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2026 ED138 from the Rubin seat at a 0.00016° field: the disc blinks, the ring jumps, the path and the orbit line miss (float32 at 47 au)

Aperta
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#334 1 commento 0 reazioni 0 assegnatari Vedi su GitHub

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Valutazione

Difficoltà
5/5
Tempo stimato
Più di una settimana
Idoneità per principianti
35/100
Tipo di issue
Bug
Chiarezza
Specificata chiaramente
Stato di attività
Attiva
Stack tecnologico
javascript, three.js
Ambito
computer-graphics

Direzione di ricerca

Read js/scene/rubin/Rubin.md, HDR.md and DESIGN.md for the seat, far point and LOD hand-off; reproduce the reported view near 47 au at a 0.00016° field. Compare the mesh, path and orbit line precision and depth behavior across the proposed approaches. Done means choosing and implementing a fix that keeps the disc, path and orbit line stable and correctly occluded at close zoom.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

From the Rubin seat (#327, #328), zoomed with the field-of-view keys to about 0.00016° (0.6″ across the frame), on the maintainer's GPU (the preview of #320, 2026-10-28). Not reproduced headless on SwiftShader at pixel ratio 1 or 2: there the planet LOD is at level 0 (the mesh), the far point hidden, and the disc draws whole.

What it looks like (the maintainer's captures)

The clock paused at 256×, the night of 15 May 2026, a few steps of time apart:

  1. Gone: the disc not drawn at all; the path's ring well off the orbit line.
    'https://celestiary.org/web/pr-preview/pr-320/#sun/[email protected],-70.7494,1.689km;from=sun/earth;t=9630.794665jd;cq=0.7206,0.557,0.0889,-0.4032;fov=0.0001615deg;s=LTF;time:pause,rate=-256;apps:open,view=rubin'
Image
  1. A crescent: part of the disc, the dark bite with a curved edge.
    'https://celestiary.org/web/pr-preview/pr-320/#sun/[email protected],-70.7494,1.689km;from=sun/earth;t=9630.806745jd;cq=0.7312,0.5532,0.1064,-0.3846;fov=0.0001615deg;s=LTF;time:pause,rate=256;apps:open,view=rubin'
Image
  1. Whole: the disc drawn, the blue orbit line across its face, not occluded by it.
    'https://celestiary.org/web/pr-preview/pr-320/#sun/[email protected],-70.7494,1.689km;from=sun/earth;t=9630.807563jd;cq=0.7319,0.5529,0.1076,-0.3834;fov=0.0001615deg;s=LTF;time:pause,rate=256;apps:open,view=rubin'
Image Image

Also at that field: the green apparent path doesn't meet the blue orbit line; the path's ring (the body's place at the clock's time) jumps about between frames while everything else moves smoothly. Zoomed out to 1° the same view is fine.

Image

Where it lives

A 500 km body at 47 au is one part in 1.4e7 of its distance, past float32's 2^23. Everything at 7e12 m from the camera is held to float32's spacing there, 5e5 m, which is 7e-8 rad, 0.015″: at a 0.00016° field that is 50 to 200 px.

  • The mesh: its vertices land to within half the body's radius, differently per GPU and per frame as the camera moves (time running), so the disc jumps, loses parts, or isn't drawn (1, 2).
  • The path and the ring: the path's points are a Float32Array of positions at the body's distance (since #320 put the path at its true distance), quantised to 5e5 m, and the ring interpolates between two of them: the jump between frames is the quantisation stepping as the clock moves. The orbit line's vertices are float32 in the Sun's frame, quantised the same way but not on the same steps, so the two lines miss each other by up to a step.
  • Depth: the body's depth from the seat, 1 − 169 m / 7e12 m, is 1.0 in a 24-bit buffer, the same as empty sky, so nothing occludes against it: the orbit line draws across the disc (3), and the passes that read depth (the atmosphere's night sky, the galaxy's pin) can't tell the body from the sky either.

Pluto at 39 au and 1,200 km is just inside the limit; no other body reaches it.

That field is 20× past Rubin's own pixels

Rubin's pixels are 0.2″; the view at 0.6″ across the frame resolves nothing real, and the body's 0.03″ disc is a point to any telescope on Earth. Options:

  • a field-of-view floor from the seat (or landed) at the instrument's resolution, a few arcseconds, where none of this shows (the maintainer's 1° frame is right);
  • or keep the far point for a body whose distance over its radius passes 2^22, and draw no mesh there (the lines and the ring still quantise);
  • or relative-to-eye placement of far things: the body's centre, the path's and the orbit line's points held in float64 on the CPU and uploaded as offsets from the camera each frame, which is the general fix and the costliest.

Design notes: js/scene/rubin/Rubin.md (the path, the seat), HDR.md (the far point), DESIGN.md (the far point and the LOD hand-off).

Lingua principale
JavaScript
Stelle
55
Fork
4
Merge medio
10h 12m
PR unite (30g)
134

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Come iniziare

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