chantier: dynamic videos — wave 3

[LeadcodeDev]

Tracking issue for the dynamic-videos chantier (2026-07-19): 3D transforms, glassmorphism, camera zooms, organic motion — from the targeted audit (3 phantoms confirmed: transform origins, motion-path, 3D adaptive shadows; zombie fields; missing focal/parallax/per-element grain).

Execution plan (merges on user signal only)

PR 1 — foundations (single branch, 3 issues)

• feat(engine): real transform-origin and perspective-origin #86 real transform-origin / perspective-origin — in PR
• feat(engine): complete the glassmorphism kit #87 complete glassmorphism kit — in PR
• feat(engine): spring easing on any animation preset #88 spring easing on any preset — in PR

PR 2 — cinematic camera

• feat(engine): camera focal point (zoom-to origin) #89 camera focal point
• feat(engine): multi-plane camera parallax via element depth #90 multi-plane parallax via element depth

PR 3+ — organic & 3D polish

• feat(engine): parameterized organic drift preset + true simplex noise #91 drift preset + true simplex
• feat(engine): implement motion-path #92 motion-path
• feat(engine): 3D depth sorting (opt-in) and backface-visibility #93 3D depth sorting + backface-visibility
• feat(engine): 3D adaptive shadows (or fix the doc) #94 3D adaptive shadows (implement or fix doc)

Final deliverable

• examples/dynamic-glass.json — 15s showcase example exercising the wave: 3D perspectives with configurable origins (hinge rotations), full glassmorphism kit (backdrop-filter + noise grain + gradient-border), spring presets, camera focal zoom + parallax if PR 2 lands first. Built with the rustmotion skill flow (validate + still-by-still visual QA + render), own PR, merge on user signal.

Decision log

• PRs grouped by overlapping files (paint_pass shared by feat(engine): real transform-origin and perspective-origin #86/feat(engine): complete the glassmorphism kit #87) since merges now await the user's signal — granular issues, batched merges.
• Studio PR feat(studio+components): typed enum fields, palette-prefilled colors, string lists #85 (inspector rounds 6-7) still open in parallel; engine branches start from main.