ludic/docs/language/light/light-occlude.md
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feat(rendering): add Light.* — deterministic 2D light accumulation with hard shadows (#4)
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>
2026-08-31 14:07:19 +03:00

1.2 KiB

id name category kind tokens sig tip order ns member
light-occlude Light.occlude light namespace-method Light.occlude Light.occlude(x, y, width, height) Register a rectangle that blocks light — a hard shadow caster. 3 Light occlude

Registers an axis-aligned rectangle (screen space) that blocks light: for every Light.point that follows, any pixel whose ray from the light centre crosses this rectangle — or lies inside it — is left in shadow, carving a hard umbra behind the wall. Register the geometry that should cast shadows this frame, then draw the lights. Occluders persist until Light.clear_occluders, so call that once per frame first; up to 64 occluders are kept.

Parameters:

  • x, y — the top-left corner, in screen pixels
  • width, height — the rectangle size in pixels
program Demo {
  property Wall { x: int = 0, y: int = 0 }
  model Block { Wall }
  handler Render phase Update {
    Screen.clear(0)
    Light.clear_occluders()
    Light.occlude(120, 80, 8, 48)                 # a pillar
    Light.point(60, 100, 120, Color.rgb(255, 240, 200), 1.0)
    Screen.show()
  }
}