# Threejs Exposure Color Grading

> Build a measured exposure and grading path in Three.js. Use for a 64x36 encoded luminance meter, asynchronous readback, weighted log-average exposure, asymmetric adaptation, single tone-map ownership, and a generated 32-cube post-tone-map LUT.

- Skill: `gabrielmoreira/threejs-exposure-color-grading` (Agent Skill, multi-file: 3 files)
- Install (CLI): `npx skillmds@latest add gabrielmoreira/threejs-exposure-color-grading`
- Raw SKILL.md: https://api.skillmd.com/api/skills/gabrielmoreira/threejs-exposure-color-grading/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- Author: gabrielmoreira (https://skillmd.com/u/gabrielmoreira)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/gabrielmoreira/threejs-exposure-color-grading

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# Exposure and Color Grading

Treat exposure, tone mapping, grading, and output conversion as distinct stages. Tune them from measured HDR signal, not by stacking compensating color operations.

## Order

```text
HDR scene
  → luminance meter
  → adapted exposure
  → tone map
  → creative grade / 3D LUT
  → final output conversion
```

Read [references/scene-referred-color-pipeline.md](references/scene-referred-color-pipeline.md)
for the exact 64x36 meter, encoded readback, adaptation constants, 32-cube LUT,
and signal-ownership ambiguities.

## Failure conditions

- tone mapping occurs in both materials and post;
- exposure is used to repair physically inconsistent light ratios;
- meter weighting and scene framing are not inspected;
- adaptation speed is the same toward light and dark;
- LUT input/output spaces are undocumented;
- sRGB encoding happens twice;
- a display-domain LUT is moved before tone mapping without being rebuilt.

## Routing boundary

Use `$threejs-bloom` for HDR glow contribution and
`$threejs-image-pipeline` when this color path must share ownership with AO,
atmosphere, or effect-local render targets.