refactor(sky): cut what the sky does not need

- qa-anime-sky keeps only the Milky Way case; the satellites and keyless
  cases checked an anime shader this branch no longer changes.
- Drop qa-sky-sun-moon.mjs: the viewer-options unit test covers it.
- VisualEffects sets the sky's visibility directly: the viewer always
  carries a StarrySky and never outlives the effects.
- Drop the unused star intensity knob, the malformed-row tolerance for
  our own pack, the test-only Transforms parameter and a private-name test.
- DATA_SOURCES points to sky/README.md instead of repeating it.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/sky/starrySky.js

@@ -4,30 +4,16 @@ import { governorRequestRender } from '../renderGovernor.js';
 import { buildStarVertices, STAR_VERTEX_FLOATS } from './stars.js';
 
 /**
- * Space background: catalogue stars drawn as point sprites over a soft Milky
- * Way cube map, replacing Cesium's default Tycho-2 sky box (six 1024² JPEGs
- * stretched 3–6× on screen, which read as compression blocks around the
- * globe).
- *
- * Narrow, version-tested engine adapter. It takes the `Scene#skyBox` slot:
- * Cesium calls `update(frameState, useHdr)` once per frame and executes the
- * returned command first in the environment pass, before the atmosphere, sun,
- * moon and every globe or tile command — so the sky stays behind everything
- * without depth testing. Only `execute()` and `derivedCommands` of that
- * command are read. An engine upgrade must revalidate this adapter.
- *
- * Both layers share one ICRF→Earth-fixed rotation (IAU 2006 precession,
- * nutation and Earth rotation at the scene clock), so stars and the Milky
- * Way agree with each other and with the real sky over the globe. Until
- * Cesium's ICRF tables load, the TEME approximation the default sky box uses
- * fills in; the arrival renders one frame through the idle governor.
+ * Space background in the `Scene#skyBox` slot: catalogue stars as point
+ * sprites over a soft Milky Way cube map, both turned by one ICRF→fixed
+ * rotation at the scene clock (TEME until Cesium's tables load). Scene runs
+ * the command from `update()` first in the environment pass, so the sky
+ * stays behind everything without depth. Revalidate on engine upgrades.
  */
 export const STARRY_SKY_CESIUM_VERSION = '1.138.0';
 
 /** Opacity of the Milky Way glow over black; the stars carry the sky. */
 export const MILKY_WAY_INTENSITY = 0.4;
-/** Overall star brightness multiplier. */
-export const STAR_INTENSITY = 1;
 /** Clock change, in seconds, below which the sky rotation is reused. */
 export const SKY_ROTATION_EPSILON_SECONDS = 1;
 
@@ -118,14 +104,13 @@ void main()
 `;
 
 const STAR_FS = `
-uniform float u_intensity;
 in vec4 v_color;
 in float v_sigma;
 in float v_radius;
 void main()
 {
     vec2 offset = (gl_PointCoord - 0.5) * (2.0 * v_radius);
-    float alpha = v_color.a * u_intensity *
+    float alpha = v_color.a *
         exp(-0.5 * dot(offset, offset) / (v_sigma * v_sigma));
     if (alpha < 1.0 / 512.0) discard;
     out_FragColor = vec4(czm_gammaCorrect(v_color.rgb) * alpha, alpha);
@@ -133,15 +118,12 @@ void main()
 `;
 
 /** Pick the ICRF→fixed rotation for `time`, or TEME while tables load. */
-export function computeSkyRotation(
-  time,
-  result,
-  transforms = Cesium.Transforms,
-) {
-  const icrf = transforms.computeIcrfToFixedMatrix(time, result);
+export function computeSkyRotation(time, result) {
+  const { Transforms } = Cesium;
+  const icrf = Transforms.computeIcrfToFixedMatrix(time, result);
   if (icrf) return { matrix: icrf, precise: true };
   return {
-    matrix: transforms.computeTemeToPseudoFixedMatrix(time, result),
+    matrix: Transforms.computeTemeToPseudoFixedMatrix(time, result),
     precise: false,
   };
 }
@@ -169,7 +151,6 @@ export class StarrySky {
     this.milkyWayIntensity = MILKY_WAY_INTENSITY;
     /** 0..1 multiplier a style sets to hide the glow (see visualEffects.js). */
     this.milkyWayVisibility = 1;
-    this.starIntensity = STAR_INTENSITY;
     this._requestRender = requestRender;
     this._rotation = Cesium.Matrix3.clone(Cesium.Matrix3.IDENTITY);
     this._rotationTime = undefined;
@@ -197,10 +178,7 @@ export class StarrySky {
       u_milkyWay: () => this._milkyWayCubeMap,
       u_intensity: () => this.milkyWayIntensity * this.milkyWayVisibility,
     };
-    this._starUniforms = {
-      ...uniforms,
-      u_intensity: () => this.starIntensity,
-    };
+    this._starUniforms = uniforms;
     const commands = [];
     this._commands = commands;
     // The environment pass reads `derivedCommands` (log depth, HDR, picking)

src/sky/starrySky.test.mjs

@@ -25,19 +25,25 @@ test('the ICRF rotation is preferred and TEME fills in while tables load', () =>
   const time = Cesium.JulianDate.fromIso8601('2026-10-19T00:00:00Z');
   const icrf = Cesium.Matrix3.fromRotationZ(0.3);
   const teme = Cesium.Matrix3.fromRotationZ(0.2);
-  const precise = computeSkyRotation(time, new Cesium.Matrix3(), {
-    computeIcrfToFixedMatrix: (_, result) => Cesium.Matrix3.clone(icrf, result),
-    computeTemeToPseudoFixedMatrix: () => assert.fail('TEME not needed'),
-  });
-  assert.equal(precise.precise, true);
-  assert.ok(Cesium.Matrix3.equals(precise.matrix, icrf));
-  const approximate = computeSkyRotation(time, new Cesium.Matrix3(), {
-    computeIcrfToFixedMatrix: () => undefined,
-    computeTemeToPseudoFixedMatrix: (_, result) =>
-      Cesium.Matrix3.clone(teme, result),
-  });
-  assert.equal(approximate.precise, false);
-  assert.ok(Cesium.Matrix3.equals(approximate.matrix, teme));
+  const { Transforms } = Cesium;
+  const original = { ...Transforms };
+  try {
+    Transforms.computeIcrfToFixedMatrix = (_, result) =>
+      Cesium.Matrix3.clone(icrf, result);
+    Transforms.computeTemeToPseudoFixedMatrix = () =>
+      assert.fail('TEME not needed');
+    const precise = computeSkyRotation(time, new Cesium.Matrix3());
+    assert.equal(precise.precise, true);
+    assert.ok(Cesium.Matrix3.equals(precise.matrix, icrf));
+    Transforms.computeIcrfToFixedMatrix = () => undefined;
+    Transforms.computeTemeToPseudoFixedMatrix = (_, result) =>
+      Cesium.Matrix3.clone(teme, result);
+    const approximate = computeSkyRotation(time, new Cesium.Matrix3());
+    assert.equal(approximate.precise, false);
+    assert.ok(Cesium.Matrix3.equals(approximate.matrix, teme));
+  } finally {
+    Object.assign(Transforms, original);
+  }
 });
 
 test('the TEME fallback keeps the celestial pole on the Earth axis', () => {
@@ -127,11 +133,3 @@ test('the Milky Way glow scales with its visibility, for styles that hide it', (
   assert.equal(sky._milkyWayUniforms.u_intensity(), 0);
   sky.destroy();
 });
-
-test('the Milky Way stays out of the environment map that lights models', () => {
-  // Scene#render hands `skyBox._cubeMap` to image-based lighting, which
-  // expects Cesium's own TEME, flipY layout; this ICRF map would be rotated.
-  const sky = new StarrySky({ requestRender: () => {} });
-  assert.equal('_cubeMap' in sky, false);
-  sky.destroy();
-});

src/sky/stars.js

@@ -109,38 +109,17 @@ export function bvToRgb(bv) {
   return rgb.map((channel) => channel / peak);
 }
 
-/**
- * Decode a catalogue pack into interleaved vertex data, `STAR_VERTEX_FLOATS`
- * per star. Malformed rows are skipped, never thrown on: a damaged pack must
- * not take the globe down with it.
- */
-export function buildStarVertices(pack) {
-  const stars = Array.isArray(pack?.stars) ? pack.stars : [];
-  const count = Math.floor(stars.length / 4);
+/** Decode a catalogue pack into interleaved vertex data, `STAR_VERTEX_FLOATS` per star. */
+export function buildStarVertices({ stars }) {
+  const count = stars.length / 4;
   const vertices = new Float32Array(count * STAR_VERTEX_FLOATS);
-  let written = 0;
   for (let i = 0; i < count; i++) {
     const [raDeg, decDeg, vmag, bv] = stars.slice(i * 4, i * 4 + 4);
-    if (
-      !Number.isFinite(raDeg) ||
-      !Number.isFinite(decDeg) ||
-      !Number.isFinite(vmag)
-    )
-      continue;
-    const [x, y, z] = raDecToUnitVector(raDeg, decDeg);
     const { sigmaPx, alpha } = starAppearance(vmag);
-    const [r, g, b] = bvToRgb(bv);
     vertices.set(
-      [x, y, z, sigmaPx, r, g, b, alpha],
-      written * STAR_VERTEX_FLOATS,
+      [...raDecToUnitVector(raDeg, decDeg), sigmaPx, ...bvToRgb(bv), alpha],
+      i * STAR_VERTEX_FLOATS,
     );
-    written += 1;
   }
-  return {
-    count: written,
-    vertices:
-      written === count
-        ? vertices
-        : vertices.slice(0, written * STAR_VERTEX_FLOATS),
-  };
+  return { count, vertices };
 }

src/sky/stars.test.mjs

@@ -82,9 +82,9 @@ test('B−V colours run from blue-white to orange with the peak channel at 1', (
   assert.deepEqual(bvToRgb(9), bvToRgb(2));
 });
 
-test('vertex data is interleaved per star and skips malformed rows', () => {
+test('vertex data is interleaved per star', () => {
   const { count, vertices } = buildStarVertices({
-    stars: [0, 0, 1, 0.5, 'bad', 10, 2, 0, 90, 45, 3, null, 10, 20],
+    stars: [0, 0, 1, 0.5, 90, 45, 3, null],
   });
   assert.equal(count, 2);
   assert.equal(vertices.length, 2 * STAR_VERTEX_FLOATS);
@@ -93,10 +93,6 @@ test('vertex data is interleaved per star and skips malformed rows', () => {
   close(vertices[STAR_VERTEX_FLOATS + 2], Math.SQRT1_2, 1e-6);
   close(vertices[3], starAppearance(1).sigmaPx, 1e-6);
   close(vertices[7], starAppearance(1).alpha, 1e-6);
-  assert.deepEqual(buildStarVertices(null), {
-    count: 0,
-    vertices: new Float32Array(0),
-  });
 });
 
 test('the committed catalogue holds the Yale Bright Star Catalogue', () => {