The remaining lighting tiers from the original proposal, all extending the
deterministic accumulation core (light.ludic) — no new ECS plumbing:
- Light.spot: cone / flashlight lights (direction + spread degrees), with a
self-contained integer atan2-in-degrees and a feathered edge.
- Light.falloff: a brightness-ramp exponent (1 linear, 2 quadratic, …) via
repeated fixed multiply.
- Light.soft: soft shadows — an area-sampled light so an occluder edge fades
through a penumbra instead of a hard cut.
- Light.gel + Light.clear_gel: colour cookies — a light gels from its centre
colour to a rim colour.
- Light.normal + Light.clear_normals + Light.height: a normal G-buffer so
surfaces shade by facing (N·L), not distance alone (tier 3).
- Light.time_of_day: a day/night ambient ramp from a single 0..1 value.
The engine lighting system (systems_light.ludic) consumes matching optional
Light2D fields — direction/spread/falloff/softness/gel — each defaulting off so
an older five-field Light2D lights exactly as before. Every tier is integer +
Q16.16 fixed, so scenes light identically on every run and headless.
Worked example + regression: examples/library/light_tiers.ludic (1 1 1 1 1 1 1 1 1).
Nine new docs/language/light pages. Full suite 76 passed, self-host C-free
fixpoint intact, no golden drift.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
A software light pass over the framebuffer, run in a render phase after drawing
the scene: Light.ambient multiplies the scene toward a tint (night/cave mood),
Light.point additively accumulates a radial glow with linear falloff clamped per
channel, and Light.occlude / Light.clear_occluders cast hard shadows by blocking
a light's rays against rectangular occluders. Integer + Q16.16 fixed throughout,
so a scene lights identically every run and in a headless render (diffable).
Engine in runtime/native/light.ludic, spliced on demand (g_uses_light) like the
regex/query runtimes; namespace wired in emit_call.ludic. Ships issue #4 tiers 1
(ambient + additive radial lights) and 2 (hard shadows). Normal-mapped sprites,
soft shadows, a day/night directional light, and auto-consuming Light2D/Occluder
components are follow-ups (the auto-system hook is tracked by #43).
- runtime/native/light.ludic: the light-accumulation engine (isqrt falloff,
segment/occluder shadow test, ambient modulate)
- examples/library/lighting.ludic: 14 pixel-readback assertions
- docs/language/light/: Light.ambient/point/occlude/clear_occluders
- tools/x/test.ludic: lighting.ludic in the regression suite
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
