Agent skill · design visual · heygen-com
seam-craft
Render-correctness doctrine for scene-to-scene seams in HyperFrames launch videos — the prerequisites that make transitions composite correctly on the master timeline. Load when assembling the master timeline / index.html, when a white flash appears at a cut or crossfade seam (especially on dark films), when reasoning about why a transition opacity dip shows through, or when verifying the render-side mechanics of how overlapping scene wrappers blend. Covers the opaque stage-ground (#root background) white-flash guard and how the injector overlaps wrappers, holds final frames, ping-pongs tracks, and stamps lint-clean template code onto the master timeline. Does NOT contain the per-transition catalog — see the transition registry for individual transition entries.
Why this skill is useful
Provides detailed domain-specific knowledge on rendering transitions that the AI wouldn't reliably generate on its own.
What it needs
About 2k tokens when loaded. Last updated 2026-08-07. 39,818 stars on the source repository.
What this skill does
Seam Craft — render prerequisites for scene-to-scene transitions This is the render-correctness doctrine for PLV scene-to-scene seams: the prerequisites and master-timeline mechanics that make any transition composite correctly, independent of which specific transition is chosen. The per-transition catalog (crossfade, push-slide, zoom-through, cut-the-curve, …) lives in the transition registry — this page is the doctrine that sits underneath all of them. The transitions this doctrine governs are Tier-B-ready: pure transform / opacity / filter on the two scene clip wrappers (#el-<sid>), no injected overlay DOM, no per-scene cooperation. Overlay families (staggered blocks, blinds, light leak, grid dissolve, page burn) and shader transitions are deferred to later phases. Stage ground prerequisite (white-flash guard) Several templates open a window where the two wrappers' summed opacity < 1 (the cut-the-curve mid-window cut, zoom-through's 0.15 floor, plain crossfade's power-curve dip). Whatever is BEHIND the wrappers shows through during that window. If the assembled index.html #root has no opaque background, the renderer composites the dip over its default white page → a white flash at every seam, glaring on dark films (observed on two Spotify runs before the fix). The assembler must paint the stage: #root { background: var(--canvas-deep, var(--canvas, #000)) } — assemble-index.mjs now emits this; any other consumer of these templates owns the same guarantee. How the injector applies a transition At a break boundary between scene i (from) and scene i+1 (to), the injector: 1. Extends #el-<from> wrapper data-duration by durations (holds its final frame — verified: core/src/runtime/init.ts:1393-1410 external-slot branch). 2. Pulls #el-<to> wrapper data-start earlier by durations (creates the overlap window). 3. …
How to use it
Reference it in AdaL, Claude Code, Cursor or any coding agent — nothing to install:
@skills heygen-com/seam-craft--7b00ea