[stellarfeline]

A stated sky can stand at a tick and ask for the game's look

A caller that states its sky (Sky::Stated) used to get Chunky's look every time. 0.2.0's StatedSky had no field for a tick or a look. The HQ day weight was fixed at 1, the environment was sampled at the world's DayTime, and the stated quick sky drew no sunrise glow, moon or stars. A frame that states its sky at dusk therefore came out with Chunky's yellow cast where the game shows orange.

API

• StatedSky::tick: Option<StatedTick>. StatedTick { time, look, render_distance } is built by StatedTick::new(time, look); StatedSky::at(tick) sets it.
• StatedSky::new(quick, hq) is a stated sky at no tick, and draws what 0.2.0 drew.
• QuickSkyColours::vanilla(env, biome, time, sun_dir, forward, draw_distance) returns the colours Sky::Vanilla derives, so a caller can state Lumenwright's own reading.
• StatedSky and StatedTick are #[non_exhaustive].

Semver: this breaks 0.2.x. Adding a field to an exhaustive public struct breaks every struct literal, and that is true whether the new field has a default or comes with a constructor. Neither option keeps semver. The constructors together with #[non_exhaustive] make this the last such break: a later field is additive. Under Cargo's rule for 0.x, the next release containing this is 0.3.0. Callers move from StatedSky { quick, hq } to StatedSky::new(quick, hq).

Behaviour at a stated tick

• The environment is sampled at tick.time.
• The HQ weight comes from the stated look through look_weight, the one function Sky::Vanilla also uses. ByTime calls sky::day_weight, Game is 0, Chunky is 1. StatedSky::hq is Chunky's part of the frame.
• Both modes draw the tick's sunrise glow, moon and stars through tick_celestials, the one function the vanilla arm also draws them with. Under Sky::Vanilla, quick_sky now gets its colours from QuickSkyColours::vanilla, so the stated and vanilla arms differ only in where the colours come from.

Tests

• a_stated_sky_at_a_tick_is_the_vanilla_sky_at_it (lumenwright-cli/tests/library.rs) states QuickSkyColours::vanilla and sky::hq_sky at the same sun. Each frame must equal Sky::Vanilla { time: Some(T), sun_dir: Some(sun) } byte for byte on the CPU. Cases: quick at 12800 and 18000; HQ Game at 12800 and 18000; HQ ByTime at 12800. The same stated sky with no tick must draw something different, which proves the tick is not vacuous.
• a_stated_sky_at_no_tick_draws_as_0_2_0_did (lumenwright-compat/tests/stated_sky.rs) renders one request through this tree and through lumenwright =0.2.0 as published on crates.io. The world's DayTime is midnight. Quick and HQ must be byte-identical on the CPU.
• lumenwright-compat is a new workspace member with publish = false. A published crate cannot depend on lumenwright 0.2.0 under two names (cargo publish --dry-run refused it), so the oracle lives in its own crate. cargo test --workspace runs it, and the package job skips it.

Red before, green after. Each perturbation below was applied to a scratch copy of the tree:

perturbation	test that reds
no celestials at a stated tick	tick test: quick ByTime at 12800
stated weight fixed at 1	tick test: HQ Game at 12800
environment sampled at the world's DayTime	tick test: quick ByTime at 12800
celestials drawn at no tick	0.2.0 test, quick (and a_stated_sky_is_drawn_as_given)
ByTime as the default look at no tick	0.2.0 test, HQ

The treehouse dusk reference through the stated path

Camera: 140,118,14 looking at 56,82,58, fov 60, render distance 12, tick 12800, HQ, 8 bounces. Rendered on Apple M2 Pro Metal at 2048 spp. The stated sky is QuickSkyColours::vanilla plus sky::hq_sky at the environment's sun, StatedTick::new(12800, ByTime).

• Stated frame against Sky::Vanilla { time: Some(12800), sun_dir: None } at the same budget: byte-identical, 0 of 921 600 pixels differ.
• Both against the approved docs/renders/treehouse-camp-dusk-hq.png (CUDA, 16 384 spp): mean |d| 1.83/255.

Measured with measure.py:

method	approved reference	stated path	Chunky's look (--sky chunky)
A, sky band near the horizon	(188,125,77), hue 25.9°	(188,125,77), hue 25.9°	(241,214,120), hue 46.6°
A, sky upper left	(161,107,86), hue 16.8°	(161,107,86), hue 16.8°	(157,153,119), hue 53.7°
B, top third	mode 20–30°, 74.5% orange, 5.3% yellow	mode 20–30°, 74.8% orange, 5.5% yellow	mode 40–50°, 1.8% orange, 81.1% yellow
B, whole frame	mode 20–30°, 34.6% orange	mode 20–30°, 34.8% orange	mode 90–100°, 6.6% orange

Not expressed

Weather: the game's look draws a clear sky, both under Sky::Vanilla and at a stated tick, and applies no rain or thunder. This is recorded in CHANGELOG [Unreleased].

Docs

• CHANGELOG [Unreleased]
• docs/library.md: the stated tick
• docs/SCOPE.md: G10
• docs/testing.md: the release tests

🤖 Generated with Claude Code

https://claude.ai/code/session_016ba8LkuKW2bd5C5HCDo7p2