cut-the-curve

name cut-the-curve description The technique catalog: five velocity-matched SEAMS (zoom-through, INVERSE zoom-through, cut-the-curve, waterfall cut, rack-focus blur-cut) plus the two in-scene techniques — waterfall ENTRY (staggered arrival cascades for title cards / segment openers) and the nudge curve (slow-fast-slow three-phase group slides). Covers partial-travel (~12% of frame) velocity matching via mirrored power4 eases, the Z scale-sign rule, size-scaled blur (10px text / 18-20px full-frame), word-by-word staggered cuts, cascade pacing by element weight, and the 10/65/25 slide ratio. Read before authoring any transition, text-beat handoff, kinetic text entry, or group reposition. [depth, zoom, inverse-zoom, scale-sign, mirrored-zoom, rack-focus, pacing, velocity, cut-the-curve, waterfall, stagger, cascade, kinetic-text, title-card, segment-opener, nudge, slide, easing, group-motion, z-depth, motion-graphics, cinematic, transition, blur, directional-continuity] Cut the Curve — the technique catalog Five SEAM techniques, one principle: cut at peak velocity, match direction and speed on both sides of the cut — plus the two in-scene techniques (§6 arrivals, §7 slides). The seam LAW — vector law, the current, the ledger, the Seam Gate — lives in motion-doctrine ; read it first. This skill is the parameters and mechanics. All GSAP code templates (worker + registry): examples/gsap-implementation.md . Catalog # Technique Scope Axis Use for 1 Zoom-Through (forward) Within-scene text swap Z, toward viewer progressing deeper into the same thought 2 Inverse Zoom-Through Arrival / payoff beat Z, away from viewer something bigger lands 3 Cut the Curve Between scenes X / Y the default boundary, the film's current 4 Waterfall Cut Text-to-text seam X, per-word word-level handoff between big-text beats 5 Rack-Focus Blur-Cut Same-surface state swap X / Y / Z the one cut you want SEEN — a DSLR focus-pull flourish 6 Waterfall Entry In-scene ARRIVAL (no seam) Y, from below title cards, segment openers, list intros 7 Nudge Curve In-scene group slide (no seam) X / Y repositioning a composed group to make room Z direction is a sign "Same axis" is not enough on Z — the sign of d(scale)/dt must match across the cut: Z vector Exit scale Entry scale Variant Push (forward) growing 1 → 1.2 growing 0.75 → 1 zoom-through Pull (back) shrinking 1 → 0.8 shrinking 1.25 → 1 inverse zoom-through Banned mirrors: a receding exit answered by a grow-from-small entry (pull flips to push — the common one, since grow-from-small is the default element entrance), and a push exit answered by an oversized retraction. This binds the incoming scene's OWN entrances during the seam window (cut + ~0.5s), not just the wrapper tween: hold the incoming frame composed, or author its entrance to match the sign. Verify per Seam Gate rule 7. Blur logic (all Z variants) Subject Peak blur Why Text-scale (headline, word group) 10px 20px smears letterforms — the cut reads as a glitch, not speed Full-frame surface (window, card, screenshot) 18–20px lighter blur on a big surface reads as a rendering hiccup Same peak blur on both sides at the swap frame. Blur the WRAPPER, never children. 1. Zoom-Through (forward) Z-axis velocity-matched cut; never both texts visible. Everything GROWS: the outgoing text accelerates toward camera, a hard swap hides at peak blur, the incoming text keeps growing into the focal plane. Headlines and short phrases only. Total ≈ 0.4s. Phase Scale Blur Opacity Ease Duration Exit 1 → 1.2 0 → 10px 1 → 0.15 power3.in (opacity: separate none tween) 0.2s Cut ( tl.set ) in: 0.75 10px out: 0 / in: 0.15 — — Entry 0.75 → 1 10 → 0px 0.15 → 1 expo.out 0.5s Exit opacity MUST be its own linear tween — power3.in holds opacity near 1 too long. On entry all properties share expo.out . 2. Inverse Zoom-Through (backward) The pull-back mirror: the outgoing element RECEDES; the incoming arrives OVERSIZED (as if just behind camera) and retracts into the focal plane. Everything SHRINKS. Spend on ARRIVAL/payoff beats — a payoff line, a giant reply, a held end-state — never ordinary boundaries. Total ≈ 0.7s (30% exit / 70% entry). Phase Scale Blur Opacity Ease Duration Exit 1 → 0.8 0 → 10px 1 → 0.15 power3.in (opacity: separate none tween) ~0.2s Cut ( tl.set ) in: 1.25 10px out: 0 / in: 0.15 — — Entry 1.25 → 1 10 → 0px 0.15 → 1 expo.out ~0.5s Blur is 10px text-scale; 18–20px only when both sides are full-bleed surfaces. Sign discipline: the incoming scene arrives as a composed frame inside the retracting wrapper — no grow-from-small intro in the seam window. Staged entrances happen after the retraction settles, or start ≥1 and retract. 3. Cut the Curve (default scene boundary) X/Y velocity-matched cut — the default for ALL scene-to-scene boundaries, in the film's current, not an accent. The outgoing hero accelerates in one direction, the cut lands mid-motion, the incoming hero continues the SAME direction and decelerates. Total ≈ 0.6s; directions LEFT / RIGHT / UP / DOWN (default LEFT). Partial travel: ~12% of frame (≈230px at 1920) — never full off-screen moves. Direction Exit Entry start → end Leftward x: 0 → −230 x: +230 → 0 Rightward x: 0 → +230 x: −230 → 0 Upward y: 0 → −230 y: +230 → 0 Downward y: 0 → +230 y: −230 → 0 Mechanics: Mirrored eases: exit power4.in + entry power4.out , same distance and duration — the two halves of one power4.inOut , so velocity matches exactly at the cut. The fade trick: exit opacity completes at ~25–30% of its travel (fade ≈ 0.18–0.3s vs motion 0.3–0.34s); entry ignites at ~0.35 opacity mid-path. Time the last fading element to die right at the cut — a gap where nothing moves reads as dead air. Exit 0.2–0.4s; entry ≥ exit. Optional blur 8–10px. Stage ground: #root must be opaque ( background: var(--canvas-deep, var(--canvas, #000)) ) — the mid-window cut opens a summed-opacity < 1 window that flashes white otherwise (see seam-craft ). push-slide exists but violates partial-travel and mid-motion phase; prefer cut-the-curve. 4. Waterfall Cut (word-by-word cut-the-curve) Cut-the-curve at WORD granularity — the strongest leftward cut for text-to-text seams. Outgoing words ramp out on their own curves; incoming words cascade in mid-flight — a wave the eye rides across the seam. Scope: worker-authored inside one multi-beat comp (stacked full-frame .beat layers), NOT a registry/injector type — it tweens word spans, not clip wrappers. The boundary into and out of the text-beat block still gets a normal registry transition. Does not count against the 2–3 transition budget. Parameter Value Why Travel ±230px (~12% frame) partial travel + velocity > full-frame push Exit 0.34s power4.in the acceleration IS the cut Exit fade 0.18s, starts with x word gone by ~25–30% of travel — no smear Exit stagger +0.022s reading order the line peels, not a block slide Entry 0.3s power4.out back half of the composite — velocity match Entry start opacity 0.35 mid-path ignition; binary 0→1 pops Entry gaps 0.05s × 0.84 decay accelerating cascade, resolves composed Rules: One direction per chain, riding the current. Inverse zoom is the chain's ARRIVAL beat only. Pre-set all words to x: +230, opacity: 0 at build time — immediateRender: false alone leaves un-started words visible at rest. A short first beat may exit whole-line: its fade ends ~0.02s before the cut so it is still streaking when the next words ignite — no dead gap. Transform/opacity only (seek-safe); opaque stage ground applies. 5. Rack-Focus Blur-Cut (the visible cut) The one variant where the cut is SEEN: a defocus blur SPIKE hides a single-frame hard swap — a handheld-DSLR focus-pull. Use as an occasional flourish for a state swap of the SAME surface within one visual theme; never the default boundary. Differences from the others: outgoing stays FULLY OPAQUE until the cut (the blur hides the swap — no early fade); eases power2.in / power2.out (soft optics, not momentum). Rules: Fire only at a narrative beat, ≤ once per ~8s; never mid-caption or during a hold. Cut at PEAK blur (≥6px; peak 8–12px, ≤16–18px max) — swapping on the way up shows the cut. A subtle scale (~1.06 lens-breathing) sells it as optics. Same direction on both sides — the vector law still holds. Entry ≥ exit duration. Blur the wrapper; never blur + opacity in one tween on one element (headless compositing bug); never blur a <video> directly (wrap it). 6. Waterfall Entry (in-scene arrival — not a seam) Staggered ARRIVAL cascade: words/elements whip in from below (one consistent direction), each starting before the previous settles — an accelerating wave that resolves into a composed layout. Title cards, segment openers, list/feature intros. The seam sibling is §4; do not mix their rules: §6 Entry (arrival) §4 Waterfall Cut (seam) Opacity BINARY 0→1 via tl.set at entry — never fade ignites at 0.35 mid-path — the fade IS the velocity trick Axis default Y, from below X, riding the current Outgoing side none words ramp out on mirrored power4.in Choreography: Overlap, don't queue — next element starts within ±2 frames of the previous settling; gaps SHRINK across the cascade; the last element snaps. Velocity varies by weight — heavy/anchor elements travel further and longer; light words/punctuation snap in tight: Parameter Anchor/heavy Normal word Light/punctuation Y offset 60–80px 40–50px 30–48px Duration 0.16–0.20s 0.13–0.16s 0.10–0.13s Overlap 0–2f gap 1f overlap 1–2f overlap Ease power4.out (expo.out for extra snap); never .inOut on an entry. One direction per cascade. Split the FINAL word into fragments to extend the climax; fragments travel further. Post-settle, the group usually slides to make room for the next beat — that's §7. 7. Nudge Curve (in-scene group slide — not a seam) Slow-fast-slow repositioning of a composed group (word rows, card stacks, lists) to reveal content or make room. No single built-in ease produces it — power4.inOut smacks to a stop. Chain three tweens on one property: | Phase | Ease | Distance | Time | Feel |