Bloom

Bloom is a camera/display response to bright HDR signal. Establish scene exposure and emissive luminance before tuning blur.

Workflow

1. Inspect pre-tone-map luminance.
2. Choose which scene values should bloom.
3. Choose a single-node or dual selective-render ownership model.
4. Calibrate threshold, radius, smooth width, and strength in HDR.
5. Restore all substituted materials transactionally for selective passes.
6. Composite before exposure/tone mapping.
7. Validate base, contribution, and final views.

Read references/hdr-bloom-system.md for the HDR ordering, dual selective-bloom transaction, compact emissive hierarchy, and the costs and limits of each ownership model.

Apply the material substitution/restoration ownership pattern in the reference before adding selective bloom to a composed scene.

Failure conditions

• bloom creates the only visible form of an effect;
• all bright materials share one arbitrary emission multiplier;
• threshold is tuned after tone mapping;
• selective bloom requires mutating scene materials every frame without restoration guarantees;
• transparent particles disappear from extraction because pass ownership is unclear;
• bloom radius changes wildly with resolution;
• highlights become gray because energy is clamped too early.

Routing boundary

Use $threejs-exposure-color-grading for metering, adaptation, tone mapping, and LUTs. Load $threejs-image-pipeline only when bloom must be composed with several shared image-space systems. A per-pixel ray integrator that owns its own reduced-resolution target and accumulation history keeps its bloom internal; route that to $threejs-raymarched-space-effects.