterfall cut. With no natural carrier, the scene heroes carry it (partial travel +
early fade, entry mid-flight). Never a crossfade — it has no carrier at all.

Causal Motion

Chain motion so each move is visibly launched by the last: click → squash → release
spring → flight → impact → recoil → reveal.

• Effects start ON the causing frame — same timeline position, never "shortly after."
• Reactions scale with implied mass: big elements rebound slower, small ones snap.
• A force is a license to change direction; an uncaused flip is a ping-pong.

The Seam Gate (build gate — run the verifier, exit 0 or the seam is not done)

node <SKILL_DIR>/scripts/seam-stamp.mjs --ledger ledger.json --write index.html  # generate
node <SKILL_DIR>/scripts/seam-gate.mjs  verify --ledger ledger.json --project .  # verify

The script (usage + ledger schema: references/seam-gate.md) numerically enforces, per
seam: ledger-row consistency, exit still moving at the cut, entry mid-flight (never from
rest), measured direction = ledger direction, entry/exit speed match (WARN), **zero
overlap (one side visible per frame — the cut is not a dissolve), the Z sign** rule
(d(scale)/dt same sign both sides; the incoming scene's own entrances are scanned for
sign-fighting), and carrier rect continuity with ancestor scale included. Use
seam-gate.mjs probe --t <cut> to find each seam's true carrier selectors when authoring
the ledger.

Rules the script cannot check — still yours:

1. Edits re-open the seam. Any change to a scene's first/last ~1s (including re-timing to new VO) invalidates that boundary's audit — re-run the verifier.
2. Audio is the clock. Re-time scenes to the VO's real word timestamps; never rush a read to fit a slot. A VO regen re-opens its seams.
3. Clip-gating gotcha (the usual cause of a zero-overlap FAIL): a clip whose data-start precedes its entry tween is un-hidden at its initial opacity — set initial autoAlpha: 0 AND data-start = the cut time, never earlier.

Part 2 — Performance (the scene keeps performing)

No idle wobble

Idle sine loops (breathe, float, drift, glow pulse) are BANNED as sustained motion — they
read as "the video is waiting." A scene that finishes entering with seconds left is a
planning bug: add story, not wobble. Every phase between entry and exit is owned by one
of these routes (name the route in the plan):

Test: pause at any second — something meaningful must be mid-flight (a reveal landing,
the camera traveling, the UI doing what the narration says).

Stillness before climax

Schedule a 0.3–0.75s pause between the major action and its result — the dramatic
comma. A scene that jumps straight from action to result loses it.

Timing intents

• Single entry ≤ ~800ms; longer buildup = multi-element stagger, not one slow element.
• Exit ≈ 75% of entry. Exception: cut-the-curve inverts this (entry ~127% of exit).
• Total stagger ≤ 500ms; with 8+ elements, tighten per-item delay or stagger the first few.
• Forbidden eases: bounce.out / elastic.out. Entry overshoot back.out(1.4–1.7) is fine.
• Similar elements share one ease+duration intent — never a unique pair per element.

Transition vocabulary

Use only 2–3 inter-scene transitions per film and repeat them; the default boundary is
cut-the-curve in the current's direction. Hand-written shared-element morphs
(intent: morph) don't count against the budget.

Anti-Patterns

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