58 lines
4.9 KiB
Markdown
58 lines
4.9 KiB
Markdown
# Flash analysis evidence
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Status date: 2026-09-02
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## Shipped surfaces in scope
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- Procedural journey scene in its default and scroll-accelerated states.
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- Static and `prefers-reduced-motion` poster states.
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- Project media: **not applicable yet**. The public asset manifest is intentionally empty while final derivatives and imagery rights await Luca's approval. This record must be extended before any video or animated project asset is published.
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## Automated method
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`tests/browser/visual-regression.spec.ts` captures the real `.journey-world` at 10 frames per second. The accelerated sequence receives two production wheel inputs before a two-second capture. Static and reduced-motion sequences are captured separately.
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Each frame is downsampled to 160×90 RGB pixels. Between adjacent frames, a pixel is classed as a general-flash luminance change when:
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1. relative luminance changes by at least 0.1; and
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2. the darker state is below 0.8.
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A transition is conservatively treated as large-area when one direction affects at least 25% of the sampled viewport. Within every rolling one-second window, opposing large-area transitions are paired into flashes. The test fails above three flashes per second. JSON event evidence is attached to the Playwright result for the live, Static, and reduced-motion sequences.
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This deliberately conservative area rule does not use the WCAG small-area exemption. It checks luminance flash, not red-flash chromaticity in isolation; the shipped scene contains no full-field saturated-red strobe, and the manual review below remains required.
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## Automated result
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| Engine/state | Result | Evidence |
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| -------------------------------------------------------- | -------------------------------------------------------------- | ---------------------------------------------------------- |
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| Chrome for Testing 151.0.7922.34, accelerated live scene | **PASS — no rolling one-second window exceeded three flashes** | `live-scene-flash-analysis.json` Playwright attachment |
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| Chrome for Testing 151.0.7922.34, Static | **PASS — zero qualifying flashes** | `static-flash-analysis.json` Playwright attachment |
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| Chrome for Testing 151.0.7922.34, reduced motion | **PASS — zero qualifying flashes** | `reduced-motion-flash-analysis.json` Playwright attachment |
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These results came from Playwright 1.62.1 and were reconfirmed in the final successful complete browser run (157 passed, 41 deliberate skips):
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```text
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npm run test:browser -- tests/browser/visual-regression.spec.ts
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```
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## Required human/platform evidence — pending, not passed
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- [ ] Review the accelerated scene at normal speed and during repeated direction changes; record reviewer, date, display refresh rate, and result.
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- [ ] Review every final encoded project video/animation after its exact approved bytes are bound into the public manifest.
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- [ ] Run the automated capture in current Firefox and WebKit/Safari-capable infrastructure and attach the corresponding JSON.
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- [ ] Run the automated capture in current Edge and the previous stable desktop majors named by the release matrix.
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- [ ] Review on the physical iPhone 13 and Pixel 6 during `physical-drive.v1`.
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No unsupported engine, physical device, or unpublished project-media result is represented as passed.
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## Underpass shade (chapter boundaries)
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Every chapter boundary is an overpass deck the car drives beneath (`src/scene/world/underpass.ts`, pure rules in `src/journey/underpass.ts`). While the deck is overhead it dims the sky, the fog and the sky-lit road and terrain terms. By construction:
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- **One dark-light cycle per boundary.** The shade follows the deck's distance from the camera: it rises once as the deck arrives and falls once as it leaves. Scrolling back reverses the same single cycle.
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- **Maximum dip 35%.** The shade multiplier never goes below 0.65 (`SHADE_PEAK = 0.35`). The headlight throw, lamps and HUD are not dimmed.
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- **Edges of at least 300 ms.** The shade is slew-limited: 0 to the 35% peak, or back, takes at least 300 ms (`SHADE_EDGE_SECONDS`), however fast the scroll.
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- **A latch of at least 1 s.** Whether a pass shades at all is decided once, as the deck enters the band, and a pass starting within 1 s of the last shaded pass gets no shade (`SHADE_SPACING_MS`). Brisk scrolling (drive speed above 0.5, the exit sign's own gate) and explicit navigation never shade: the deck goes by without dimming or sound.
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The worst case is therefore one shade cycle per second, at most **1 Hz**, well under the three-per-second limit, and each cycle is a 35% dip with soft edges, below the general-flash luminance pair the automated method counts at large area. The low tier draws the deck without any shade. Static, reduced-motion and data-saver visits get no scene, so nothing is added there.
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