ADR-0038: Resolved stars and diffuse sky share one population and dust field

Status: accepted · 7 Sep 2026

Supersedes the population-preview restriction and initial cache configuration in ADR-0032. Its source conventions, linear photometry and historical M1–M6 measurements remain recorded there. ADR-0037 continues to own camera processing.

Context

A fixed local survey does not cover the stars visible from a distant observer. Increasing its radius generates too many faint systems, and increasing its sprite ceiling makes every camera translation rewrite more positions. Drawing those sources over the integrated stellar field also counts their light twice.

Dust must end at each star. A background sky column would obscure foreground stars, while applying an observer-to-star column directly to a catalog's observed magnitude would count the Solar observer's extinction a second time. Sixteen integration samples miss thin and nearby clouds. Starting a new cache cycle on every observer movement prevents any distant column from completing.

The physical sky needs more than a settled-image hold. Free look can reuse an angular field, translation can invalidate it, and long rays still cost several milliseconds. A finished cube is expensive enough to keep across a reload, but it is regenerable data and does not belong in a save. Fine temporal detail must survive after the eye stops; clamping a stationary history to a coarse current ray erases the detail that preceding phases already measured.

Decision

Generate resolved sources from disjoint luminosity bands of the calibrated field, subtract their expected emission from the diffuse field, and transport both through the same dust.

Nine logarithmic Johnson V luminosity bands own independent (level, cell) seeds. Their number weights reproduce each population's calibrated mean V luminosity. Cell widths double from 20 light-years; luminosity bounds grow by four, so a magnitude query can bound the cells relevant to each level. Travel queries remain independent of the sky draw. New Q system addresses identify these levels; old P addresses retain their legacy generation path.

The shipped sky query requests unextinguished V ≤ 8, at most 100,000 sprites, one million candidates and 2,000 cells. Budget pressure lowers the requested magnitude or omits whole levels; it cannot pretend an unfinished level is complete. The returned selection origin, actual magnitude threshold and level mask define the diffuse subtraction. Luminosity moments remove the expected emission of exactly those bands. Omitted levels remain diffuse. This conserves ensemble light; individual stochastic realizations retain finite sampling noise and do not guarantee identical radiance in every pixel.

Catalog completeness is a magnitude-and-distance envelope, independent of search UI. Known faint neighbors remain protected inside 25 light-years; Hipparcos supplies a conservative V 7.3 envelope inside 150 light-years and the shipped distant sky supplies V 6.5 beyond it. Sparse catalog counts outside the complete envelope reduce the corresponding procedural cell and band. Catalog records retain their measured identities and flux convention.

A pending survey retains the completed source field and its exact diffuse selection envelope, including a completed empty exterior field. The next reply replaces both atomically. Only a new world publishes the initial catalog fallback. Catalog candidates and completeness coverage are derived once per world. The version 2 sky-task response carries only source identity, name, position, color and the two luminosities the renderer consumes. Other system queries retain their full records.

A source upload carries integer sectors, integer 1,024 m subcells and bounded float remainders. Observer uniforms produce directions in the vertex stage; ordinary translation uploads no source positions. Stable IDs preserve previous coordinates through reorder and rebasing. Per-source motion flags distinguish a moving source from a new source. Retained names and appearance update only where the selection changes. Enhanced's visibility response uses transported absolute V, so a different brightest star cannot brighten every other sprite.

The resolved-star dust cache integrates only to the source. It uses 32 samples through 64 pc, 64 through 512 pc and 512 for longer paths, concentrating work around the shared warped dust plane. A catalog source uses T(observer, source) / T(Sol, source); a procedural source uses the full current transmission. At Sol the catalog correction is exactly unity. Optical-depth storage preserves strongly obscured channels, with an explicit finite gain ceiling for catalog corrections.

A frozen observer starts each finite update cycle. Its queue completes before another cycle starts, including during continuous travel. Unchanged sources retain their last physical column until its replacement arrives; new sources begin hidden. Six submissions interpolate old and new optical depths. WebGPU updates at most 1,024 sources per submission; the WebGL CPU fallback updates one. The latter converges slowly during large moves and reports that lag. Source IDs, field versions and queue epochs prevent stale work from attaching to a reused buffer slot. One renderer shares one 2,048² RG16F arm table between resolved transport and diffuse light; reference-counted leases own its lifetime.

The optically young population

The active revisions are galaxy@5 and galaxy-field@5. The GPU port is galaxy-tsl@9. The signed bar coordinates use multiplication for fourth powers, because native shader pow has no defined result for a negative base. The kernel revision invalidates physical cubes computed under that undefined operation. This field corrects the earlier use of a 19 pc height for all young stellar light. Reid et al. 2019 measures that height for very young high-mass maser tracers within 7 kpc. Natale et al. 2022 models geometric young stellar components with a broader, flaring sech² distribution.

The shared height is H(R) = 50 + 17 (R / 4500)^p pc, where p = log(40/17) / log(8178/4500). It reaches 50 pc at the center, 67 pc at 4.5 kpc and 90 pc at the Sun. The vertical factor is (50 / H) sech²((y − warp) / H), preserving the column as height changes. Applying that geometric profile to our arm ridges, and continuing its flare beyond the Sun, are declared model assumptions. The radial exponential, arm positions, dust, old populations and seeded texture remain unchanged.

The effective mean solar V luminosities are 0.204 for the thin disk, 0.35 for the thick disk, 100 for young arms, 0.7725 for the bar/bulge and 0.1 for the halo. Thin and bulge means are fitted against the same three Solar sky regions and external V luminosity; these are population-model means, not measured individual-star luminosity functions. The default-seed V residuals are +0.0765, +0.1785, −0.2800 and +0.0325 mag respectively, within the original 0.3 mag limits. Local number density remains 0.1 star/pc³ and the reference cylinder contains 116.064 billion stars. Catalog-plus-procedural counts in 10, 25 and 50 pc balls around Sol are 389, 6,788 and 53,532, against field integrals of 418.924, 6,549.357 and 52,109.668 — −7.14%, +3.64% and +2.73%. Those are counts of one finite realization against the smooth integral it is drawn from, not a second calibration target. The finer quadrature retains its original convergence test.

The young cohort contributes 15.31% of emergent ridge V at solar radius, compared with 0.66% in the tracer-height model. This is a modest improvement to the external arms. The model's large central V luminosity fraction remains an approximation; a published stellar-mass bulge fraction is not a V-light constraint. RGB temperatures are illustrative and do not establish a Johnson B−V calibration. No display response enters the physical fit.

The saved manifest identifies generation drift. Q addresses encode a level/cell/ordinal, so they can change under a different recorded generation version; an ordinal that no longer exists fails explicitly. The unpublished galaxy@4 level population receives that existing drift policy. Old P destinations continue to use their exact legacy generator.

Physical cubes and temporal history

Ordinary nearby views refine complete 32², 128² and 512² cubemaps. The three tiers hold 6, 96 and 1,536 tiles of 32×32 pixels; two are submitted per frame, so a complete refinement submits 1,638 of them. The boot census ends after the 128² tier, while the 512² tier continues in the background. Each cube uses a conservative 2/N radian angular texel footprint; the projection reaches that width at face centers. The archive fingerprint includes this filtering revision. Three target slots retain two completed locations and one replacement. Only six complete faces publish. Canceled work, changed fields or source partitions, renderer retirement and late storage reads cannot publish into a different generation.

Cube reuse is limited to 0.15 pc, measured against local cloud gradients. A disk-restored source envelope can have a slightly different origin, so envelope displacement and eye displacement spend one combined allowance. The restored entry retains the remaining eye allowance for all later reuse. Magnitude or level-mask changes reject the entry. A mode, lens, exposure or display-gamut change does not change physical sky light.

The regenerable IndexedDB store retains at most two finished cubes in a separate database. Records contain a versioned field fingerprint, kernel and backend, quality, observer and source envelope, and all six physical RGBA16F faces. Reads validate metadata, finite nonnegative radiance and complete faces. Pixel validation yields every 16,384 texels; restoration checks its request identity again after validation. Database version 2 separates small LRU metadata from pixel payloads: eviction enumerates keys, and a hit touches metadata without rewriting its cube. Upgrading retires the regenerable version 1 cache once. Writes wait for transaction completion. Unsupported, blocked or failed storage is a cache miss. GPU readback and upload preserve native cube-face orientation and padded row strides; temporary transfer textures are disposed.

Outside the nearby disk, or beyond a valid cube, live rays fill half-resolution physical history using an eight-by-eight interleaved pattern. At 1920×1080 this traces 120×68 primary rays per submission and retains 960×540 history. Production caps the history's longest edge at 960 pixels, preserving aspect ratio and at least the half-resolution divisor on smaller displays. A 2880×1800 drawing buffer therefore retains 960×600 and traces 120×75 rays. Reference instruments can leave this cap unset. Warmup and resize use the same sizing calculation. RGB remains V-anchored nW m⁻² sr⁻¹ divided by 1,000; alpha carries emission-weighted distance for reprojection. Foreground occlusion remains in the full-resolution scene.

History rejects camera cuts, large parallax, disocclusion, changed fields or source partitions, resize and renderer retirement. Moving history is bounded by current neighboring radiance; stationary history retains already measured fine samples. Exposure does not invalidate physical history. After the eye settles and every phase completes, the target is held until something changes.

Alternatives considered

Generate a larger uniform local survey. Faint stars dominate its work and memory before its visible reach approaches the galaxy. The sky and travel catalog answer different queries.

Subtract the whole population inside a distance sphere. Bright distant sources and faint nearby sources cross that sphere differently. Luminosity bands permit the same selection rule in source generation and diffuse transport.

Normalize sprite appearance to the currently brightest source. A replacement selection changes the rest of the sky's brightness. Absolute transported V provides a stable response and removes GPU maximum reductions.

Use sixteen dust samples or restart them on movement. The first misses physical columns; the second starves a moving observer's queue. Distance-aware quadrature and finite cycles bound the work without discarding foreground dust.

Persist generated stars or put cubes in saves. Both can be regenerated. A small independent cache improves reload cost without changing canonical state or making save compatibility depend on a GPU texture.

Clamp every history sample. The coarse current grid has not measured the fine stationary feature it is clamping. Restricting that clamp to motion keeps its ghost-rejection purpose without erasing converged angular detail.

Consequences

The active population spends a generation version. Legacy procedural addresses remain resolvable, while new selection and portable-picture manifests identify the active algorithm. The source model and camera response remain independently inspectable and tested.

The 100,000-source capacity reserves about 21.2 MB of GPU source, appearance and dust data, in addition to the shared 16 MiB arm table. The dust cache allocates 10,004,096 bytes on WebGPU or 3,200,000 attribute bytes on the CPU fallback, never both sets. These figures exclude the CPU slot lookup and scheduling maps. A 512² physical cube is 12 MiB. Half-resolution temporal resources add 9.33 MB over the measured quarter-resolution alternative at 1080p. These are declared allocations, excluding driver overhead and temporary JavaScript generation memory.

The live 2 ms target is not a universal bound. The performance plan names the measured operating points and the chosen quality budget. Typical retained source replacement fits 5 ms of main-thread preparation; cold entirely new populations and garbage collection can exceed it. GPU source updates and diffuse cache refinement are bounded separately from worker generation.

The field still uses illustrative RGB stellar colors and absorption-only dust. Scattering, H II line emission, globular clusters and neighboring galaxies are separate physical additions. Finite source realizations, angular interpolation, and delayed moving-star dust refresh are observable approximation limits.