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 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.