Files
hyperframes/docs/catalog/components/slit-scan-reveal.mdx
T
Miguel ÁngelandMiguel Angel Simon Sierra 1ae2067b8d feat(catalog): put the variables panel back, on payloads (#3199)
* feat(catalog): put the variables panel back, on payloads

The panel drove its preview by loading an .html from docs/public, a type the
host does not publish, so it showed an empty frame in production and was
parked when the catalog was re-landed.

It now mounts the same JSON payload the plain player uses and re-mounts it as
values change, injecting them as window.__hfVariables into the composition head
before any of its scripts run, which is where the runtime reads overrides from.
Doing it in the markup rather than after load is what stops the composition
initialising with the wrong values first.

172 items with variables get the panel back; the playhead carries across a
change so a tweak mid-shot does not jump back to frame zero.

* fix(docs): drop the unused url form and the needless escapes

* fix(docs): the panel cannot reference a binding beside the export

* feat(catalog): make importing an SVG the obvious move

A reader arrives at this control with a shape, not with path data, and the
panel asked for the coordinates first. Import is now the primary action in a
drop target you can see is a drop target, and the raw path sits behind a
disclosure for anyone who wants it.

* feat(cli): let a fruitless catalog search report the gap

An agent that searches by meaning and finds nothing worth installing knows
something we do not: the name of a move the catalog is missing. There was no
way to tell us, so that knowledge was lost at the end of every run.

hyperframes feedback --search-miss "<query>" --wanted "<the move>" records it.
It carries no rating, so it never lands in the rating metric, and it is a
separate deliberate command rather than something catalog --query does on its
own: plain search still sends nothing, which is what the CLI promises.

--rating stops being required at the arg level, since a miss has no rating to
give. The check moved into the run body, where an absent one is now handled
rather than crashing on undefined.

* feat(cli): carry tuned variable values into the install snippet

Someone who tunes a block on its catalog page had no way to keep those values:
the install command was the same one everybody gets, and the tuning stayed on
the page.

hyperframes add <item> --vars '<json>' now prints a mount element carrying
data-variable-values, so the values land where the block is used.

They ride on the host rather than being written into the installed file. That
keeps the composition on disk byte-identical to the registry's, so a later
reinstall can still tell an edit from an update, and it lets two mounts of the
same block carry different values.

* fix(catalog): serve the item's own directory so runtime paths resolve

Some compositions assemble their asset URLs at run time —
"compositions/components/" + texture + ".png" for the texture masks, a font the
compiler pulled into _remote_media — and no scan of the markup can see a string
that does not exist until a script concatenates it. Those items either rendered
black or were dropped to a video that had never been uploaded.

Each item that needs it now has its prepared directory published, and its
payload carries a <base> pointing at it, so any relative path the composition
invents resolves. caption-texture renders its masks again, and
variable-font-flex has a preview at all for the first time: its MP4 and poster
are both 403.

Both layouts are published, because which one a composition asks for differs
per item, and a directory only earns that if it is under 2 MB. The 12 MB
texture sheet keeps the recorded video it already had.

* fix(catalog): let the variables panel actually drive the composition

Every control on the panel was inert. The values reached the composition and
nothing repainted, because the payload had already been compiled: compiling
inlines a mounted component and resolves its variables into the markup and CSS,
so by the time a reader turns a knob there is nothing left to change.

An item that declares variables now ships uncompiled, keeping the mount the
runtime loads at run time, which is the only state where data-variable-values
still means anything. The component travels inline as a data URI rather than a
sibling file, because .html is the one type the docs host will not publish. The
demo's own pinned values come off, so the reader's choices reach the mount
instead of losing to the values the demo picked to show itself off.

Measured on the rendered frame rather than the DOM: green rgb(98,207,144),
blue rgb(6,6,199), violet rgb(177,147,230), and back to green.

docs/public/catalog drops from 48 MB to 35 MB along the way, since an
uncompiled payload carries far less than an inlined one.

* feat(catalog): keep variable changes in the url

A reader who tuned a piece lost it on reload, and had nothing to send anyone.
The values now live in the query string, scoped by composition id so two links
never read each other,and only the ones that differ from the defaults are
written, so changing one knob gives a short URL rather than every variable
spelled out.

replaceState rather than pushState: dragging a slider should not leave a trail
of history entries. An unreadable value is ignored rather than thrown, so a
truncated or hand-edited link opens the piece at its defaults.

* fix(catalog): only rewrite the url when a value actually changed

* refactor(catalog): memoise the declared defaults on their content

* feat(catalog): offer an install command carrying the tuned values

The Install block is generated before anyone touches a knob, so it can only
ever print the plain command. Someone who spent a minute tuning a piece copied
it and got the defaults back.

The panel now carries its own command in the Snippet tab, with --vars holding
exactly the values that differ. An untouched piece still offers the same short
command, so nothing gets noisier for the common case.

* fix(catalog): a piece with nothing to render is a skip, not a failure

caption-blend-difference is a stylesheet and a paragraph of prose — a class you
add to your own captions, with no standalone scene to show. The generator
treated that as a build failure, so every run ended by reporting something
broken when nothing was.

It now reports the shape it is and keeps its recorded video, which is the only
honest preview such an item has. A genuine render failure still throws.

* fix(catalog): restore variables from the url on a cold load

A shared link opened at the defaults. The first render happens on the server,
where there is no window to read the query string from, and React then hydrates
against that markup and never revisits it — so the values only appeared once you
touched a control.

The URL is read again after mount, which is the first moment it exists. The
value is also escaped once now rather than twice: URLSearchParams already
decodes on the way out, and decoding a second time turned an SVG path full of
percent-escapes into something that no longer parsed, besides doubling the
length of every link.

* fix(catalog): mount the preview with the values a link carried

The frame was built from the declared defaults and the shared values were
posted to it afterwards, which is too late for anything the composition reads
once at init: a path arrived after the mark had already been drawn from the
default one, so a link looked right in the panel and wrong on screen.

* feat(catalog): the install command follows the values you tuned

Copying the Install line gave the plain command back, because that block is
generated before anyone touches a knob and had no way to know what changed. The
tuned command only existed in the panel Snippet tab, which is not where anyone
looks for it.

The line now reads the same query string the panel writes, so the two agree
without either component knowing the other exists, and a shared link carries the
right command too. replaceState fires no event, so the panel announces its own
writes.

* fix(catalog): send a text variable to the preview once it is finished

Every other control in the explorer reports a whole value on every event: a
slider at any position is a position, a swatch is a colour. A text field is
not. Typing v3 into a badge posted v first, so the preview remounted and
rendered a composition built from half a word.

The post now waits while a text field has focus and goes out when the edit is
committed, with Enter or by clicking away. The field itself is unchanged and
still tracks every keystroke.

---------

Co-authored-by: Miguel Angel Simon Sierra <miguelangelsi07@gmail.com>
2026-08-10 22:40:01 -04:00

740 lines
33 KiB
Plaintext

---
title: "Slit Scan Reveal"
description: "The frame's rows sample an authored subject at offset times: a canvas painter draws row slices of one pure position function evaluated at t minus offset(row), smearing arrival through time until the offsets collapse to zero and the mark holds coherent."
---
import { InstallCommand } from "/snippets/install-command.jsx";
import { VariablesExplorer } from "/snippets/variables-explorer.jsx";
<VariablesExplorer
previewSrc="/public/catalog/components/slit-scan-reveal.json"
compositionId="slit-scan-reveal"
compositionSrc="compositions/components/slit-scan-reveal.html"
variables={[{"id":"axis","type":"enum","role":"style","label":"Axis","description":"rows smears arrival across horizontal slices; cols across vertical slices.","default":"rows","options":[{"value":"rows","label":"Rows"},{"value":"cols","label":"Columns"}]},{"id":"spread","type":"number","role":"timing","label":"Spread","description":"Maximum sampling offset in seconds across the frame; larger smears further through time.","default":0.45},{"id":"resolve_at","type":"number","role":"timing","label":"Resolve at","description":"Seconds from mount start when the offsets start collapsing to zero. Clamped so the collapse and any exit stay inside the clip.","default":2.2},{"id":"accent","type":"enum","role":"style","label":"Accent","description":"Subject ring and orbit color: green rides --brand, blue rides --accent, violet rides --accent-2.","default":"green","options":[{"value":"green","label":"Green"},{"value":"blue","label":"Blue"},{"value":"violet","label":"Violet"}]},{"id":"exit","type":"enum","role":"timing","label":"Exit","description":"Optional departure. Default none: the resolved mark holds until the frame cuts.","default":"none","options":[{"value":"none","label":"None"},{"value":"fade","label":"Fade"},{"value":"up","label":"Up"}]}]}
>
```html slit-scan-reveal.html
<!doctype html>
<!--
slit-scan-reveal: HyperFrames video primitive (time)
The frame's rows sample the subject at offset times. The subject is an
authored token mark (an accent-ringed disc with an orbit dot) whose
motion is one pure position function pos(t): it sweeps in from the wing
on a decaying sine bob and rests dead-center. A canvas painter draws the
frame as row (or column) slices, slice i showing the subject's state at
t - offset(i): arrival smears through time, near bands leading, far
bands trailing. On the resolve cue the offsets collapse to zero with one
eased pass, the smear zips shut, and the subject holds coherent.
Variables (declared in data-composition-variables below):
- axis ("rows" | "cols"): horizontal row slices or vertical column
slices.
- spread (seconds): the maximum sampling offset across the frame.
- resolve_at (seconds): when the offsets start collapsing to zero
(0.6s eased collapse). Clamped so the collapse and any exit stay
inside the clip.
- accent ("green" | "blue" | "violet"): green rides --brand, blue
rides --accent, violet rides --accent-2.
- exit ("none" | "fade" | "up", default none): frame roots own
transitions; the default holds the resolved mark to the last pixel.
Envelope, fixed IN and OUT with elastic HOLD only (never timeScale):
the subject's travel and the collapse are authored against the cues;
HOLD = D - (resolve end) - OUT, truly still (after the collapse every
slice samples the same resting state, so repaints are identical).
OUT_BASE = 0.45s only when exit != none.
Determinism (canvas 2D law): per-slice offset jitter comes from one
table computed once during synchronous timeline construction from fixed
LCG seed 0x51175c4e. Every painted frame is a pure
function of (that table, the timeline's current time): the timeline's
onUpdate clears the canvas and, for every slice, clips to the slice band
and redraws the whole subject at its sampled time from scratch. pos(t)
is closed-form (cubic ease + integer sine cycles that end at zero), so
any sampled time is exact. No Math.random, no wall clock, no
incremental state: eventful seeks repaint identically in any order and
either direction.
Mount contract: the runtime clones only this template. #root fills the
host box (no data-width/data-height, container-type: size, cqmin units),
is styled via #root only, and registers one paused timeline under the
LITERAL "slit-scan-reveal" key. All DOM state is set with explicit
endpoints (gsap.set + fromTo) so any seek order lands identical frames.
-->
<html
lang="en"
data-composition-id="slit-scan-reveal"
data-composition-duration="4"
data-composition-variables='[
{ "id": "axis", "type": "enum", "role": "style", "label": "Axis", "description": "rows smears arrival across horizontal slices; cols across vertical slices.", "default": "rows", "options": [{ "value": "rows", "label": "Rows" }, { "value": "cols", "label": "Columns" }] },
{ "id": "spread", "type": "number", "role": "timing", "label": "Spread", "description": "Maximum sampling offset in seconds across the frame; larger smears further through time.", "default": 0.45 },
{ "id": "resolve_at", "type": "number", "role": "timing", "label": "Resolve at", "description": "Seconds from mount start when the offsets start collapsing to zero. Clamped so the collapse and any exit stay inside the clip.", "default": 2.2 },
{ "id": "accent", "type": "enum", "role": "style", "label": "Accent", "description": "Subject ring and orbit color: green rides --brand, blue rides --accent, violet rides --accent-2.", "default": "green", "options": [{ "value": "green", "label": "Green" }, { "value": "blue", "label": "Blue" }, { "value": "violet", "label": "Violet" }] },
{ "id": "exit", "type": "enum", "role": "timing", "label": "Exit", "description": "Optional departure. Default none: the resolved mark holds until the frame cuts.", "default": "none", "options": [{ "value": "none", "label": "None" }, { "value": "fade", "label": "Fade" }, { "value": "up", "label": "Up" }] }
]'
>
<head>
<meta charset="UTF-8" />
<title>Slit Scan Reveal</title>
</head>
<body>
<template>
<div id="root" data-composition-id="slit-scan-reveal" data-duration="4" data-fps="30">
<style>
*,
*::before,
*::after {
box-sizing: border-box;
}
#root {
position: absolute;
inset: 0;
overflow: hidden;
container-type: size;
isolation: isolate;
color: var(--fg, #f8fafc);
font-family: var(--font-display, "Inter", system-ui, sans-serif);
pointer-events: none;
}
.ssr-clip {
position: absolute;
inset: 0;
overflow: hidden;
background: var(--bg, transparent);
}
.ssr-stage {
position: absolute;
inset: 0;
will-change: transform, opacity;
}
.ssr-canvas {
position: absolute;
inset: 0;
width: 100%;
height: 100%;
}
</style>
<div
id="slit-scan-reveal-clip"
class="ssr-clip clip"
data-start="0"
data-duration="4"
data-track-index="0"
>
<div class="ssr-stage">
<canvas class="ssr-canvas" aria-hidden="true"></canvas>
</div>
</div>
<script src="https://cdn.jsdelivr.net/npm/gsap@3.14.2/dist/gsap.min.js"></script>
<script>
(function () {
"use strict";
var root = document.getElementById("root");
var stage = root.querySelector(".ssr-stage");
var canvas = root.querySelector(".ssr-canvas");
var vars =
window.__hyperframes && window.__hyperframes.getVariables
? window.__hyperframes.getVariables()
: {};
var axis = vars.axis === "cols" ? "cols" : "rows";
var spreadRaw = parseFloat(vars.spread);
var spread = isFinite(spreadRaw) ? Math.min(Math.max(0.1, spreadRaw), 1.2) : 0.45;
var resolveRaw = parseFloat(vars.resolve_at);
var accentColors = {
green: "var(--brand, #71f5a7)",
blue: "var(--accent, #61a8ff)",
violet: "var(--accent-2, #c5a3ff)",
};
var accent = Object.prototype.hasOwnProperty.call(accentColors, vars.accent)
? vars.accent
: "green";
var exit = vars.exit === "fade" || vars.exit === "up" ? vars.exit : "none";
// Envelope. The collapse is 0.6s; resolve_at is clamped so the
// collapse and any exit always fit inside the clip.
var duration = Math.max(0.001, parseFloat(root.dataset.duration || "4"));
var OUT = exit === "none" ? 0 : 0.45;
var COLLAPSE = 0.6;
var resolveAt = isFinite(resolveRaw) ? resolveRaw : 2.2;
resolveAt = Math.min(
Math.max(0.4, resolveAt),
Math.max(0.4, duration - COLLAPSE - OUT - 0.1),
);
// The subject's travel ends just before the collapse begins so
// the zip-shut lands on a resting subject.
var MOVE_START = 0.25;
var MOVE_END = Math.max(MOVE_START + 0.6, resolveAt - 0.1);
var OUT_START = duration - OUT;
// Canvas raster basis, fixed once at mount (elastic root).
var dpr = Math.min(2, Math.max(1, Number(window.devicePixelRatio) || 1));
var box = root.getBoundingClientRect();
var cssW = Math.max(1, Math.round(box.width) || 640);
var cssH = Math.max(1, Math.round(box.height) || 360);
canvas.width = Math.round(cssW * dpr);
canvas.height = Math.round(cssH * dpr);
var ctx = canvas.getContext("2d");
var minDim = Math.min(canvas.width, canvas.height);
// Resolve tokens to concrete colors once at mount so canvas
// fills never depend on style recalc during seeks.
var hostDoc = root.ownerDocument;
function resolveColor(cssColor, fallback) {
var probe = hostDoc.createElement("span");
probe.style.color = cssColor;
root.appendChild(probe);
var value = getComputedStyle(probe).color || fallback;
probe.remove();
return value;
}
var accentColor = resolveColor(accentColors[accent], "#71f5a7");
var surfaceColor = resolveColor("var(--surface, #14171c)", "#14171c");
var fgColor = resolveColor("var(--fg, #f8fafc)", "#f8fafc");
// Seeded per-slice offset jitter: a stable table, computed once.
var SLICES = 96;
var jitter = (function () {
var state = 0x51175c4e;
function next() {
state = (Math.imul(1664525, state) + 1013904223) >>> 0;
return state / 4294967296;
}
var rows = [];
for (var i = 0; i < SLICES; i += 1) {
rows.push(0.96 + 0.08 * next());
}
return rows;
})();
function clamp01(v) {
return v < 0 ? 0 : v > 1 ? 1 : v;
}
// The subject's authored motion: ONE pure position function.
// Cubic-eased sweep from the wing to dead center with a
// decaying two-cycle sine bob (integer cycles, exactly zero at
// u = 1) and a settling scale. The sweep runs ACROSS the slice
// axis (rows: left wing in, cols: top wing down) so every band
// cuts the travel and the offsets read as a staircase smear,
// not a local skew. Defined for every t; clamped flat outside
// [MOVE_START, MOVE_END], so sampled times before mount or
// into the hold are exact and still.
function subjectState(t) {
var u = clamp01((t - MOVE_START) / (MOVE_END - MOVE_START));
var e = 1 - Math.pow(1 - u, 3);
var decay = (1 - u) * (1 - u);
var travel = -0.16 + 0.66 * e;
var bob = 0.5 + 0.15 * Math.sin(Math.PI * 2 * 2 * u) * decay;
return {
x: (axis === "rows" ? travel : bob) * canvas.width,
y: (axis === "rows" ? bob : travel) * canvas.height,
rot: 0.5 * Math.sin(Math.PI * 2 * u) * decay,
scale: 0.82 + 0.18 * e,
appear: clamp01(u / 0.12),
};
}
// Draw the whole subject (token disc + accent ring + orbit dot)
// at one sampled state. Callers clip to a slice band first.
function drawSubject(s) {
if (s.appear <= 0) return;
var r = 0.15 * minDim * s.scale;
ctx.save();
ctx.translate(s.x, s.y);
ctx.rotate(s.rot);
ctx.globalAlpha = s.appear;
// Disc body.
ctx.fillStyle = surfaceColor;
ctx.beginPath();
ctx.arc(0, 0, r, 0, Math.PI * 2);
ctx.fill();
// Accent ring.
ctx.strokeStyle = accentColor;
ctx.lineWidth = Math.max(1, 0.016 * minDim);
ctx.beginPath();
ctx.arc(0, 0, r, 0, Math.PI * 2);
ctx.stroke();
// Inner core.
ctx.fillStyle = fgColor;
ctx.globalAlpha = s.appear * 0.92;
ctx.beginPath();
ctx.arc(0, 0, r * 0.3, 0, Math.PI * 2);
ctx.fill();
// Orbit dot: the asymmetry that makes the smear legible.
ctx.fillStyle = accentColor;
ctx.globalAlpha = s.appear;
ctx.beginPath();
ctx.arc(r * 0.72, 0, r * 0.13, 0, Math.PI * 2);
ctx.fill();
ctx.restore();
}
// Pure repaint: for every slice, clip to its band and draw the
// subject at t - offset(slice) * collapse(t).
function paint(t) {
ctx.clearRect(0, 0, canvas.width, canvas.height);
var collapse = 1 - clamp01((t - resolveAt) / COLLAPSE);
// Eased collapse: smooth both ends (power2.inOut shape).
collapse =
collapse < 0.5 ? 2 * collapse * collapse : 1 - Math.pow(-2 * collapse + 2, 2) / 2;
if (collapse <= 0) {
// Resolved: one coherent draw, no per-slice clipping.
drawSubject(subjectState(t));
return;
}
var along = axis === "rows" ? canvas.height : canvas.width;
var band = along / SLICES;
for (var i = 0; i < SLICES; i += 1) {
var frac = i / (SLICES - 1);
var offset = spread * frac * jitter[i] * collapse;
var s = subjectState(t - offset);
if (s.appear <= 0) continue;
ctx.save();
ctx.beginPath();
if (axis === "rows") {
ctx.rect(0, i * band, canvas.width, band + 1);
} else {
ctx.rect(i * band, 0, band + 1, canvas.height);
}
ctx.clip();
drawSubject(s);
ctx.restore();
}
}
gsap.set(stage, { opacity: 1, y: "0cqh" });
var tl = gsap.timeline({
paused: true,
onUpdate: function () {
paint(tl.time());
},
});
// Anchor tween: an inert plain-object tween spanning the full
// authored duration so tl.time() covers [0, D] and onUpdate
// repaints the canvas on every eventful seek.
tl.to({ p: 0 }, { p: 1, duration: duration, ease: "none" }, 0);
// HOLD: truly still. After the collapse every slice samples the
// same resting state, so the canvas repaints one coherent mark.
// OUT: optional departure; exit none holds until the frame cuts.
if (exit === "up") {
tl.to(stage, { y: "-4cqh", duration: OUT, ease: "power2.in" }, OUT_START);
tl.to(stage, { opacity: 0, duration: OUT, ease: "power2.in" }, OUT_START);
} else if (exit === "fade") {
tl.to(stage, { opacity: 0, duration: OUT, ease: "power2.in" }, OUT_START);
}
tl.seek(0);
paint(0);
window.__timelines = window.__timelines || {};
window.__timelines["slit-scan-reveal"] = tl;
})();
</script>
</div>
</template>
</body>
</html>
```
</VariablesExplorer>
## Install
<InstallCommand command="npx hyperframes add slit-scan-reveal" item="slit-scan-reveal" />
That writes one file: `compositions/components/slit-scan-reveal.html`.
## Paste it into your composition
Open `compositions/components/slit-scan-reveal.html` and copy what is inside into your own composition.
A component has no size or duration of its own. It takes both from the composition
you paste it into.
## Variables
Every one of these has a default, so the piece works untouched. Set the ones you
want to change on the element:
| Variable | Default | Accepts | What it does |
| --- | --- | --- | --- |
| `axis` | `rows` | `rows`, `cols` | rows smears arrival across horizontal slices; cols across vertical slices. |
| `spread` | `0.45` | number | Maximum sampling offset in seconds across the frame; larger smears further through time. |
| `resolve_at` | `2.2` | number | Seconds from mount start when the offsets start collapsing to zero. Clamped so the collapse and any exit stay inside the clip. |
| `accent` | `green` | `green`, `blue`, `violet` | Subject ring and orbit color: green rides --brand, blue rides --accent, violet rides --accent-2. |
| `exit` | `none` | `none`, `fade`, `up` | Optional departure. Default none: the resolved mark holds until the frame cuts. |
Set them with `data-variable-values` on the element that mounts it. These are the
defaults, so this behaves exactly like the preview above until you change one:
```html wrap
<div
data-composition-id="slit-scan-reveal"
data-composition-src="compositions/components/slit-scan-reveal.html"
data-variable-values='{"axis":"rows","spread":0.45,"resolve_at":2.2,"accent":"green","exit":"none"}'
></div>
```
## Source
<Accordion title={`slit-scan-reveal.html`}>
```html
<!doctype html>
<!--
slit-scan-reveal: HyperFrames video primitive (time)
The frame's rows sample the subject at offset times. The subject is an
authored token mark (an accent-ringed disc with an orbit dot) whose
motion is one pure position function pos(t): it sweeps in from the wing
on a decaying sine bob and rests dead-center. A canvas painter draws the
frame as row (or column) slices, slice i showing the subject's state at
t - offset(i): arrival smears through time, near bands leading, far
bands trailing. On the resolve cue the offsets collapse to zero with one
eased pass, the smear zips shut, and the subject holds coherent.
Variables (declared in data-composition-variables below):
- axis ("rows" | "cols"): horizontal row slices or vertical column
slices.
- spread (seconds): the maximum sampling offset across the frame.
- resolve_at (seconds): when the offsets start collapsing to zero
(0.6s eased collapse). Clamped so the collapse and any exit stay
inside the clip.
- accent ("green" | "blue" | "violet"): green rides --brand, blue
rides --accent, violet rides --accent-2.
- exit ("none" | "fade" | "up", default none): frame roots own
transitions; the default holds the resolved mark to the last pixel.
Envelope, fixed IN and OUT with elastic HOLD only (never timeScale):
the subject's travel and the collapse are authored against the cues;
HOLD = D - (resolve end) - OUT, truly still (after the collapse every
slice samples the same resting state, so repaints are identical).
OUT_BASE = 0.45s only when exit != none.
Determinism (canvas 2D law): per-slice offset jitter comes from one
table computed once during synchronous timeline construction from fixed
LCG seed 0x51175c4e. Every painted frame is a pure
function of (that table, the timeline's current time): the timeline's
onUpdate clears the canvas and, for every slice, clips to the slice band
and redraws the whole subject at its sampled time from scratch. pos(t)
is closed-form (cubic ease + integer sine cycles that end at zero), so
any sampled time is exact. No Math.random, no wall clock, no
incremental state: eventful seeks repaint identically in any order and
either direction.
Mount contract: the runtime clones only this template. #root fills the
host box (no data-width/data-height, container-type: size, cqmin units),
is styled via #root only, and registers one paused timeline under the
LITERAL "slit-scan-reveal" key. All DOM state is set with explicit
endpoints (gsap.set + fromTo) so any seek order lands identical frames.
-->
<html
lang="en"
data-composition-id="slit-scan-reveal"
data-composition-duration="4"
data-composition-variables='[
{ "id": "axis", "type": "enum", "role": "style", "label": "Axis", "description": "rows smears arrival across horizontal slices; cols across vertical slices.", "default": "rows", "options": [{ "value": "rows", "label": "Rows" }, { "value": "cols", "label": "Columns" }] },
{ "id": "spread", "type": "number", "role": "timing", "label": "Spread", "description": "Maximum sampling offset in seconds across the frame; larger smears further through time.", "default": 0.45 },
{ "id": "resolve_at", "type": "number", "role": "timing", "label": "Resolve at", "description": "Seconds from mount start when the offsets start collapsing to zero. Clamped so the collapse and any exit stay inside the clip.", "default": 2.2 },
{ "id": "accent", "type": "enum", "role": "style", "label": "Accent", "description": "Subject ring and orbit color: green rides --brand, blue rides --accent, violet rides --accent-2.", "default": "green", "options": [{ "value": "green", "label": "Green" }, { "value": "blue", "label": "Blue" }, { "value": "violet", "label": "Violet" }] },
{ "id": "exit", "type": "enum", "role": "timing", "label": "Exit", "description": "Optional departure. Default none: the resolved mark holds until the frame cuts.", "default": "none", "options": [{ "value": "none", "label": "None" }, { "value": "fade", "label": "Fade" }, { "value": "up", "label": "Up" }] }
]'
>
<head>
<meta charset="UTF-8" />
<title>Slit Scan Reveal</title>
</head>
<body>
<template>
<div id="root" data-composition-id="slit-scan-reveal" data-duration="4" data-fps="30">
<style>
*,
*::before,
*::after {
box-sizing: border-box;
}
#root {
position: absolute;
inset: 0;
overflow: hidden;
container-type: size;
isolation: isolate;
color: var(--fg, #f8fafc);
font-family: var(--font-display, "Inter", system-ui, sans-serif);
pointer-events: none;
}
.ssr-clip {
position: absolute;
inset: 0;
overflow: hidden;
background: var(--bg, transparent);
}
.ssr-stage {
position: absolute;
inset: 0;
will-change: transform, opacity;
}
.ssr-canvas {
position: absolute;
inset: 0;
width: 100%;
height: 100%;
}
</style>
<div
id="slit-scan-reveal-clip"
class="ssr-clip clip"
data-start="0"
data-duration="4"
data-track-index="0"
>
<div class="ssr-stage">
<canvas class="ssr-canvas" aria-hidden="true"></canvas>
</div>
</div>
<script src="https://cdn.jsdelivr.net/npm/gsap@3.14.2/dist/gsap.min.js"></script>
<script>
(function () {
"use strict";
var root = document.getElementById("root");
var stage = root.querySelector(".ssr-stage");
var canvas = root.querySelector(".ssr-canvas");
var vars =
window.__hyperframes && window.__hyperframes.getVariables
? window.__hyperframes.getVariables()
: {};
var axis = vars.axis === "cols" ? "cols" : "rows";
var spreadRaw = parseFloat(vars.spread);
var spread = isFinite(spreadRaw) ? Math.min(Math.max(0.1, spreadRaw), 1.2) : 0.45;
var resolveRaw = parseFloat(vars.resolve_at);
var accentColors = {
green: "var(--brand, #71f5a7)",
blue: "var(--accent, #61a8ff)",
violet: "var(--accent-2, #c5a3ff)",
};
var accent = Object.prototype.hasOwnProperty.call(accentColors, vars.accent)
? vars.accent
: "green";
var exit = vars.exit === "fade" || vars.exit === "up" ? vars.exit : "none";
// Envelope. The collapse is 0.6s; resolve_at is clamped so the
// collapse and any exit always fit inside the clip.
var duration = Math.max(0.001, parseFloat(root.dataset.duration || "4"));
var OUT = exit === "none" ? 0 : 0.45;
var COLLAPSE = 0.6;
var resolveAt = isFinite(resolveRaw) ? resolveRaw : 2.2;
resolveAt = Math.min(
Math.max(0.4, resolveAt),
Math.max(0.4, duration - COLLAPSE - OUT - 0.1),
);
// The subject's travel ends just before the collapse begins so
// the zip-shut lands on a resting subject.
var MOVE_START = 0.25;
var MOVE_END = Math.max(MOVE_START + 0.6, resolveAt - 0.1);
var OUT_START = duration - OUT;
// Canvas raster basis, fixed once at mount (elastic root).
var dpr = Math.min(2, Math.max(1, Number(window.devicePixelRatio) || 1));
var box = root.getBoundingClientRect();
var cssW = Math.max(1, Math.round(box.width) || 640);
var cssH = Math.max(1, Math.round(box.height) || 360);
canvas.width = Math.round(cssW * dpr);
canvas.height = Math.round(cssH * dpr);
var ctx = canvas.getContext("2d");
var minDim = Math.min(canvas.width, canvas.height);
// Resolve tokens to concrete colors once at mount so canvas
// fills never depend on style recalc during seeks.
var hostDoc = root.ownerDocument;
function resolveColor(cssColor, fallback) {
var probe = hostDoc.createElement("span");
probe.style.color = cssColor;
root.appendChild(probe);
var value = getComputedStyle(probe).color || fallback;
probe.remove();
return value;
}
var accentColor = resolveColor(accentColors[accent], "#71f5a7");
var surfaceColor = resolveColor("var(--surface, #14171c)", "#14171c");
var fgColor = resolveColor("var(--fg, #f8fafc)", "#f8fafc");
// Seeded per-slice offset jitter: a stable table, computed once.
var SLICES = 96;
var jitter = (function () {
var state = 0x51175c4e;
function next() {
state = (Math.imul(1664525, state) + 1013904223) >>> 0;
return state / 4294967296;
}
var rows = [];
for (var i = 0; i < SLICES; i += 1) {
rows.push(0.96 + 0.08 * next());
}
return rows;
})();
function clamp01(v) {
return v < 0 ? 0 : v > 1 ? 1 : v;
}
// The subject's authored motion: ONE pure position function.
// Cubic-eased sweep from the wing to dead center with a
// decaying two-cycle sine bob (integer cycles, exactly zero at
// u = 1) and a settling scale. The sweep runs ACROSS the slice
// axis (rows: left wing in, cols: top wing down) so every band
// cuts the travel and the offsets read as a staircase smear,
// not a local skew. Defined for every t; clamped flat outside
// [MOVE_START, MOVE_END], so sampled times before mount or
// into the hold are exact and still.
function subjectState(t) {
var u = clamp01((t - MOVE_START) / (MOVE_END - MOVE_START));
var e = 1 - Math.pow(1 - u, 3);
var decay = (1 - u) * (1 - u);
var travel = -0.16 + 0.66 * e;
var bob = 0.5 + 0.15 * Math.sin(Math.PI * 2 * 2 * u) * decay;
return {
x: (axis === "rows" ? travel : bob) * canvas.width,
y: (axis === "rows" ? bob : travel) * canvas.height,
rot: 0.5 * Math.sin(Math.PI * 2 * u) * decay,
scale: 0.82 + 0.18 * e,
appear: clamp01(u / 0.12),
};
}
// Draw the whole subject (token disc + accent ring + orbit dot)
// at one sampled state. Callers clip to a slice band first.
function drawSubject(s) {
if (s.appear <= 0) return;
var r = 0.15 * minDim * s.scale;
ctx.save();
ctx.translate(s.x, s.y);
ctx.rotate(s.rot);
ctx.globalAlpha = s.appear;
// Disc body.
ctx.fillStyle = surfaceColor;
ctx.beginPath();
ctx.arc(0, 0, r, 0, Math.PI * 2);
ctx.fill();
// Accent ring.
ctx.strokeStyle = accentColor;
ctx.lineWidth = Math.max(1, 0.016 * minDim);
ctx.beginPath();
ctx.arc(0, 0, r, 0, Math.PI * 2);
ctx.stroke();
// Inner core.
ctx.fillStyle = fgColor;
ctx.globalAlpha = s.appear * 0.92;
ctx.beginPath();
ctx.arc(0, 0, r * 0.3, 0, Math.PI * 2);
ctx.fill();
// Orbit dot: the asymmetry that makes the smear legible.
ctx.fillStyle = accentColor;
ctx.globalAlpha = s.appear;
ctx.beginPath();
ctx.arc(r * 0.72, 0, r * 0.13, 0, Math.PI * 2);
ctx.fill();
ctx.restore();
}
// Pure repaint: for every slice, clip to its band and draw the
// subject at t - offset(slice) * collapse(t).
function paint(t) {
ctx.clearRect(0, 0, canvas.width, canvas.height);
var collapse = 1 - clamp01((t - resolveAt) / COLLAPSE);
// Eased collapse: smooth both ends (power2.inOut shape).
collapse =
collapse < 0.5 ? 2 * collapse * collapse : 1 - Math.pow(-2 * collapse + 2, 2) / 2;
if (collapse <= 0) {
// Resolved: one coherent draw, no per-slice clipping.
drawSubject(subjectState(t));
return;
}
var along = axis === "rows" ? canvas.height : canvas.width;
var band = along / SLICES;
for (var i = 0; i < SLICES; i += 1) {
var frac = i / (SLICES - 1);
var offset = spread * frac * jitter[i] * collapse;
var s = subjectState(t - offset);
if (s.appear <= 0) continue;
ctx.save();
ctx.beginPath();
if (axis === "rows") {
ctx.rect(0, i * band, canvas.width, band + 1);
} else {
ctx.rect(i * band, 0, band + 1, canvas.height);
}
ctx.clip();
drawSubject(s);
ctx.restore();
}
}
gsap.set(stage, { opacity: 1, y: "0cqh" });
var tl = gsap.timeline({
paused: true,
onUpdate: function () {
paint(tl.time());
},
});
// Anchor tween: an inert plain-object tween spanning the full
// authored duration so tl.time() covers [0, D] and onUpdate
// repaints the canvas on every eventful seek.
tl.to({ p: 0 }, { p: 1, duration: duration, ease: "none" }, 0);
// HOLD: truly still. After the collapse every slice samples the
// same resting state, so the canvas repaints one coherent mark.
// OUT: optional departure; exit none holds until the frame cuts.
if (exit === "up") {
tl.to(stage, { y: "-4cqh", duration: OUT, ease: "power2.in" }, OUT_START);
tl.to(stage, { opacity: 0, duration: OUT, ease: "power2.in" }, OUT_START);
} else if (exit === "fade") {
tl.to(stage, { opacity: 0, duration: OUT, ease: "power2.in" }, OUT_START);
}
tl.seek(0);
paint(0);
window.__timelines = window.__timelines || {};
window.__timelines["slit-scan-reveal"] = tl;
})();
</script>
</div>
</template>
</body>
</html>
```
</Accordion>
{/* hf:generated-footer */}
Tagged `motion-primitive` `time` `slit-scan` `canvas` `deterministic` `experiment`.
## Related topics
- [Browse the complete Catalog](/catalog)
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