mirror of
https://github.com/heygen-com/hyperframes.git
synced 2026-09-01 19:42:03 +00:00
Miguel ÁngelandMiguel Angel Simon Sierra
1ae2067b8d
* 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>
1130 lines
44 KiB
Plaintext
1130 lines
44 KiB
Plaintext
---
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title: "Oscilloscope Trace"
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description: "CRT oscilloscope beam sweeping a waveform across a 10x8 graticule, with closed-form phosphor persistence: the tail decays as exp(-age/tau) and brightens where the beam slows"
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---
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import { InstallCommand } from "/snippets/install-command.jsx";
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import { VariablesExplorer } from "/snippets/variables-explorer.jsx";
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<VariablesExplorer
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previewSrc="/public/catalog/blocks/oscilloscope-trace.json"
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compositionId="oscilloscope-trace"
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compositionSrc="compositions/oscilloscope-trace.html"
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variables={[{"id":"waveform","type":"enum","label":"Waveform","default":"sine","options":[{"value":"sine","label":"Sine"},{"value":"square","label":"Square"},{"value":"triangle","label":"Triangle"},{"value":"data","label":"Data series"}]},{"id":"frequency","type":"number","label":"Signal frequency","unit":"Hz","default":12,"min":0.1,"max":200,"step":0.1},{"id":"amplitude","type":"number","label":"Amplitude","unit":"div","default":3,"min":0.1,"max":4,"step":0.1},{"id":"persistenceMs","type":"number","label":"Phosphor persistence (tau)","unit":"ms","default":100,"min":1,"max":1000,"step":1},{"id":"phosphorColor","type":"color","label":"Phosphor colour","default":"#5dff8f"},{"id":"sweepRate","type":"number","label":"Sweep rate","unit":"sweeps/s","default":5,"min":0.25,"max":60,"step":0.25},{"id":"dataSeries","type":"string","label":"Data series (waveform=data)","default":"","placeholder":"0,0.4,0.9,0.3,-0.6,-1,-0.2,0.5"}]}
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>
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```html oscilloscope-trace.html
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<!doctype html>
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<html
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lang="en"
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data-composition-variables='[
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{"id":"waveform","type":"enum","label":"Waveform","default":"sine","options":[{"value":"sine","label":"Sine"},{"value":"square","label":"Square"},{"value":"triangle","label":"Triangle"},{"value":"data","label":"Data series"}]},
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{"id":"frequency","type":"number","label":"Signal frequency","unit":"Hz","default":12,"min":0.1,"max":200,"step":0.1},
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{"id":"amplitude","type":"number","label":"Amplitude","unit":"div","default":3,"min":0.1,"max":4,"step":0.1},
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{"id":"persistenceMs","type":"number","label":"Phosphor persistence (tau)","unit":"ms","default":100,"min":1,"max":1000,"step":1},
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{"id":"phosphorColor","type":"color","label":"Phosphor colour","default":"#5dff8f"},
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{"id":"sweepRate","type":"number","label":"Sweep rate","unit":"sweeps/s","default":5,"min":0.25,"max":60,"step":0.25},
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{"id":"dataSeries","type":"string","label":"Data series (waveform=data)","default":"","placeholder":"0,0.4,0.9,0.3,-0.6,-1,-0.2,0.5"}
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]'
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>
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<head>
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<meta charset="UTF-8" />
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<meta name="viewport" content="width=1920, height=1080" />
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<title>Oscilloscope Trace</title>
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<script src="https://cdn.jsdelivr.net/npm/gsap@3.14.2/dist/gsap.min.js"></script>
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<style>
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* {
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margin: 0;
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padding: 0;
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box-sizing: border-box;
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}
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html,
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body {
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width: 1920px;
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height: 1080px;
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overflow: hidden;
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background: #05070a;
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}
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#os-root {
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position: relative;
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width: 1920px;
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height: 1080px;
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font-family: "JetBrains Mono", ui-monospace, monospace;
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}
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#os-bg {
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position: absolute;
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inset: 0;
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background: radial-gradient(120% 120% at 30% 25%, #0d141b 0%, #05070a 68%);
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}
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#os-screen {
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position: absolute;
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inset: 0;
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width: 1920px;
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height: 1080px;
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display: block;
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}
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/* Purely decorative CRT falloff — no timing, no motion. */
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#os-vignette {
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position: absolute;
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inset: 0;
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pointer-events: none;
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background: radial-gradient(
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78% 78% at 34% 50%,
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rgba(0, 0, 0, 0) 55%,
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rgba(0, 0, 0, 0.55) 100%
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);
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}
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#os-readout {
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position: absolute;
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left: 1250px;
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top: 150px;
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width: 520px;
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color: #6f8794;
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font-size: 26px;
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line-height: 1.15;
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letter-spacing: 0.04em;
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}
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#os-readout .os-title {
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color: #b9ccd6;
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font-size: 34px;
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letter-spacing: 0.22em;
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padding-bottom: 26px;
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border-bottom: 2px solid #1d2a33;
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margin-bottom: 26px;
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}
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#os-readout .os-row {
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display: flex;
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justify-content: space-between;
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padding: 13px 0;
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}
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#os-readout .os-val {
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color: #d7e6ee;
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}
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#os-readout .os-note {
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margin-top: 28px;
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font-size: 20px;
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color: #6a7b85;
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line-height: 1.5;
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}
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</style>
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</head>
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<body>
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<div
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id="os-root"
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data-composition-id="oscilloscope-trace"
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data-start="0"
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data-duration="6"
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data-width="1920"
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data-height="1080"
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>
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<div id="os-bg"></div>
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<canvas
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id="os-screen"
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class="clip"
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width="1920"
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height="1080"
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data-start="0"
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data-duration="6"
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data-track-index="0"
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></canvas>
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<div id="os-vignette"></div>
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<div id="os-readout" class="clip" data-start="0" data-duration="6" data-track-index="1">
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<div class="os-title">OSCILLOSCOPE</div>
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<div class="os-row"><span>SOURCE</span><span class="os-val" id="os-r-wave">SINE</span></div>
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<div class="os-row"><span>FREQ</span><span class="os-val" id="os-r-freq">-</span></div>
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<div class="os-row"><span>TIMEBASE</span><span class="os-val" id="os-r-time">-</span></div>
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<div class="os-row"><span>VERT</span><span class="os-val" id="os-r-amp">-</span></div>
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<div class="os-row"><span>PHOSPHOR</span><span class="os-val" id="os-r-phos">-</span></div>
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<div class="os-note" id="os-r-note"></div>
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</div>
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</div>
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<script>
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(function () {
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"use strict";
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// ---------------------------------------------------------------
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// Oscilloscope trace with phosphor persistence.
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//
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// Two pieces of physical truth drive the look:
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//
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// 1. PERSISTENCE. The phosphor keeps emitting after the beam has
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// passed, decaying as exp(-age/tau). Decay constants by EIA
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// phosphor class (research entry F#10):
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// P11/P31 - 0.01-1 ms (what a real bench scope uses: no
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// visible afterglow at video rates)
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// P1 - 80-150 ms (the "vintage glow" look; tau ~= 100 ms
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// is the entry's recommended default)
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// P33 - > 1 s
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// P2/P7 - 30 s .. ~1 min (radar territory, out of range here)
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// The tail window is 3*tau: after three time constants ~5% of the
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// brightness remains, which the entry gives as the safe cutoff.
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//
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// 2. BEAM-VELOCITY BRIGHTNESS. A trace is brighter where the beam
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// moves slower, because the same deposited energy is spread over
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// a shorter path. Each sub-step deposits a fixed amount of energy
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// (constant dt), so surface brightness goes as 1/segment-length.
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// Flat parts of the waveform are bright; fast vertical edges are
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// faint. Qualitative law only - the research entry states it with
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// no proportionality constant, so the reference length below is
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// the physical minimum (pure horizontal sweep motion), not a
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// fudge factor.
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//
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// SWEEP RATE PROVENANCE. The phosphor decay constants above are
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// measured; the sweep rate is NOT - the research entry gives no
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// timebase figure. The default of 5 sweeps/s is authored: across the
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// 10-division graticule it works out to 20 ms/div, a real value from
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// the standard 1-2-5 timebase sequence, picked because it puts a few
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// cycles of the default signal on screen. Treat it as a dial, not as
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// a measurement.
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//
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// NO FEEDBACK BUFFER. The canvas is cleared every frame and the tail
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// is recomputed by evaluating the beam curve backwards in time from
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// the current frame: P(t - k*dt) for k = 0..K. Frame N depends only
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// on N, so seeking anywhere is exact rather than approximate.
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// ---------------------------------------------------------------
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var COMP_ID = "oscilloscope-trace";
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var DURATION = 6;
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// Screen geometry: a 10x8 division graticule of SQUARE divisions,
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// the standard CRT scope face.
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var DIV = 100;
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var DIVS_X = 10;
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var DIVS_Y = 8;
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var SW = DIV * DIVS_X;
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var SH = DIV * DIVS_Y;
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var SX = 140;
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var SY = 140;
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var CY = SY + SH / 2;
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// Tail window in time constants (research entry F#10: 3*tau leaves
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// ~5% weight, stated there as the safe cutoff).
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var TAIL_TAUS = 3;
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// Sub-step count. The entry suggests K ~= 24 steps across the window,
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// which is enough to quantise the DECAY but far too coarse spatially:
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// at 12 Hz the beam would advance 0.15 of a cycle per step and the
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// trace would render as a polygon. So K is derived from how fast the
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// beam actually moves - keep each sub-step under SEG_TARGET_PX of
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// travel. That target and the clamps are MY numbers, not measured
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// ones; the clamp bounds per-frame cost when persistence is long.
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var SEG_TARGET_PX = 3;
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var K_MIN = 120;
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var K_MAX = 8000;
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// Band-limit for the square wave. A real generator + a real scope
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// front end both have finite bandwidth, so the edge is steep but not
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// instantaneous; a mathematical step would make the vertical edge one
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// sub-step long and the velocity law would erase it entirely.
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var SQUARE_SHARPNESS = 8;
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function readVariables() {
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var api = window.__hyperframes && window.__hyperframes.getVariables;
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if (typeof api === "function") return api() || {};
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// Standalone fallback (raw file opened without the runtime): read
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// the same declaration the runtime reads, so defaults have exactly
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// one home.
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var out = {};
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try {
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var raw = document.documentElement.getAttribute("data-composition-variables");
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var decls = JSON.parse(raw || "[]");
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for (var i = 0; i < decls.length; i++) out[decls[i].id] = decls[i].default;
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} catch (err) {
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/* declaration missing or malformed - fall through to hard defaults */
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}
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return out;
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}
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function num(value, fallback, min, max) {
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var n = typeof value === "number" ? value : parseFloat(value);
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if (!isFinite(n)) n = fallback;
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return Math.min(max, Math.max(min, n));
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}
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var V = readVariables();
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var waveform =
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["sine", "square", "triangle", "data"].indexOf(String(V.waveform)) >= 0
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? String(V.waveform)
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: "sine";
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var frequency = num(V.frequency, 12, 0.1, 200);
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var amplitude = num(V.amplitude, 3, 0.1, 4);
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var tau = num(V.persistenceMs, 100, 1, 1000) / 1000;
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var sweepRate = num(V.sweepRate, 5, 0.25, 60);
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var phosphor = parseColor(V.phosphorColor, [93, 255, 143]);
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// waveform="data" replays a supplied series instead of a synthetic
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// shape: comma/whitespace separated numbers, clamped to -1..1, linearly
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// interpolated, one full pass of the series per `frequency` cycle.
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// Empty or unparseable -> falls back to sine.
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var series = String(V.dataSeries == null ? "" : V.dataSeries)
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.split(/[\s,]+/)
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.map(parseFloat)
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.filter(function (n) {
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return isFinite(n);
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})
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.map(function (n) {
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return Math.min(1, Math.max(-1, n));
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});
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if (waveform === "data" && series.length < 2) waveform = "sine";
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function parseColor(value, fallback) {
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var m = /^#?([0-9a-f]{6})$/i.exec(String(value == null ? "" : value).trim());
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if (!m) return fallback;
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var v = parseInt(m[1], 16);
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return [(v >> 16) & 255, (v >> 8) & 255, v & 255];
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}
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function rgba(c, a) {
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return "rgba(" + c[0] + "," + c[1] + "," + c[2] + "," + a.toFixed(4) + ")";
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}
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// --- the signal: pure function of time, no state ------------------
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function wave(t) {
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var p = frequency * t; // cycles elapsed
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if (waveform === "square") {
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return Math.tanh(SQUARE_SHARPNESS * Math.sin(2 * Math.PI * p));
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}
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if (waveform === "triangle") {
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return (2 / Math.PI) * Math.asin(Math.sin(2 * Math.PI * p));
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}
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if (waveform === "data") {
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var frac = p - Math.floor(p);
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var pos = frac * (series.length - 1);
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var i = Math.floor(pos);
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var f = pos - i;
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var a = series[i];
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var b = series[Math.min(series.length - 1, i + 1)];
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return a + (b - a) * f;
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}
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return Math.sin(2 * Math.PI * p);
|
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}
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/** Horizontal sweep position, 0..1 across the graticule. */
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function sweepU(t) {
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var s = t * sweepRate;
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return s - Math.floor(s);
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}
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function beamX(t) {
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return SX + sweepU(t) * SW;
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}
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function beamY(t) {
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return CY - wave(t) * amplitude * DIV;
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}
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// Upper bound on beam speed, in px/s, used to pick the sub-step count.
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// Horizontal is the constant sweep; vertical is the waveform's steepest
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// slope, which differs per shape - a band-limited square is
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// SQUARE_SHARPNESS times steeper at its edge than a sine of the same
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// frequency, and under-sampling exactly there is what turns the edge
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// into a polygon.
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var slopeBound;
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if (waveform === "square") {
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slopeBound = SQUARE_SHARPNESS * 2 * Math.PI * frequency;
|
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} else if (waveform === "triangle") {
|
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slopeBound = 4 * frequency;
|
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} else if (waveform === "data") {
|
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var maxStep = 0;
|
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for (var si = 1; si < series.length; si++) {
|
||
maxStep = Math.max(maxStep, Math.abs(series[si] - series[si - 1]));
|
||
}
|
||
slopeBound = maxStep * (series.length - 1) * frequency;
|
||
} else {
|
||
slopeBound = 2 * Math.PI * frequency;
|
||
}
|
||
var beamSpeedMax = Math.sqrt(
|
||
Math.pow(SW * sweepRate, 2) + Math.pow(slopeBound * amplitude * DIV, 2),
|
||
);
|
||
|
||
// --- graticule (drawn once to an offscreen canvas) ----------------
|
||
|
||
var grat = document.createElement("canvas");
|
||
grat.width = 1920;
|
||
grat.height = 1080;
|
||
(function drawGraticule() {
|
||
var g = grat.getContext("2d");
|
||
g.fillStyle = "#04080a";
|
||
g.fillRect(SX, SY, SW, SH);
|
||
g.strokeStyle = "rgba(120,180,160,0.16)";
|
||
g.lineWidth = 1;
|
||
for (var i = 1; i < DIVS_X; i++) {
|
||
g.beginPath();
|
||
g.moveTo(SX + i * DIV + 0.5, SY);
|
||
g.lineTo(SX + i * DIV + 0.5, SY + SH);
|
||
g.stroke();
|
||
}
|
||
for (var j = 1; j < DIVS_Y; j++) {
|
||
g.beginPath();
|
||
g.moveTo(SX, SY + j * DIV + 0.5);
|
||
g.lineTo(SX + SW, SY + j * DIV + 0.5);
|
||
g.stroke();
|
||
}
|
||
// Centre axes carry the fine 0.2-division ticks, as on a real face.
|
||
g.strokeStyle = "rgba(150,205,185,0.32)";
|
||
var cx = SX + SW / 2 + 0.5;
|
||
var cy = CY + 0.5;
|
||
g.beginPath();
|
||
g.moveTo(cx, SY);
|
||
g.lineTo(cx, SY + SH);
|
||
g.moveTo(SX, cy);
|
||
g.lineTo(SX + SW, cy);
|
||
g.stroke();
|
||
g.strokeStyle = "rgba(150,205,185,0.42)";
|
||
for (var k = 1; k < DIVS_X * 5; k++) {
|
||
var x = SX + (k * DIV) / 5 + 0.5;
|
||
g.beginPath();
|
||
g.moveTo(x, cy - 9);
|
||
g.lineTo(x, cy + 9);
|
||
g.stroke();
|
||
}
|
||
for (var m = 1; m < DIVS_Y * 5; m++) {
|
||
var y = SY + (m * DIV) / 5 + 0.5;
|
||
g.beginPath();
|
||
g.moveTo(cx - 9, y);
|
||
g.lineTo(cx + 9, y);
|
||
g.stroke();
|
||
}
|
||
g.strokeStyle = "rgba(160,215,195,0.55)";
|
||
g.lineWidth = 2;
|
||
g.strokeRect(SX + 1, SY + 1, SW - 2, SH - 2);
|
||
})();
|
||
|
||
// --- per-frame paint ----------------------------------------------
|
||
|
||
var canvas = document.getElementById("os-screen");
|
||
var ctx = canvas.getContext("2d");
|
||
|
||
function draw(t) {
|
||
ctx.globalCompositeOperation = "source-over";
|
||
ctx.clearRect(0, 0, 1920, 1080);
|
||
ctx.drawImage(grat, 0, 0);
|
||
|
||
var windowS = TAIL_TAUS * tau;
|
||
var K = Math.max(
|
||
K_MIN,
|
||
Math.min(K_MAX, Math.round((windowS * beamSpeedMax) / SEG_TARGET_PX)),
|
||
);
|
||
var dt = windowS / K;
|
||
// Length the beam covers in one sub-step with zero vertical motion.
|
||
// That is the slowest the beam can ever move, so it is the maximum
|
||
// brightness reference and the velocity weight never exceeds 1.
|
||
var lRef = SW * sweepRate * dt;
|
||
|
||
ctx.globalCompositeOperation = "lighter";
|
||
ctx.lineCap = "round";
|
||
|
||
// Oldest -> newest, so the bright head lands on top.
|
||
var prevX = 0;
|
||
var prevY = 0;
|
||
var prevU = 0;
|
||
var havePrev = false;
|
||
for (var k = K; k >= 0; k--) {
|
||
var tk = t - k * dt;
|
||
if (tk < 0) {
|
||
// Before frame 0 the beam had not been switched on yet.
|
||
havePrev = false;
|
||
continue;
|
||
}
|
||
var u = sweepU(tk);
|
||
var x = SX + u * SW;
|
||
var y = beamY(tk);
|
||
if (havePrev && u >= prevU) {
|
||
var dx = x - prevX;
|
||
var dy = y - prevY;
|
||
var len = Math.sqrt(dx * dx + dy * dy);
|
||
// Beam-velocity law: brightness ~ 1 / path length per unit time.
|
||
var vel = len > 1e-6 ? Math.min(1, lRef / len) : 1;
|
||
var decay = Math.exp((-k * dt) / tau);
|
||
var a = decay * vel;
|
||
if (a > 0.002) {
|
||
ctx.beginPath();
|
||
ctx.moveTo(prevX, prevY);
|
||
ctx.lineTo(x, y);
|
||
ctx.strokeStyle = rgba(phosphor, a * 0.13);
|
||
ctx.lineWidth = 13;
|
||
ctx.stroke();
|
||
ctx.strokeStyle = rgba(phosphor, a * 0.9);
|
||
ctx.lineWidth = 3;
|
||
ctx.stroke();
|
||
if (a > 0.55) {
|
||
// Overdriven phosphor saturates towards white at the head.
|
||
ctx.strokeStyle =
|
||
"rgba(255,255,255," + (((a - 0.55) / 0.45) * 0.7).toFixed(4) + ")";
|
||
ctx.lineWidth = 1.4;
|
||
ctx.stroke();
|
||
}
|
||
}
|
||
}
|
||
// Retrace is blanked on a real scope: when u wraps, drop the
|
||
// connecting segment instead of drawing a line back across.
|
||
prevX = x;
|
||
prevY = y;
|
||
prevU = u;
|
||
havePrev = true;
|
||
}
|
||
|
||
// Beam head: the spot itself, brightest point on the screen.
|
||
var hx = beamX(t);
|
||
var hy = beamY(t);
|
||
var glow = ctx.createRadialGradient(hx, hy, 0, hx, hy, 22);
|
||
glow.addColorStop(0, "rgba(255,255,255,0.95)");
|
||
glow.addColorStop(0.22, rgba(phosphor, 0.85));
|
||
glow.addColorStop(1, rgba(phosphor, 0));
|
||
ctx.fillStyle = glow;
|
||
ctx.beginPath();
|
||
ctx.arc(hx, hy, 22, 0, Math.PI * 2);
|
||
ctx.fill();
|
||
|
||
ctx.globalCompositeOperation = "source-over";
|
||
}
|
||
|
||
// --- readout --------------------------------------------------------
|
||
|
||
(function fillReadout() {
|
||
// Nearest EIA phosphor class for the chosen tau (bands from the
|
||
// research entry). Labelling, not simulation.
|
||
var tauMs = tau * 1000;
|
||
var cls = tauMs <= 1 ? "P31" : tauMs <= 150 ? "P1" : "P33";
|
||
var msPerDiv = 1000 / (sweepRate * DIVS_X);
|
||
function set(id, text) {
|
||
document.getElementById(id).textContent = text;
|
||
}
|
||
set("os-r-wave", waveform.toUpperCase());
|
||
set("os-r-freq", frequency.toFixed(frequency < 10 ? 2 : 1) + " Hz");
|
||
set(
|
||
"os-r-time",
|
||
(msPerDiv >= 10 ? msPerDiv.toFixed(0) : msPerDiv.toFixed(2)) + " ms/div",
|
||
);
|
||
set("os-r-amp", amplitude.toFixed(1) + " div pk");
|
||
set("os-r-phos", cls + " tau " + tauMs.toFixed(0) + " ms");
|
||
set(
|
||
"os-r-note",
|
||
"Trace brightness falls as exp(-age/tau) behind the beam, and rises where the beam slows.",
|
||
);
|
||
})();
|
||
|
||
// --- timeline -------------------------------------------------------
|
||
//
|
||
// tl.eventCallback("onUpdate", ...) is NOT usable here: the runtime
|
||
// seeks with suppressEvents, so the callback never fires on a seek and
|
||
// the canvas would keep whatever the last played frame drew. A tweened
|
||
// property with an accessor is applied by GSAP on every render,
|
||
// including suppressed ones, so the repaint is driven from the setter.
|
||
|
||
var beam = { t: 0 };
|
||
var driver = {};
|
||
Object.defineProperty(driver, "t", {
|
||
get: function () {
|
||
return beam.t;
|
||
},
|
||
set: function (value) {
|
||
beam.t = value;
|
||
draw(value);
|
||
},
|
||
});
|
||
|
||
window.__timelines = window.__timelines || {};
|
||
var tl = gsap.timeline({ paused: true });
|
||
tl.to(driver, { t: DURATION, duration: DURATION, ease: "none", lazy: false }, 0);
|
||
window.__timelines[COMP_ID] = tl;
|
||
|
||
draw(0);
|
||
})();
|
||
</script>
|
||
</body>
|
||
</html>
|
||
```
|
||
|
||
</VariablesExplorer>
|
||
|
||
## Install
|
||
|
||
<InstallCommand command="npx hyperframes add oscilloscope-trace" item="oscilloscope-trace" />
|
||
|
||
That writes one file: `compositions/oscilloscope-trace.html`.
|
||
|
||
## Add it to your video
|
||
|
||
It runs for 6 seconds at 1920×1080. Paste this into your composition:
|
||
|
||
```html index.html
|
||
<div
|
||
data-composition-id="oscilloscope-trace"
|
||
data-composition-src="compositions/oscilloscope-trace.html"
|
||
data-start="0"
|
||
data-duration="6"
|
||
data-track-index="1"
|
||
data-width="1920"
|
||
data-height="1080"
|
||
></div>
|
||
```
|
||
|
||
Move it in time with `data-start`. Put it on a different timeline row with
|
||
`data-track-index`. See [data attributes](/concepts/data-attributes) for the rest.
|
||
|
||
## 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 |
|
||
| --- | --- | --- | --- |
|
||
| `waveform` | `sine` | `sine`, `square`, `triangle`, `data` | |
|
||
| `frequency` | `12` | 0.1Hz to 200Hz, step 0.1Hz | |
|
||
| `amplitude` | `3` | 0.1div to 4div, step 0.1div | |
|
||
| `persistenceMs` | `100` | 1ms to 1000ms, step 1ms | |
|
||
| `phosphorColor` | `#5dff8f` | color | |
|
||
| `sweepRate` | `5` | 0.25sweeps/s to 60sweeps/s, step 0.25sweeps/s | |
|
||
| `dataSeries` | `` | string | |
|
||
|
||
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="oscilloscope-trace"
|
||
data-composition-src="compositions/oscilloscope-trace.html"
|
||
data-variable-values='{"waveform":"sine","frequency":12,"amplitude":3,"persistenceMs":100,"phosphorColor":"#5dff8f","sweepRate":5,"dataSeries":""}'
|
||
></div>
|
||
```
|
||
|
||
## Source
|
||
|
||
<Accordion title={`oscilloscope-trace.html`}>
|
||
|
||
```html
|
||
<!doctype html>
|
||
<html
|
||
lang="en"
|
||
data-composition-variables='[
|
||
{"id":"waveform","type":"enum","label":"Waveform","default":"sine","options":[{"value":"sine","label":"Sine"},{"value":"square","label":"Square"},{"value":"triangle","label":"Triangle"},{"value":"data","label":"Data series"}]},
|
||
{"id":"frequency","type":"number","label":"Signal frequency","unit":"Hz","default":12,"min":0.1,"max":200,"step":0.1},
|
||
{"id":"amplitude","type":"number","label":"Amplitude","unit":"div","default":3,"min":0.1,"max":4,"step":0.1},
|
||
{"id":"persistenceMs","type":"number","label":"Phosphor persistence (tau)","unit":"ms","default":100,"min":1,"max":1000,"step":1},
|
||
{"id":"phosphorColor","type":"color","label":"Phosphor colour","default":"#5dff8f"},
|
||
{"id":"sweepRate","type":"number","label":"Sweep rate","unit":"sweeps/s","default":5,"min":0.25,"max":60,"step":0.25},
|
||
{"id":"dataSeries","type":"string","label":"Data series (waveform=data)","default":"","placeholder":"0,0.4,0.9,0.3,-0.6,-1,-0.2,0.5"}
|
||
]'
|
||
>
|
||
<head>
|
||
<meta charset="UTF-8" />
|
||
<meta name="viewport" content="width=1920, height=1080" />
|
||
<title>Oscilloscope Trace</title>
|
||
<script src="https://cdn.jsdelivr.net/npm/gsap@3.14.2/dist/gsap.min.js"></script>
|
||
<style>
|
||
* {
|
||
margin: 0;
|
||
padding: 0;
|
||
box-sizing: border-box;
|
||
}
|
||
html,
|
||
body {
|
||
width: 1920px;
|
||
height: 1080px;
|
||
overflow: hidden;
|
||
background: #05070a;
|
||
}
|
||
#os-root {
|
||
position: relative;
|
||
width: 1920px;
|
||
height: 1080px;
|
||
font-family: "JetBrains Mono", ui-monospace, monospace;
|
||
}
|
||
#os-bg {
|
||
position: absolute;
|
||
inset: 0;
|
||
background: radial-gradient(120% 120% at 30% 25%, #0d141b 0%, #05070a 68%);
|
||
}
|
||
#os-screen {
|
||
position: absolute;
|
||
inset: 0;
|
||
width: 1920px;
|
||
height: 1080px;
|
||
display: block;
|
||
}
|
||
/* Purely decorative CRT falloff — no timing, no motion. */
|
||
#os-vignette {
|
||
position: absolute;
|
||
inset: 0;
|
||
pointer-events: none;
|
||
background: radial-gradient(
|
||
78% 78% at 34% 50%,
|
||
rgba(0, 0, 0, 0) 55%,
|
||
rgba(0, 0, 0, 0.55) 100%
|
||
);
|
||
}
|
||
#os-readout {
|
||
position: absolute;
|
||
left: 1250px;
|
||
top: 150px;
|
||
width: 520px;
|
||
color: #6f8794;
|
||
font-size: 26px;
|
||
line-height: 1.15;
|
||
letter-spacing: 0.04em;
|
||
}
|
||
#os-readout .os-title {
|
||
color: #b9ccd6;
|
||
font-size: 34px;
|
||
letter-spacing: 0.22em;
|
||
padding-bottom: 26px;
|
||
border-bottom: 2px solid #1d2a33;
|
||
margin-bottom: 26px;
|
||
}
|
||
#os-readout .os-row {
|
||
display: flex;
|
||
justify-content: space-between;
|
||
padding: 13px 0;
|
||
}
|
||
#os-readout .os-val {
|
||
color: #d7e6ee;
|
||
}
|
||
#os-readout .os-note {
|
||
margin-top: 28px;
|
||
font-size: 20px;
|
||
color: #6a7b85;
|
||
line-height: 1.5;
|
||
}
|
||
</style>
|
||
</head>
|
||
<body>
|
||
<div
|
||
id="os-root"
|
||
data-composition-id="oscilloscope-trace"
|
||
data-start="0"
|
||
data-duration="6"
|
||
data-width="1920"
|
||
data-height="1080"
|
||
>
|
||
<div id="os-bg"></div>
|
||
<canvas
|
||
id="os-screen"
|
||
class="clip"
|
||
width="1920"
|
||
height="1080"
|
||
data-start="0"
|
||
data-duration="6"
|
||
data-track-index="0"
|
||
></canvas>
|
||
<div id="os-vignette"></div>
|
||
<div id="os-readout" class="clip" data-start="0" data-duration="6" data-track-index="1">
|
||
<div class="os-title">OSCILLOSCOPE</div>
|
||
<div class="os-row"><span>SOURCE</span><span class="os-val" id="os-r-wave">SINE</span></div>
|
||
<div class="os-row"><span>FREQ</span><span class="os-val" id="os-r-freq">-</span></div>
|
||
<div class="os-row"><span>TIMEBASE</span><span class="os-val" id="os-r-time">-</span></div>
|
||
<div class="os-row"><span>VERT</span><span class="os-val" id="os-r-amp">-</span></div>
|
||
<div class="os-row"><span>PHOSPHOR</span><span class="os-val" id="os-r-phos">-</span></div>
|
||
<div class="os-note" id="os-r-note"></div>
|
||
</div>
|
||
</div>
|
||
<script>
|
||
(function () {
|
||
"use strict";
|
||
|
||
// ---------------------------------------------------------------
|
||
// Oscilloscope trace with phosphor persistence.
|
||
//
|
||
// Two pieces of physical truth drive the look:
|
||
//
|
||
// 1. PERSISTENCE. The phosphor keeps emitting after the beam has
|
||
// passed, decaying as exp(-age/tau). Decay constants by EIA
|
||
// phosphor class (research entry F#10):
|
||
// P11/P31 - 0.01-1 ms (what a real bench scope uses: no
|
||
// visible afterglow at video rates)
|
||
// P1 - 80-150 ms (the "vintage glow" look; tau ~= 100 ms
|
||
// is the entry's recommended default)
|
||
// P33 - > 1 s
|
||
// P2/P7 - 30 s .. ~1 min (radar territory, out of range here)
|
||
// The tail window is 3*tau: after three time constants ~5% of the
|
||
// brightness remains, which the entry gives as the safe cutoff.
|
||
//
|
||
// 2. BEAM-VELOCITY BRIGHTNESS. A trace is brighter where the beam
|
||
// moves slower, because the same deposited energy is spread over
|
||
// a shorter path. Each sub-step deposits a fixed amount of energy
|
||
// (constant dt), so surface brightness goes as 1/segment-length.
|
||
// Flat parts of the waveform are bright; fast vertical edges are
|
||
// faint. Qualitative law only - the research entry states it with
|
||
// no proportionality constant, so the reference length below is
|
||
// the physical minimum (pure horizontal sweep motion), not a
|
||
// fudge factor.
|
||
//
|
||
// SWEEP RATE PROVENANCE. The phosphor decay constants above are
|
||
// measured; the sweep rate is NOT - the research entry gives no
|
||
// timebase figure. The default of 5 sweeps/s is authored: across the
|
||
// 10-division graticule it works out to 20 ms/div, a real value from
|
||
// the standard 1-2-5 timebase sequence, picked because it puts a few
|
||
// cycles of the default signal on screen. Treat it as a dial, not as
|
||
// a measurement.
|
||
//
|
||
// NO FEEDBACK BUFFER. The canvas is cleared every frame and the tail
|
||
// is recomputed by evaluating the beam curve backwards in time from
|
||
// the current frame: P(t - k*dt) for k = 0..K. Frame N depends only
|
||
// on N, so seeking anywhere is exact rather than approximate.
|
||
// ---------------------------------------------------------------
|
||
|
||
var COMP_ID = "oscilloscope-trace";
|
||
var DURATION = 6;
|
||
|
||
// Screen geometry: a 10x8 division graticule of SQUARE divisions,
|
||
// the standard CRT scope face.
|
||
var DIV = 100;
|
||
var DIVS_X = 10;
|
||
var DIVS_Y = 8;
|
||
var SW = DIV * DIVS_X;
|
||
var SH = DIV * DIVS_Y;
|
||
var SX = 140;
|
||
var SY = 140;
|
||
var CY = SY + SH / 2;
|
||
|
||
// Tail window in time constants (research entry F#10: 3*tau leaves
|
||
// ~5% weight, stated there as the safe cutoff).
|
||
var TAIL_TAUS = 3;
|
||
// Sub-step count. The entry suggests K ~= 24 steps across the window,
|
||
// which is enough to quantise the DECAY but far too coarse spatially:
|
||
// at 12 Hz the beam would advance 0.15 of a cycle per step and the
|
||
// trace would render as a polygon. So K is derived from how fast the
|
||
// beam actually moves - keep each sub-step under SEG_TARGET_PX of
|
||
// travel. That target and the clamps are MY numbers, not measured
|
||
// ones; the clamp bounds per-frame cost when persistence is long.
|
||
var SEG_TARGET_PX = 3;
|
||
var K_MIN = 120;
|
||
var K_MAX = 8000;
|
||
|
||
// Band-limit for the square wave. A real generator + a real scope
|
||
// front end both have finite bandwidth, so the edge is steep but not
|
||
// instantaneous; a mathematical step would make the vertical edge one
|
||
// sub-step long and the velocity law would erase it entirely.
|
||
var SQUARE_SHARPNESS = 8;
|
||
|
||
function readVariables() {
|
||
var api = window.__hyperframes && window.__hyperframes.getVariables;
|
||
if (typeof api === "function") return api() || {};
|
||
// Standalone fallback (raw file opened without the runtime): read
|
||
// the same declaration the runtime reads, so defaults have exactly
|
||
// one home.
|
||
var out = {};
|
||
try {
|
||
var raw = document.documentElement.getAttribute("data-composition-variables");
|
||
var decls = JSON.parse(raw || "[]");
|
||
for (var i = 0; i < decls.length; i++) out[decls[i].id] = decls[i].default;
|
||
} catch (err) {
|
||
/* declaration missing or malformed - fall through to hard defaults */
|
||
}
|
||
return out;
|
||
}
|
||
|
||
function num(value, fallback, min, max) {
|
||
var n = typeof value === "number" ? value : parseFloat(value);
|
||
if (!isFinite(n)) n = fallback;
|
||
return Math.min(max, Math.max(min, n));
|
||
}
|
||
|
||
var V = readVariables();
|
||
var waveform =
|
||
["sine", "square", "triangle", "data"].indexOf(String(V.waveform)) >= 0
|
||
? String(V.waveform)
|
||
: "sine";
|
||
var frequency = num(V.frequency, 12, 0.1, 200);
|
||
var amplitude = num(V.amplitude, 3, 0.1, 4);
|
||
var tau = num(V.persistenceMs, 100, 1, 1000) / 1000;
|
||
var sweepRate = num(V.sweepRate, 5, 0.25, 60);
|
||
var phosphor = parseColor(V.phosphorColor, [93, 255, 143]);
|
||
|
||
// waveform="data" replays a supplied series instead of a synthetic
|
||
// shape: comma/whitespace separated numbers, clamped to -1..1, linearly
|
||
// interpolated, one full pass of the series per `frequency` cycle.
|
||
// Empty or unparseable -> falls back to sine.
|
||
var series = String(V.dataSeries == null ? "" : V.dataSeries)
|
||
.split(/[\s,]+/)
|
||
.map(parseFloat)
|
||
.filter(function (n) {
|
||
return isFinite(n);
|
||
})
|
||
.map(function (n) {
|
||
return Math.min(1, Math.max(-1, n));
|
||
});
|
||
if (waveform === "data" && series.length < 2) waveform = "sine";
|
||
|
||
function parseColor(value, fallback) {
|
||
var m = /^#?([0-9a-f]{6})$/i.exec(String(value == null ? "" : value).trim());
|
||
if (!m) return fallback;
|
||
var v = parseInt(m[1], 16);
|
||
return [(v >> 16) & 255, (v >> 8) & 255, v & 255];
|
||
}
|
||
|
||
function rgba(c, a) {
|
||
return "rgba(" + c[0] + "," + c[1] + "," + c[2] + "," + a.toFixed(4) + ")";
|
||
}
|
||
|
||
// --- the signal: pure function of time, no state ------------------
|
||
|
||
function wave(t) {
|
||
var p = frequency * t; // cycles elapsed
|
||
if (waveform === "square") {
|
||
return Math.tanh(SQUARE_SHARPNESS * Math.sin(2 * Math.PI * p));
|
||
}
|
||
if (waveform === "triangle") {
|
||
return (2 / Math.PI) * Math.asin(Math.sin(2 * Math.PI * p));
|
||
}
|
||
if (waveform === "data") {
|
||
var frac = p - Math.floor(p);
|
||
var pos = frac * (series.length - 1);
|
||
var i = Math.floor(pos);
|
||
var f = pos - i;
|
||
var a = series[i];
|
||
var b = series[Math.min(series.length - 1, i + 1)];
|
||
return a + (b - a) * f;
|
||
}
|
||
return Math.sin(2 * Math.PI * p);
|
||
}
|
||
|
||
/** Horizontal sweep position, 0..1 across the graticule. */
|
||
function sweepU(t) {
|
||
var s = t * sweepRate;
|
||
return s - Math.floor(s);
|
||
}
|
||
|
||
function beamX(t) {
|
||
return SX + sweepU(t) * SW;
|
||
}
|
||
|
||
function beamY(t) {
|
||
return CY - wave(t) * amplitude * DIV;
|
||
}
|
||
|
||
// Upper bound on beam speed, in px/s, used to pick the sub-step count.
|
||
// Horizontal is the constant sweep; vertical is the waveform's steepest
|
||
// slope, which differs per shape - a band-limited square is
|
||
// SQUARE_SHARPNESS times steeper at its edge than a sine of the same
|
||
// frequency, and under-sampling exactly there is what turns the edge
|
||
// into a polygon.
|
||
var slopeBound;
|
||
if (waveform === "square") {
|
||
slopeBound = SQUARE_SHARPNESS * 2 * Math.PI * frequency;
|
||
} else if (waveform === "triangle") {
|
||
slopeBound = 4 * frequency;
|
||
} else if (waveform === "data") {
|
||
var maxStep = 0;
|
||
for (var si = 1; si < series.length; si++) {
|
||
maxStep = Math.max(maxStep, Math.abs(series[si] - series[si - 1]));
|
||
}
|
||
slopeBound = maxStep * (series.length - 1) * frequency;
|
||
} else {
|
||
slopeBound = 2 * Math.PI * frequency;
|
||
}
|
||
var beamSpeedMax = Math.sqrt(
|
||
Math.pow(SW * sweepRate, 2) + Math.pow(slopeBound * amplitude * DIV, 2),
|
||
);
|
||
|
||
// --- graticule (drawn once to an offscreen canvas) ----------------
|
||
|
||
var grat = document.createElement("canvas");
|
||
grat.width = 1920;
|
||
grat.height = 1080;
|
||
(function drawGraticule() {
|
||
var g = grat.getContext("2d");
|
||
g.fillStyle = "#04080a";
|
||
g.fillRect(SX, SY, SW, SH);
|
||
g.strokeStyle = "rgba(120,180,160,0.16)";
|
||
g.lineWidth = 1;
|
||
for (var i = 1; i < DIVS_X; i++) {
|
||
g.beginPath();
|
||
g.moveTo(SX + i * DIV + 0.5, SY);
|
||
g.lineTo(SX + i * DIV + 0.5, SY + SH);
|
||
g.stroke();
|
||
}
|
||
for (var j = 1; j < DIVS_Y; j++) {
|
||
g.beginPath();
|
||
g.moveTo(SX, SY + j * DIV + 0.5);
|
||
g.lineTo(SX + SW, SY + j * DIV + 0.5);
|
||
g.stroke();
|
||
}
|
||
// Centre axes carry the fine 0.2-division ticks, as on a real face.
|
||
g.strokeStyle = "rgba(150,205,185,0.32)";
|
||
var cx = SX + SW / 2 + 0.5;
|
||
var cy = CY + 0.5;
|
||
g.beginPath();
|
||
g.moveTo(cx, SY);
|
||
g.lineTo(cx, SY + SH);
|
||
g.moveTo(SX, cy);
|
||
g.lineTo(SX + SW, cy);
|
||
g.stroke();
|
||
g.strokeStyle = "rgba(150,205,185,0.42)";
|
||
for (var k = 1; k < DIVS_X * 5; k++) {
|
||
var x = SX + (k * DIV) / 5 + 0.5;
|
||
g.beginPath();
|
||
g.moveTo(x, cy - 9);
|
||
g.lineTo(x, cy + 9);
|
||
g.stroke();
|
||
}
|
||
for (var m = 1; m < DIVS_Y * 5; m++) {
|
||
var y = SY + (m * DIV) / 5 + 0.5;
|
||
g.beginPath();
|
||
g.moveTo(cx - 9, y);
|
||
g.lineTo(cx + 9, y);
|
||
g.stroke();
|
||
}
|
||
g.strokeStyle = "rgba(160,215,195,0.55)";
|
||
g.lineWidth = 2;
|
||
g.strokeRect(SX + 1, SY + 1, SW - 2, SH - 2);
|
||
})();
|
||
|
||
// --- per-frame paint ----------------------------------------------
|
||
|
||
var canvas = document.getElementById("os-screen");
|
||
var ctx = canvas.getContext("2d");
|
||
|
||
function draw(t) {
|
||
ctx.globalCompositeOperation = "source-over";
|
||
ctx.clearRect(0, 0, 1920, 1080);
|
||
ctx.drawImage(grat, 0, 0);
|
||
|
||
var windowS = TAIL_TAUS * tau;
|
||
var K = Math.max(
|
||
K_MIN,
|
||
Math.min(K_MAX, Math.round((windowS * beamSpeedMax) / SEG_TARGET_PX)),
|
||
);
|
||
var dt = windowS / K;
|
||
// Length the beam covers in one sub-step with zero vertical motion.
|
||
// That is the slowest the beam can ever move, so it is the maximum
|
||
// brightness reference and the velocity weight never exceeds 1.
|
||
var lRef = SW * sweepRate * dt;
|
||
|
||
ctx.globalCompositeOperation = "lighter";
|
||
ctx.lineCap = "round";
|
||
|
||
// Oldest -> newest, so the bright head lands on top.
|
||
var prevX = 0;
|
||
var prevY = 0;
|
||
var prevU = 0;
|
||
var havePrev = false;
|
||
for (var k = K; k >= 0; k--) {
|
||
var tk = t - k * dt;
|
||
if (tk < 0) {
|
||
// Before frame 0 the beam had not been switched on yet.
|
||
havePrev = false;
|
||
continue;
|
||
}
|
||
var u = sweepU(tk);
|
||
var x = SX + u * SW;
|
||
var y = beamY(tk);
|
||
if (havePrev && u >= prevU) {
|
||
var dx = x - prevX;
|
||
var dy = y - prevY;
|
||
var len = Math.sqrt(dx * dx + dy * dy);
|
||
// Beam-velocity law: brightness ~ 1 / path length per unit time.
|
||
var vel = len > 1e-6 ? Math.min(1, lRef / len) : 1;
|
||
var decay = Math.exp((-k * dt) / tau);
|
||
var a = decay * vel;
|
||
if (a > 0.002) {
|
||
ctx.beginPath();
|
||
ctx.moveTo(prevX, prevY);
|
||
ctx.lineTo(x, y);
|
||
ctx.strokeStyle = rgba(phosphor, a * 0.13);
|
||
ctx.lineWidth = 13;
|
||
ctx.stroke();
|
||
ctx.strokeStyle = rgba(phosphor, a * 0.9);
|
||
ctx.lineWidth = 3;
|
||
ctx.stroke();
|
||
if (a > 0.55) {
|
||
// Overdriven phosphor saturates towards white at the head.
|
||
ctx.strokeStyle =
|
||
"rgba(255,255,255," + (((a - 0.55) / 0.45) * 0.7).toFixed(4) + ")";
|
||
ctx.lineWidth = 1.4;
|
||
ctx.stroke();
|
||
}
|
||
}
|
||
}
|
||
// Retrace is blanked on a real scope: when u wraps, drop the
|
||
// connecting segment instead of drawing a line back across.
|
||
prevX = x;
|
||
prevY = y;
|
||
prevU = u;
|
||
havePrev = true;
|
||
}
|
||
|
||
// Beam head: the spot itself, brightest point on the screen.
|
||
var hx = beamX(t);
|
||
var hy = beamY(t);
|
||
var glow = ctx.createRadialGradient(hx, hy, 0, hx, hy, 22);
|
||
glow.addColorStop(0, "rgba(255,255,255,0.95)");
|
||
glow.addColorStop(0.22, rgba(phosphor, 0.85));
|
||
glow.addColorStop(1, rgba(phosphor, 0));
|
||
ctx.fillStyle = glow;
|
||
ctx.beginPath();
|
||
ctx.arc(hx, hy, 22, 0, Math.PI * 2);
|
||
ctx.fill();
|
||
|
||
ctx.globalCompositeOperation = "source-over";
|
||
}
|
||
|
||
// --- readout --------------------------------------------------------
|
||
|
||
(function fillReadout() {
|
||
// Nearest EIA phosphor class for the chosen tau (bands from the
|
||
// research entry). Labelling, not simulation.
|
||
var tauMs = tau * 1000;
|
||
var cls = tauMs <= 1 ? "P31" : tauMs <= 150 ? "P1" : "P33";
|
||
var msPerDiv = 1000 / (sweepRate * DIVS_X);
|
||
function set(id, text) {
|
||
document.getElementById(id).textContent = text;
|
||
}
|
||
set("os-r-wave", waveform.toUpperCase());
|
||
set("os-r-freq", frequency.toFixed(frequency < 10 ? 2 : 1) + " Hz");
|
||
set(
|
||
"os-r-time",
|
||
(msPerDiv >= 10 ? msPerDiv.toFixed(0) : msPerDiv.toFixed(2)) + " ms/div",
|
||
);
|
||
set("os-r-amp", amplitude.toFixed(1) + " div pk");
|
||
set("os-r-phos", cls + " tau " + tauMs.toFixed(0) + " ms");
|
||
set(
|
||
"os-r-note",
|
||
"Trace brightness falls as exp(-age/tau) behind the beam, and rises where the beam slows.",
|
||
);
|
||
})();
|
||
|
||
// --- timeline -------------------------------------------------------
|
||
//
|
||
// tl.eventCallback("onUpdate", ...) is NOT usable here: the runtime
|
||
// seeks with suppressEvents, so the callback never fires on a seek and
|
||
// the canvas would keep whatever the last played frame drew. A tweened
|
||
// property with an accessor is applied by GSAP on every render,
|
||
// including suppressed ones, so the repaint is driven from the setter.
|
||
|
||
var beam = { t: 0 };
|
||
var driver = {};
|
||
Object.defineProperty(driver, "t", {
|
||
get: function () {
|
||
return beam.t;
|
||
},
|
||
set: function (value) {
|
||
beam.t = value;
|
||
draw(value);
|
||
},
|
||
});
|
||
|
||
window.__timelines = window.__timelines || {};
|
||
var tl = gsap.timeline({ paused: true });
|
||
tl.to(driver, { t: DURATION, duration: DURATION, ease: "none", lazy: false }, 0);
|
||
window.__timelines[COMP_ID] = tl;
|
||
|
||
draw(0);
|
||
})();
|
||
</script>
|
||
</body>
|
||
</html>
|
||
```
|
||
|
||
</Accordion>
|
||
|
||
{/* hf:generated-footer */}
|
||
|
||
Tagged `instrument` `data` `showcase` `retro`.
|
||
|
||
## Related topics
|
||
|
||
- [Browse the complete Catalog](/catalog)
|
||
- [Add assets and Catalog items in Studio](/studio/assets-and-blocks)
|
||
- [Build a richer composition](/go-further)
|