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Earth's night side is lit about 30% on the bare ellipsoid when ion's World Terrain is unavailable

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  • ¿Algo no está bien?
#210 0 comentarios 0 reacciones 0 asignados Ver en GitHub

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Evaluación

Dificultad
4/5
Tiempo estimado
3-5 días
Aptitud para principiantes
48/100
Tipo de issue
Error
Claridad
Bien especificado
Estado de actividad
Activo
Stack tecnológico
javascript
Área
computer-graphics

Línea de trabajo

Start with the linked CESIUM.md section and review #202 for context on the two shading paths: terrain vertex lighting and ellipsoid day/night shading. Compare the decode-pass option with a flat terrain provider that supplies normals, then run the earth-night-* parity views with the ion token unset. Done means the ellipsoid night side is as dark as with terrain, and city lights have the same exposure.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

cesium track:rendering

Found in review of #202; written up in CESIUM.md, Earth's lighting needs the terrain, and listed there as not fixed.

Problem

Cesium lights a globe two ways. With terrain that has vertex normals (ion's World Terrain, requested with requestVertexNormals) it uses ENABLE_VERTEX_LIGHTING, which litSurfaceOnly sets to Lambert × 1 + 0: dark on the night side, as celestiary's own Earth. On the plain ellipsoid it uses ENABLE_DAYNIGHT_SHADING, colour × clamp(5 × Lambert + 0.3), hard-coded. The 0.3 is a floor all over the night side, and as the exposure meter takes the night side's brightness for the scene's, it also dims the exposure the city lights are seen at.

So whenever the globe is on the ellipsoid, Earth's night side shows the day surface at about 30% and the lights are dimmed: until the terrain answers, and for good when ion refuses it (no token, a token not scoped to asset 1, a 401 or 403 from the account's quota, or a build with CESIUM_ION_TOKEN= as AGENTS.md now suggests for testing). Production with a working token is unaffected; PR previews, local builds without the token and an over-quota account are not.

Options (from CESIUM.md)

  • Apply the ellipsoid's shading in the decode pass, taking the 0.3 floor out (the decode already inverts Cesium's frame).
  • A flat terrain provider that supplies normals, so the globe takes the vertex-lighting path without ion.

Done when

With ion's terrain refused, Earth from 30,000 km shows the night side as dark as with terrain on (the parity earth-night-* views pass with the token unset), and the city lights are at the same exposure.

Related: #202, #93, #110.

Lenguaje dominante
JavaScript
Estrellas
55
Forks
4
Merge medio
10 h 12 min
PR fusionados (30 d)
134

Preparar el entorno

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Primeros pasos

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  3. Haz un fork del repositorio y trabaja en una rama.
  4. Abre un pull request que haga referencia al número del issue.

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