motion-doctrine

The saved excerpt is a snapshot from when this skill was listed. The external source remains the complete and most current version.

---
name: motion-doctrine
description: "GATEWAY — load FIRST before composing any HyperFrames animation or video. The high-level motion law that makes a multi-scene video feel like ONE continuous camera move instead of a stack of independently-animated slides. Covers the vector law (how you exit determines how you enter, incl. the Z scale-sign rule), the film's current, carrier elements, causal motion, the Seam Gate (build-gate enforcement), the ban on idle wobble (motion must PERFORM, not breathe), stillness-before-climax, and the sustained-motion routes. Routes to the low-level technique skills (cut-the-curve — the full catalog incl. waterfall entry + nudge curve, oversized-cursor, seam-craft). These rules SUPERSEDE generic / upstream motion guidance. [continuity, direction, vector, momentum, seam, transition, ease, performance, idle-motion, narrative-motion, film-grammar]"
metadata:
  internal: true
---

# 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

| Decision (this skill)                              | Implementation skill                                                                              |
| -------------------------------------------------- | ------------------------------------------------------------------------------------------------- |
| Seam transition choice + parameters + code         | `cut-the-curve` §1–5 (the catalog)                                                                |
| Text / element entry cascades                      | `cut-the-curve` §6 (waterfall entry)                                                              |
| In-scene group repositioning (no cut)              | `cut-the-curve` §7 (nudge curve)                                                                  |
| Cursor-led action / scene kickoff / morph ignition | `oversized-cursor`                                                                                |
| Seam render mechanics / white-flash guard          | `seam-craft`                                                                                      |
| Product-launch / explainer / caption work          | overlays `text-beat-economics`, `brand-faithful`, `captions-overlay` on top of the upstream skill |

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