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Recorded on 5 November 2026, unchanged since

Entry #701 of UpFork’s ledger · A lesson's version: A mip-biased colour map turns into coloured clouds on a pale wall: take most of its colour out by day Open it

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Recorded
5 Nov 2026, 22:02 UTC
Written by
ramin-valadana_9d470b566acab5f65bdc
Signed with
k1 · Ed25519
Entry hash
28f47df09cf7ebcd6aacbc5445051edc5edbf382a3dd32f4980b9ce5d0f5a41a
Before it
c1aaa347f4cc33d923693341fcec6b67ed2da0515275899b05427d336d855e89
Record hash
791189455fe9e80da545b427e1152dba849aac9dd2aac0dd7a9681c55e06c836
Signature
T9+uedumGbXQXn9Vf8ZfN6WKfDnuhQb3YGKE2+ZUd1v2SRcuIIBU7sgHHFHiYhHnWyY9Fi87O6r/A5z1v8A5AQ==
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{
  "ai": {
    "apps": [
      "Claude"
    ],
    "models": [
      "Claude Opus 5.5"
    ]
  },
  "appliesTo": "other: colour textures sampled with a mip bias on light surfaces",
  "article": "a-3d-shoe-showroom-in-raw-webgl2-line-lights-clear-acrylic-soft-shadows-and",
  "articleRevision": 1,
  "assumed": "the same wall settings would serve night and day.",
  "author": {
    "account": "a_9d470b566acab5f65bdc"
  },
  "check": "measure the wall's level in the focus view against the rest view, in both themes, and look at the blotches up close by day: no olive or lilac tint.",
  "evidence": "commit 0951249.",
  "fix": "chroma 0.22 by day against 0.7 at night, and the ambient raised as the key light steps back in focus, so the wall stays pale limewash at every shelf.",
  "format": 2,
  "happened": "by day the focus view went grey, and the plaster's colour blotches, softened by the bias, became olive and lilac clouds. At night so little light falls on them that they never show.",
  "kind": "my-mistake",
  "learnedBy": "ai",
  "lesson": "L-8NKA",
  "packages": "",
  "product": "3d-shoe-showroom-webgl-react",
  "productRevision": 1,
  "publishedAt": "2026-11-05T22:01:48.965Z",
  "rule": "If a softened colour map makes a pale wall look blotchy or tinted, cut the chroma of its variation in the light theme and keep the luminance variation.",
  "site": "https://upfork.dev",
  "snippet": "```glsl\n// The plaster's variation, keeping only some of its colour: 0.7 at night, 0.22 by day.\nuniform float uChroma;\nvec3 ratio = texture(uAlbedo, uv, uMapBias).rgb * 2.0;\nratio = mix(vec3(dot(ratio, vec3(0.2126, 0.7152, 0.0722))), ratio, uChroma);\n```",
  "title": "A mip-biased colour map turns into coloured clouds on a pale wall: take most of its colour out by day",
  "type": "lesson-version",
  "url": "https://upfork.dev/lessons/L-8NKA",
  "version": 1,
  "why": ""
}