# Lighting

## Principle

Lighting is a Component system and a composition system. It establishes atmosphere, depth, focus, state and material belonging.

The supported source vocabulary includes sunlight, moonlight, skylight, fire, lanterns, candles, luminous Portals, bioluminescence, fireflies, intelligent or generated illumination and reflected environmental light. Each resolves through the same receiving model rather than carrying a separate visual effect language.

## Universal authoring rig

Transparent Components are authored under a neutral rig:

- warm upper-left key, azimuth 315°, elevation 42°;
- cool upper-right fill at 8–14% of key strength;
- ambient color inherited from the preview fixture, never neutral gray;
- soft separable contact shadow;
- no horizon, room color or strong local Scene atmosphere baked into the asset.

## Five-part receiving model

1. **Ambient** establishes the Scene’s base color and minimum visibility.
2. **Directional** establishes shared form, cast-shadow direction and environmental time.
3. **Local** comes from fire, lanterns, portals, bioluminescence and intelligent light.
4. **Rim** separates silhouettes from dark architecture without outlining them.
5. **Reflection** carries nearby warm/cool color into brass, glass, water, cream textile and polished stone.

## Emission

Every emitter declares color role, intensity 0–1, range in WU, falloff and an emitter anchor. Emission masks are isolated from baked color so Scene intensity can change. A light-emitting Component still receives ambient, rim and reflected light.

## Shadow

- Contact shadow anchors the object to its receiving plane.
- Cast shadow follows the Scene directional light unless explicitly local.
- Shadow hue is a darkened complement of the environment, never pure black.
- Penumbra grows with distance from the caster.
- Foreground shadows may cross technical tile boundaries.

## Atmospheric perspective

With increasing camera distance: contrast falls; saturation narrows; edge hardness softens; texture frequency decreases; temperature approaches sky/haze; and small cast shadows merge into value masses.

## State through light

- available: near-field warmth rises 6–10%;
- focused: light gathers at the interaction anchor;
- selected: material and local reflection brighten, not the silhouette alone;
- active: emitter and nearby reflection participate together;
- locked/unavailable: light withdraws while the object remains materially complete;
- urgent: a slow warm/cool tension replaces flashing red.

## Reduced motion and photosensitivity

No light state may flash faster than 3 Hz. Reduced-motion mode replaces pulsing with a stable value change and a non-color cue. Portal activation uses a single 240–420 ms luminance resolve rather than repeated strobing.