perf(points): shrink VSOut + per-instance buffer

src/@types/animation/FadeHandle.d.ts

@@ -21,7 +21,7 @@
  *                    galaxy names, scale bar). Discriminator:
  *                    `layer: LabelLayerId`.
  *   - overlay      — always-on GPU overlay (Milky Way, procedural
- *                    disks, textured impostors). Registered at
+ *                    disks, textured disks). Registered at
  *                    opacity 1.0 via setImmediate. Discriminator:
  *                    `id: OverlayId`.
  *   - volumesMaster — the master enable gate for the whole scalar-

src/@types/animation/OverlayId.d.ts

@@ -11,6 +11,6 @@
  *   - milkyWay         — single-quad procedural Milky Way impostor.
  *   - proceduralDisks  — LOD-1 procedural-disk pass (per-galaxy disk
  *                        impostor for the close-approach band).
- *   - texturedImpostors — LOD-2 textured-thumbnail quad pass.
+ *   - texturedDisks — LOD-2 textured-thumbnail quad pass.
  */
-export type OverlayId = 'milkyWay' | 'proceduralDisks' | 'texturedImpostors';
+export type OverlayId = 'milkyWay' | 'proceduralDisks' | 'texturedDisks';

src/@types/engine/BuildPointInterleavedBufferInput.d.ts

@@ -9,7 +9,7 @@ export type BuildPointInterleavedBufferInput = {
   source: Source;
   /**
    * Whether to compute the per-galaxy Schechter ratios as part of this bake.
-   * Defaults to `'fast'` (slot 10 = 1.0).  See `BuildPointInterleavedBufferMode`
+   * Defaults to `'fast'` (slot 9 = 1.0).  See `BuildPointInterleavedBufferMode`
    * for the trade-off.  Optional so existing callers (and the worker
    * structured-clone roundtrip) keep working without recompilation.
    */

src/@types/engine/BuildPointInterleavedBufferMode.d.ts

@@ -2,14 +2,14 @@
  * BuildPointInterleavedBufferMode — selector for the bake's
  * Schechter-ratio strategy.
  *
- *   - `'fast'` — slot 10 (per-vertex `schechterRatio`) is filled with 1.0,
+ *   - `'fast'` — slot 9 (per-vertex `schechterRatio`) is filled with 1.0,
  *                so the shader's bias-mode branch is a no-op when None /
  *                VolumeLimited / V_max are selected.  All three modes
- *                ignore slot 10 anyway, so this is correct AS LONG AS the
+ *                ignore slot 9 anyway, so this is correct AS LONG AS the
  *                user hasn't picked Schechter LF.  This is the default at
  *                upload time — the .bin lands fast (~2 s saved on a
  *                fully-loaded deck).
- *   - `'with-schechter'` — slot 10 holds the real `min(1, sqrt(nRef/n(d)))`
+ *   - `'with-schechter'` — slot 9 holds the real `min(1, sqrt(nRef/n(d)))`
  *                          ratio, computed via `computeSchechterRatios`.
  *                          Used either when an upload happens *while*
  *                          Schechter mode is already active, or as part

src/@types/engine/ReadyEngineState.d.ts

@@ -18,7 +18,7 @@ import type { PointRenderer } from '../rendering/PointRenderer';
 import type { PickRenderer } from '../rendering/PickRenderer';
 import type { PostProcess } from '../rendering/PostProcess';
 import type { VolumeOffscreen } from '../rendering/VolumeOffscreen';
-import type { TexturedImpostorSubsystem } from './subsystems/TexturedImpostorSubsystem';
+import type { TexturedDiskSubsystem } from './subsystems/TexturedDiskSubsystem';
 
 export type ReadyEngineState = EngineState & {
   cam: OrbitCamera;
@@ -36,6 +36,6 @@ export type ReadyEngineState = EngineState & {
     volumeOffscreen: VolumeOffscreen;
   };
   subsystems: EngineState['subsystems'] & {
-    texturedImpostors: TexturedImpostorSubsystem;
+    texturedDisks: TexturedDiskSubsystem;
   };
 };

src/@types/engine/frame/ReadyFrameContext.d.ts

@@ -53,7 +53,7 @@ import type { Vec3 } from '../../math/Vec3';
 import type { PointRenderer } from '../../rendering/PointRenderer';
 import type { PostProcess } from '../../rendering/PostProcess';
 import type { VolumeOffscreen } from '../../rendering/VolumeOffscreen';
-import type { TexturedImpostorSubsystem } from '../subsystems/TexturedImpostorSubsystem';
+import type { TexturedDiskSubsystem } from '../subsystems/TexturedDiskSubsystem';
 
 /** The ready case: every per-frame derived value is non-null. */
 export type ReadyFrameContext = {
@@ -85,5 +85,5 @@ export type ReadyFrameContext = {
    * `ctx.volumeOffscreen.view` without reaching back into `state`.
    */
   volumeOffscreen: VolumeOffscreen;
-  texturedImpostors: TexturedImpostorSubsystem;
+  texturedDisks: TexturedDiskSubsystem;
 };

src/@types/engine/handles/EngineSubsystemHandles.d.ts

@@ -21,7 +21,7 @@
  *     `scheduler`.  None of these need a GPU device — their callbacks
  *     queue work that the scheduler will pick up once the IIFE finishes.
  *   - Lazy (inside the IIFE): `galaxyAtlas` / `proceduralDisks` /
- *     `texturedImpostors` (need the GPU device + the
+ *     `texturedDisks` (need the GPU device + the
  *     TexturedQuadRenderer / TexturedDiskRenderer pair), `clickResolver`
  *     (needs the pick renderer), `inputBindings` (needs the scheduler so
  *     it can wake the loop on input).  These start as null.
@@ -39,7 +39,7 @@
 
 import type { GalaxyAtlasSubsystem } from '../subsystems/GalaxyAtlasSubsystem';
 import type { ProceduralDiskSubsystem } from '../subsystems/ProceduralDiskSubsystem';
-import type { TexturedImpostorSubsystem } from '../subsystems/TexturedImpostorSubsystem';
+import type { TexturedDiskSubsystem } from '../subsystems/TexturedDiskSubsystem';
 import type { SpaceMouseSubsystem } from '../subsystems/SpaceMouseSubsystem';
 import type { SelectionSubsystem } from '../subsystems/SelectionSubsystem';
 import type { BiasCorrectionSubsystem } from '../subsystems/BiasCorrectionSubsystem';
@@ -57,7 +57,7 @@ import type { Destroyable } from '../../rendering/Destroyable';
 export type EngineSubsystemHandles = {
   galaxyAtlas: GalaxyAtlasSubsystem | null;
   proceduralDisks: ProceduralDiskSubsystem | null;
-  texturedImpostors: TexturedImpostorSubsystem | null;
+  texturedDisks: TexturedDiskSubsystem | null;
   spaceMouse: SpaceMouseSubsystem;
   tweens: TweenManager;
   clickResolver: ClickResolver | null;

src/@types/engine/subsystems/GalaxyAtlasSubsystem.d.ts

@@ -1,20 +1,20 @@
 /**
  * GalaxyAtlasSubsystem — shared GPU texture atlas + bitmap-fetch queue
- * for the LOD-2 (textured-impostor) galaxy path.
+ * for the LOD-2 (textured-disk) galaxy path.
  *
  * ### What this owns
  *
  * The 2048² LRU atlas texture, the LRU clock, the priority-queued bitmap
  * fetcher, failure memoisation, and an eviction notification hook.  It
  * has NO direct connection to per-frame catalog walking — that lives in
- * `texturedImpostorSubsystem`, which calls into this atlas to allocate
+ * `texturedDiskSubsystem`, which calls into this atlas to allocate
  * slots and schedule fetches.
  *
  * ### Why a separate subsystem
  *
  * Pre-split, this state lived inline in `thumbnailSubsystem` alongside
  * per-frame planning + render dispatch.  Splitting it out gives the LOD-2
- * planner (`texturedImpostorSubsystem`) one focused dependency to inject
+ * planner (`texturedDiskSubsystem`) one focused dependency to inject
  * — and gives future code that wants to read atlas state (debug HUD,
  * memory profilers) a typed surface to consume.
  *
@@ -68,7 +68,7 @@ export type GalaxyAtlasSubsystem = Destroyable & {
   isFailed(key: string): boolean;
 
   /**
-   * Number of in-flight fetches.  Read by the textured-impostor
+   * Number of in-flight fetches.  Read by the textured-disk
    * subsystem's `hasInFlightWork()` (which the engine's render-on-demand
    * predicate ORs in).
    */
@@ -79,7 +79,7 @@ export type GalaxyAtlasSubsystem = Destroyable & {
 
   /**
    * Optional handler called when LRU evicts a slot.  The
-   * `texturedImpostorSubsystem` subscribes to clear its bitmapReady /
+   * `texturedDiskSubsystem` subscribes to clear its bitmapReady /
    * bitmapFailed / bitmapReadyTime entries for the ousted key.
    */
   setEvictHandler(handler: ((key: string) => void) | undefined): void;

src/@types/engine/subsystems/PoiSubsystem.d.ts

@@ -31,7 +31,7 @@ export type PoiSubsystem = LabelProducer & {
    * markers (halo + ring).  Returns one descriptor per visible POI
    * after applying the apparent-size fade-in band AND the
    * max-apparent-radius fade-out.  Famous-galaxy POIs always return
-   * empty (they render through the textured-impostor + label paths).
+   * empty (they render through the textured-disk + label paths).
    *
    * The producer never mutates engine state directly — the returned
    * array is fed to `state.gpu.clusterMarkerRenderer.setMarkers(...)`

src/@types/engine/subsystems/TexturedImpostorSubsystem.d.ts → src/@types/engine/subsystems/TexturedDiskSubsystem.d.ts

@@ -1,5 +1,5 @@
 /**
- * TexturedImpostorSubsystem — LOD-2 per-frame planner.
+ * TexturedDiskSubsystem — LOD-2 per-frame planner.
  *
  * Walks the catalog, applies the px ≥ 24 fetch gate, allocates atlas
  * slots through the injected `GalaxyAtlasSubsystem`, schedules fetches,
@@ -25,23 +25,23 @@ import type { OrbitCamera } from '../../camera/OrbitCamera';
 import type { FamousMetaEntry } from '../../loading/FamousMetaEntry';
 import type { Source } from '../../../data/sources';
 
-export type TexturedImpostorFrameInput = {
+export type TexturedDiskFrameInput = {
   readonly cam: OrbitCamera;
   readonly catalogs: ReadonlyMap<Source, GalaxyCatalog>;
   readonly visibleSourceMask: number;
   readonly pxPerRad: number;
   readonly famousMeta: readonly FamousMetaEntry[];
 };
 
-export type TexturedImpostorFrameOutput = {
+export type TexturedDiskFrameOutput = {
   /** LOD-2 — galaxies with finite orientation, sorted back-to-front. */
   readonly disks: readonly DiskInstance[];
 };
 
-export type TexturedImpostorSubsystem = Destroyable & {
-  runFrame(input: TexturedImpostorFrameInput): TexturedImpostorFrameOutput;
+export type TexturedDiskSubsystem = Destroyable & {
+  runFrame(input: TexturedDiskFrameInput): TexturedDiskFrameOutput;
 
-  readonly lastOutput: TexturedImpostorFrameOutput;
+  readonly lastOutput: TexturedDiskFrameOutput;
 
   /**
    * OR'd into the engine's render-on-demand predicate.  True while any
@@ -56,10 +56,10 @@ export type TexturedImpostorSubsystem = Destroyable & {
  * shape the legacy thumbnailSubsystem did, so the split-out tests can
  * inspect the post-extraction subsystem's bookkeeping the same way.
  */
-export type TexturedImpostorTestState = {
+export type TexturedDiskTestState = {
   readonly bitmapReadyTime: ReadonlyMap<string, number>;
 };
 
-export type TexturedImpostorSubsystemWithTestSeam = TexturedImpostorSubsystem & {
-  __testGetState(): TexturedImpostorTestState;
+export type TexturedDiskSubsystemWithTestSeam = TexturedDiskSubsystem & {
+  __testGetState(): TexturedDiskTestState;
 };

src/@types/gpu/timing/TimingSlotName.d.ts

@@ -17,12 +17,8 @@
  * future inhabitants without forcing a query-set resize.
  *
  * The strings match the `name` fields on `Pass` objects (e.g.
- * `pointSpritesPass.name === 'point-sprites'`).  Tests in Task 9 lean
- * on that equality to assert each pass plumbs its timing descriptor.
- *
- * The `textured-disks` slot replaces the legacy `textured-impostors`
- * slot (2026-05-18 split + 2026-05-18 quad-removal).  Same slot
- * indices (4, 5) so historical samples stay comparable.
+ * `pointSpritesPass.name === 'point-sprites'`).  Tests lean on that
+ * equality to assert each pass plumbs its timing descriptor.
  */
 
 export type TimingSlotName =

src/@types/rendering/PointRenderer.d.ts

@@ -42,11 +42,11 @@ export type PointRenderer = {
   setBiasUploadCallback(cb: ((source: Source, cloud: GalaxyCatalog) => void) | null): void;
   /** Install the unload-tail callback for the bias-correction subsystem. */
   setBiasUnloadCallback(cb: ((source: Source) => void) | null): void;
-  /** Splice per-row Schechter ratios into slot 10 of the source's interleaved mirror. */
+  /** Splice per-row Schechter ratios into slot 9 of the source's interleaved mirror. */
   spliceSchechterRatios(source: Source, ratios: Float32Array): void;
-  /** Splice per-row HEALPix angular weights into slot 11. */
+  /** Splice per-row HEALPix angular weights into slot 10. */
   spliceAngularWeights(source: Source, weights: Float32Array): void;
-  /** Zero slots 10 + 11 for one source or every loaded source. */
+  /** Zero slots 9 + 10 for one source or every loaded source. */
   clearBiasOverlays(source?: Source): void;
   /** Total number of points across every loaded source. */
   totalCount(): number;

src/data/colourIndex.ts

@@ -15,6 +15,24 @@
 import { Source, type SurveySource } from './sources';
 import type { ColourIndexSpec } from '../@types/data/ColourIndexSpec';
 
+/**
+ * Hubble distance in Mpc — c / H₀ for H₀ = 70 km/s/Mpc. Converts
+ * Cartesian distance from origin to cosmological redshift via
+ * z = d / HUBBLE_DISTANCE_MPC, matching the small-z Hubble approximation
+ * the project's raDecZToCartesian uses to produce these positions.
+ */
+const HUBBLE_DISTANCE_MPC = 4282.749;
+
+/**
+ * Ramp-position fallback for rows whose colour cannot be computed (one
+ * or both bands missing). 1.05 is a deliberately pale, neutral position
+ * on the 0..2 ramp — close enough to the middle that sentinel rows
+ * don't draw the eye away from real colour gradients. Both the points
+ * bake and the procedural-disk subsystem substitute this value, so a
+ * galaxy without bands renders the same hue in both renderers.
+ */
+export const UNKNOWN_COLOUR_RAMP_POSITION = 1.05;
+
 // POI source codes (Cluster, Supercluster, Void) have no photometry —
 // they're pick-encoding-only markers, not survey rows. The colour-index
 // spec is therefore keyed by `SurveySource` (excludes POIs), and the
@@ -33,9 +51,16 @@ const SPEC: Record<SurveySource, ColourIndexSpec> = {
 };
 
 /**
- * Look up which slot maps to which mag value, then compute the source-
- * appropriate colour index and K coefficient. Returns null when either
- * constituent band is NaN (so the caller knows to use the sentinel path).
+ * Look up which slot maps to which mag value, compute the source-
+ * appropriate colour index, K-correct it to rest-frame using the row's
+ * distance, and normalise to the 0..2 ramp range. Returns
+ * {@link UNKNOWN_COLOUR_RAMP_POSITION} when either constituent band is
+ * NaN, so callers never need a null-check or fallback constant.
+ *
+ * The K-correction is applied here (CPU side) so both consumers
+ * (`buildPointInterleavedBuffer` and `proceduralDiskSubsystem`) get the
+ * same rest-frame value, removing a visible hue mismatch between the
+ * points pass and the procedural-disk impostor for the same galaxy.
  */
 export function pickColourIndex(
   source: Source,
@@ -44,31 +69,30 @@ export function pickColourIndex(
   magR: number,
   magI: number,
   magZ: number,
-): { colourIndex: number; kPerZ: number } | null {
+  dMpcFromOrigin: number,
+): number {
   if (source === Source.Cluster || source === Source.Supercluster || source === Source.Void) {
     throw new Error(`pickColourIndex: POI source ${source} has no colour index`);
   }
   const spec = SPEC[source as SurveySource];
   const slotMap = { u: magU, g: magG, r: magR, i: magI, z: magZ };
   const a = slotMap[spec.slotA];
   const b = slotMap[spec.slotB];
-  if (!Number.isFinite(a) || !Number.isFinite(b)) return null;
+  if (!Number.isFinite(a) || !Number.isFinite(b)) return UNKNOWN_COLOUR_RAMP_POSITION;
 
-  // ── Normalise raw colour to the 0..2 ramp range ─────────────────────────
-  //
-  // The WGSL ramp expects its input in [0, 2].  We pre-bake the linear
-  // remap here so the shader doesn't need to know any per-source range
-  // numbers — it just reads a single f32 and indexes the ramp.
-  //
-  // kPerZ is passed through unchanged: it's already specified in
-  // normalised ramp-position units (see the SPEC type's docstring for
-  // why the literature mag/z values aren't used directly).
+  // Normalise raw observed colour to the 0..2 ramp range. The WGSL ramp
+  // expects its input there; pre-baking the linear remap means the
+  // shader reads a single f32 and indexes the ramp.
   const raw = a - b;
-  const colourIndex = Math.max(
-    0,
-    Math.min(2, ((raw - spec.rangeMin) / (spec.rangeMax - spec.rangeMin)) * 2.0),
-  );
-  return { colourIndex, kPerZ: spec.kPerZ };
+  const observedCI = ((raw - spec.rangeMin) / (spec.rangeMax - spec.rangeMin)) * 2.0;
+
+  // K-correction: colour_rest ≈ colour_obs − k · z. kPerZ is already in
+  // normalised ramp-position units, so the subtraction happens directly
+  // on the ramp coordinate. Re-clamp because the correction can push
+  // the value outside [0, 2].
+  const z = dMpcFromOrigin / HUBBLE_DISTANCE_MPC;
+  const restCI = observedCI - spec.kPerZ * z;
+  return Math.max(0, Math.min(2, restCI));
 }
 
 /** Public read of the spec table — used by `galaxyType.ts` and tests. */