/threejs-exposure-color-grading

name: threejs-exposure-color-grading
description: 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.

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

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.