Optional eye adaptation

autoExposure.ts reduces the existing unexposed colour texture in 4×4 blocks and adapts in log2 space on separate 1×1 ping-pong targets. Odd-sized edge blocks are masked rather than repeated. There is no extra scene draw, tonemapper, or render loop. Wire it ahead of bloom and the output transform; never multiply both its absolute exposure and the old constant. applyExposure scales RGB and preserves alpha: multiplying a whole vec4 darkens low-exposure output again when the browser composites its reduced alpha onto the page.

For an existing WorldEnvironment chain, its baseColour callback already supplies the world pass:

const world = new WorldEnvironment({
  ...qualityPreset("high"),
  autoExposureEnabled: true,
  exposurePolicy: { ...exposureSettings, enabled: true },
});
const applied = world.apply(renderer, scene, camera);
const eye = applied.exposure;
// The installed graph owns the meter and its existing world pass.
applied.dispose?.();

Import the classes/functions from this game's src/render/ files. If a baseColour composition already exists (for example aerial perspective), meter that scene-referred composition using its existing texture; do not create a second scene pass. Keep the existing chain's output cleanup.

• eye.setEnabled(false) keeps measuring and tracking the hypothetical adaptation while returning exactly the supplied constant. The graph must remain attached, so application opt-out never silences measurement. The separate autoExposureEnabled: false cost flag omits the graph entirely. quality.ts decides when to apply the convention; this file decides its look.
• eye.reset() adopts the next measured target; eye.reset(value) seeds a known cut. Reset only for an authored cut/level load. Resizing changes meter targets but preserves the 1×1 history.
• eye.getObservation() and TN_AUTO_EXPOSURE report actual GPU luminance, applied stops, target stops, settled state and applied. Before the first readback, or on invalid readback, measured is false; it never fabricates a zero reading. Diagnostic readbacks are bounded to one in flight.
• A replaced chain owns a replaced node. Dispose the old pair; do not leave a second history graph alive. Continuous quality-rebuild history transfer is not yet integrated with setupPost.

Qualify an authored policy using the same camera in dark and bright poses, cuts in both directions, known resets, viewport/resolution changes and disabled measurement. Inspect actual canvas captures and the named adapter. A software-adapter image proves pixels, not native support or hardware cost.