Lighting

This group covers the light kinds, curated rigs, and cast shadows.

Sketch	What it shows
Lighting	The three light kinds placed by hand to shade solids: a fixed directional key, an orbiting point bulb, and a sweeping spot. A row of spheres shows rising `specularSharpness`.
LightSets	One frame, several lighting rigs. Three rooms side by side, each lit by `withLights` from its own fixture: a swinging warm bulb, a cold overhead strip, a green glow out of the floor. Every back wall carries the same plate drawn `withoutLights`, so the three walls come out warm, cold and green while the three plates come out identical.
LightingPresets	One call relights the whole scene. The curated `LightingPreset`s (`.standard`/`.threePoint`/`.goldenHour`/`.noir`/`.studio`/`.moonlight`) cycle over one still life, plus a custom rig built in the sketch. Click or press a key to step.
Shadows	Directional cast shadows. Solids drop shadows onto a floor and onto one another through `castShadows()`.
SpotShadow	A spot light as the shadow caster. A perspective shadow map is fit to its cone, so the solids inside the beam drop crisp shadows.
PointShadow	A point light as an omnidirectional caster. A bulb at the center throws shadows in every direction, ray-traced on an RT GPU and through a depth cube elsewhere.
ManyCasters	Several casters at once. A warm key is joined by a swinging spot or by two circling point lamps, and each throws its own shadow.
AreaLights	Rect, disk, and tube sources shading a small studio set. The softbox grows and shrinks, and the softness of its shadows follows its size.
LightShaping	Photometric profiles and a projected cookie, the two ways a real fixture shapes its beam.
ManyLights	A courtyard at night with sixty-four drifting lamps in it. Each one is given a `reach`, so it lights its own corner and nothing past it, and the renderer shades a pixel against the lamps standing over it.
VolumetricLight	Beams, gobos, and shafts you can see in the air.
Caustics	The light a glass or a polished metal focuses onto what is around it.
GlobalIllumination	Light that bounces, so a red wall reddens what stands beside it.

Run one with swift run Example-3D-Lighting-<Name>, for example swift run Example-3D-Lighting-Lighting.