spike(hdr): extended-range HDR canvas output behind ?hdr#497
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The renderer already works in HDR internally (rgba16float offscreen) and
tone-maps to an 8-bit swap chain in one final compositor pass. This spike
lets that signal reach an HDR display:
- device.ts: when ?hdr is set AND the display reports (dynamic-range: high),
the swap chain becomes rgba16float + toneMapping { mode: 'extended' }.
Off by default; SDR path byte-identical. Threads `hdr` through GpuContext
→ EngineGpuHandles → ReadyFrameContext.
- compositor: two free uniform lanes (bytes 24/28) carry hdrKneeStart +
hdrHeadroom; the tone pass spills over-white energy above the knee back
on top of the clamped curve so bright sources punch into headroom. With
headroom 0 (SDR) the output is unchanged.
- renderFrame: sets headroom/knee from ctx.hdr; constants tunable.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Captures what the ?hdr spike investigation surfaced: six incompatible per-layer brightness "currencies" (galaxies/stars/planets/Sun/Milky Way) under one static exposure, and how Gaia Sky / SpaceEngine / Stellarium solve multi-scale viewing with scene-adaptive auto-exposure on a shared magnitude scale. Adds the docs/backlog detail file + a terse BACKLOG index line under Rendering. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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| Status | Name | Latest Commit | Preview URL | Updated (UTC) |
|---|---|---|---|---|
| ✅ Deployment successful! View logs |
skymap | a6146c6 | Commit Preview URL Branch Preview URL |
Jul 23 2026, 10:14 AM |
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What
Exploratory spike proving skymap can drive an HDR display. The renderer already works in HDR internally (every pass draws into an
rgba16floatoffscreen); a single final compositor pass tone-maps down to an 8-bit swap chain and clamps to[0,1]. This spike lets that signal reach the display.Gated behind
?hdr+ a(dynamic-range: high)display check — off by default, and the SDR path is bit-identical when the flag is off.device.ts: when engaged, the swap chain becomesrgba16float+toneMapping: { mode: 'extended' }(Chrome HDR-canvas API).formatis the single source of truth threaded to every swap-target renderer, so it propagates with no other wiring.hdris threadedGpuContext → EngineGpuHandles → ReadyFrameContext.hdrKneeStart+hdrHeadroom; the tone pass spills over-white energy above the knee on top of the clamped curve, so bright sources (Sun, bloom, bright stars) punch into headroom.hdrHeadroom = 0(SDR) adds nothing.renderFrame.ts: sets headroom/knee fromctx.hdr;HDR_KNEE_START/HDR_HEADROOMare tunable constants.How to test
Open with
?hdron an HDR display (Chrome, OS HDR on). Bright sources should punch past paper-white; mid-range looks identical to SDR. Without?hdror on an SDR display it silently falls back — no visible change, no wasted allocation.Tuning knobs (HMR-hot,
src/services/engine/frame/renderFrame.ts):HDR_HEADROOM(default 0.25) andHDR_KNEE_START(default 1.0).Status
Spike, visually confirmed on an HDR display — looks good. Verified: typecheck clean (both tsconfigs), full suite green (4982 tests), SDR path bit-identical.
The investigation this spike seeded — how brightness should be rebalanced across all six layers, and how other explorers (Gaia Sky / SpaceEngine / Stellarium) handle multi-scale viewing with auto-exposure — is written up in
docs/backlog/2026-07-23-hdr-brightness-rebalance.mdwith aneeds-designbacklog entry. That larger design is deliberately out of scope here.🤖 Generated with Claude Code