Mzu 3D Solar System

A free, browser-based 3D Solar System visualization built with Three.js.

• Live site: https://www.3dsolarsystem.net/
• Repository: https://github.com/sweesama/Mzu-3D-Solar-System--Interactive-Solar-System-Simulator

Product scope

The project is an artistic educational visualization. It lets visitors rotate and zoom a 3D scene, select celestial objects, view basic reference data, follow a planet tour, share focused links, save a canvas snapshot, and copy an embed snippet.

It is not a live ephemeris or a professional astronomy simulator. Object sizes, distances, orbital periods, and animation speed are adjusted for visibility. Some textures and surface details are artistic or procedural.

Run locally

Serve the repository through a local HTTP server; opening the HTML files directly may prevent browser workers or assets from loading correctly.

python -m http.server 8000

Then open http://localhost:8000/.

Useful URLs

• Focus a supported object: /?focus=Earth
• Use a lightweight embedded interface: /?focus=Earth&embed=1
• Let the site choose a profile and adapt after sustained low frame rates: /?quality=auto
• Force the balanced profile: /?quality=balanced
• Force reduced detail: /?quality=low
• Force full detail on a capable device: /?quality=high

The visible quality selector stores the visitor's preference locally. Auto mode uses available memory, CPU, viewport, pixel-density, and data-saving signals without treating every phone as low-end. It can reduce render resolution and procedural asteroid load if measured performance remains poor.

Camera focus behavior

• ?focus= and the planet navigation share one focus path: the camera flies to the object and then follows it (trackedObject), so moving bodies stay framed. Satellites keep the same close-up framing as planets (radius × 2.5); there is no separate widened framing.
• Before the first animate() frame, orbital positions have not been written yet, so initial focus runs updateOrbitalPosition() once over all bodies to place them before computing the camera destination.
• Camera transitions aim at where the object will be when the flight ends (predictWorldPosition), so fast-moving moons do not get left behind mid-flight.
• Canvas clicks ignore orbit guide lines, ignore a planet's invisible click-helper sphere when the camera is inside it, and pick the candidate the ray passes closest to relative to its size. Moons also carry small click-helper spheres (capped at 35% of their orbit radius), so they can be clicked reliably even inside a planet's own helper zone. Belt particles are only a fallback when nothing else was aimed at.

Generate planet pages

The eight planet pages are generated from index.html and factual page data:

node generate_seo_pages.cjs

Validate public output after generation:

node validate_site.cjs
node --check main.js

Never hand-edit mercury.html … neptune.html: change index.html or the data in generate_seo_pages.cjs (intro, quick facts, featured expedition card) and regenerate.

Expedition About articles (English and Chinese)

• Each expedition page's <article id="about"> holds two versions: .lang-en and .lang-zh. moon.css shows only the one matching <html lang>, which the page's language button sets. The arrival-card cue link has the same pair of spans.
• Search engines read both versions in the HTML, so the English text stays crawlable. Keep the two versions in step when facts change, since they are written by hand, not generated.

Shared expedition modules

• expedition-dust.js (ExpeditionDust.create) holds the footstep and landing dust used by the Moon, Mars, Venus and Mercury expeditions. Each page passes in its own colour, opacity, gravity, terrain sampler and optional wind drift; the spawning, arc, ground contact, fading and disposal logic lives once. Load it before the engine script.
• expedition-look.js (ExpeditionLook.applyDrag) is the drag-to-look maths used by all eight expeditions: sensitivity, yaw wrap-around and pitch limits in one place. It is a pure function, so node can check it against the old formula (the maximum difference was 0).
• Moon sun and horizon: The Sun is a bright (4x) basic sphere, so the existing bloom pass makes its glow. The Moon no longer uses the screen-space lens flare (its halo ring read as a pasted sticker). The horizon glow is a vertically oriented plane with vertex-colour falloff, not a canvas texture.

Speed control (main explorer)

• The Speed menu switches between Artistic (compressed, for easy viewing) and Real speeds at 1 hour / 1 day / 1 week / 1 month / 1 year per second. The choice is saved in localStorage (mzu-time-scale).
• Real mode uses true sidereal orbital and rotation periods from REAL_PERIODS in main.js (NASA fact sheets; tidally locked moons spin once per orbit). Bodies without table data (asteroids, comets, Kuiper objects) use Kepler's third law from their semi-major axis. Retrograde motion keeps its sign (Triton); Venus and Uranus get their backward/sideways spin from their axial tilt.
• Any motion faster than 2 turns per second is capped for display only, to avoid stroboscopic "backwards" spinning.

Scale control (main explorer)

• The Scale menu has four modes, saved in localStorage (mzu-scale-mode):
  • Artistic: the default, compressed for viewing.
  • Real distances: planets, dwarf planets, asteroids and comets orbit at their true semi-major axes, with 1 AU = AU_SCENE (40) scene units, so Neptune sits about 1,200 units out. Sizes stay enlarged.
  • Real sizes: the Sun, planets, dwarf planets and moons get their true relative radii, with distances still compressed.
  • True scale: both together. Moon orbits also switch to their real distances here (the Moon at 60 Earth radii).
• applyScaleMode() rescales orbit radii, orbit lines (scaled about the focus), body meshes (rings, clouds and atmospheres scale with their planet), the Sun and the Kuiper belt. Asteroids and comets keep their artistic size, or they would be invisible.
• When any real mode is on, each planet gets a fixed-size screen marker with its name (*_marker sprites). Clicking a marker focuses that planet, and the marker hides once you are within about 40 radii of the planet.
• The sky (real star catalogue + generated Milky Way, see "Real star sky and generated Milky Way" below) follows the camera, so they stay "at infinity" even with outer planets 1,200+ units away. In real-size modes the camera near plane shrinks with focus distance so tiny planets are not clipped.
• Camera flights (flyCameraToObject, shared by clicks and the guided tour) interpolate toward the target's live position every frame instead of a predicted end point. At true scale the camera stops only thousandths of a unit from a planet, so any prediction error would otherwise strand it far away. Flight distance is always 2.5× the body's current world radius.

Rendering notes (main explorer)

• Shadows are analytic, not shadow maps. addEclipseShadows(material, occluders) in main.js injects a shader test: from each pixel, a ray toward the Sun (world origin) is checked against up to four occluding spheres, with a soft penumbra sized by the Sun's apparent radius. Planets receive their moons' shadows, moons receive their planet's, and ring systems receive their planet's shadow. updateEclipseShadows() refreshes occluder positions every frame. The old point-light cube shadow map (jagged edges, six extra scene renders per frame) is disabled.
• Stars are round. The starfield uses a small custom ShaderMaterial that honours the per-star size attribute, clamps on-screen size (no giant squares up close), draws a soft disc via gl_PointCoord, and adds a gentle per-star twinkle. Kuiper-belt and comet-tail points use a shared soft-dot texture (getSoftDotTexture()); any new PointsMaterial should be given a map, or it will render squares.
• The Sun is styled after NASA SDO 304 Å imagery. The photosphere shader samples 3D noise on the sphere (no UV seam or pole pinching) with domain warping for a churning, fibrous chromosphere, bright plage regions, thin dark filaments, and limb brightening. Noise layers are kept to 2–4 octaves because stacking many full 6-octave fbm calls risks compile failures on some GPUs; note that active is a reserved GLSL word. The corona is a camera-facing plane (sunGlowSprite, kept by name for the occlusion logic) whose shader adds a bright inner rim, slowly outward-flowing streamers, a flickering spicule fringe at the limb, and occasional flame-like prominences.
• Planet spheres use 96×64 segments (48×48 on low quality) and moons 40×28, so silhouettes stay round when zoomed in; textures get up to 8× anisotropic filtering outside low-detail mode.

SEO and sharing

• Share images live in og/ (1200×630 JPEG): home.jpg, one per planet page (og/<planet>.jpg) and one per expedition (og/<planet>-expedition.jpg). Every page uses summary_large_image Twitter cards, og:image:width/height/alt, and the same URL as image/screenshot in its JSON-LD. To refresh an image, open the page at a 1200×630 viewport, enter photo mode (expeditions) or close the guide panel (planet pages), and screenshot.
• Crawlable expedition text: each expedition page ends with an <article id="about"> (300+ words: intro, quick facts <dl>, five discoveries, controls, science vs. art, links to its planet page and the other seven expeditions). It sits below the full-screen scene; expedition-about.js lets visitors scroll to it only while the arrival card is showing and snaps back to the top when the expedition starts. The article is English only.
• Planet pages feature their own expedition as a large card, list three quick facts, and link the remaining expeditions as compact tiles. Inside the guide panel each also has an "About" article and three FAQs (from articles in generate_seo_pages.cjs), citing NASA Science and the NASA Planetary Fact Sheet; the FAQs are mirrored as FAQPage JSON-LD. The homepage carries its own three-question FAQ between the PLANET-ARTICLE markers, which the generator swaps per planet.
• Breadcrumbs: planet pages (Home → Planet) and expedition pages (Home → Planet → Expedition) include BreadcrumbList JSON-LD.
• llms.txt summarises every page with key facts for AI search engines; keep it in step with page content.
• Analytics: all 17 pages carry the same Google Analytics tag.
• sitemap.xml lists all 17 pages with lastmod and their share image. Update lastmod when a page changes; the validator rejects future dates and missing images.
• validate_site.cjs also fails if a page falls back to the logo as its share image, if an expedition loses its About article or planet link, or if analytics are missing.

Main files

• index.html: shared page shell and visible homepage copy
• quality-policy.js: testable automatic quality selection and render profiles
• main.js: Three.js scene, interactions, runtime performance relief, and rendering
• style.css: responsive overlay and scene controls
• generate_seo_pages.cjs: deterministic planet-page generator
• validate_site.cjs: metadata, content, sitemap, and claim checks
• llms.txt and llms-full.txt: factual machine-readable product summaries

Asset and data note

The repository contains code, textures, models, and third-party runtime dependencies from multiple sources. Do not assume every file has the same reuse terms. Keep source and attribution records for any external asset before redistributing it.

Moon expedition

The public page is https://www.3dsolarsystem.net/moon.html. It is listed in sitemap.xml, linked from the homepage and generated planet pages, and includes indexable robots metadata, a canonical URL, Open Graph/Twitter cards, and WebApplication JSON-LD. Query-string preferences canonicalize to the same page; there are no separately indexed language pages. Sharing cards use the existing site logo. robots.txt already allows crawling and advertises the sitemap. These settings enable discovery but do not guarantee search-engine indexing or ranking.

Open http://localhost:8000/moon.html or use Step onto the Moon in the Solar System guide. This independent page does not load the orbital simulation. It needs no account, AI service, API key, or build step.

• A science-inspired, procedurally generated lunar region with a 300-metre walking radius; not an actual surveyed landing site or a whole-planet terrain model.
• Five observation points within the same landscape: crater overlook, boulder field, Earth viewing point, a lunar module resting on the plain, and a shadowed crater hollow. The numbered buttons offer quick travel to the first three; the last two can only be reached on foot. Arriving by quick travel does not automatically record a discovery.
• Follow the amber guide dots, direction arrow, and route distance. Walk close to a discovery and press E, click its marker, or use Discover. You must be on the ground to record a new discovery. Next stop changes the destination without moving you. After reading a discovery, Continue exploring selects the next undiscovered stop.
• The boulder discovery opens a separate 3D specimen view. Drag or use arrow keys to rotate, and use the zoom buttons to inspect it. Clicking the large featured boulder at close range also opens it. This is a representative artistic rock, not an identified sample.
• The journal counts unique discoveries from 0/5 to 5/5 and saves locally under mzu-moon-discoveries-v1. Reloading restores the journal, not the astronaut's position. If browser storage is blocked or full, discoveries still work for the current visit and the interface says they are not saved. No account or server is required.
• The amber dots are optional visual navigation aids, not physical lunar installations; photo mode hides both the route and destination marker.
• The viewpoint is an astronaut on foot, not a rover or flying camera. Click Step onto the Moon, then use WASD or arrow keys to walk, Shift for a brisker pace, and drag to look. Look down to see your boots. Touchscreens have a direction pad and Jump button.
• Space jumps from the ground. There is no double jump or automatic repeated jumping when held. Airborne movement preserves takeoff momentum; steep uphill terrain, larger rocks, and the region boundary still block passage. Landing and uneven terrain are handled against the rendered ground.
• Walking leaves alternating boot prints on the regolith, and jumps kick up dust that falls back along ballistic arcs — there is no air to drift it. A subtle helmet-visor frame borders the view and is hidden in photo mode for clean captures.
• Optional suit sounds (key M or the field guide toggle) play a quiet life-support hum, conducted footfalls, landing thumps, and a radio chime on each discovery; the exterior remains silent. All audio is synthesized in the browser with Web Audio — there are no audio files.
• G or the field-guide button switches between lunar gravity (1.62 m/s²) and Earth gravity (9.8 m/s²) with the same takeoff velocity, so visitors can feel the difference in jump height. The telemetry panel and dust both follow the active gravity.

Boulders, scattered rocks, gravel, and the lunar module use GLB models from the NASA 3D Resources repository (models/); if a model fails to load, the page falls back to procedurally generated geometry. The landscape and remaining materials are generated in the browser. Distant mountains have separate multi-scale rock shading and surface-normal detail, with fine detail faded at small screen sizes to limit shimmer. Regolith piles in soft fillets around rock bases, the ground carries small impact pits and sparse glass-bead-like glints (Apollo crews described the soil sparkling), and large boulders sit in shallow debris aprons. A faint additive glow band hugs the horizon toward the Sun (the levitating-dust horizon glow Apollo crews reported), boot prints are drawn with high-contrast tread, and Earth carries a gentle emissive boost so it reads as the brilliant object it is from the surface. Earth uses the existing Solar System Scope imagery (CC BY 4.0). Earth's apparent size and location are composed for the scene rather than calculated from an ephemeris. The experience intentionally has no wind audio.

Jump gravity is a constant 1.62 m/s², following NASA's average lunar surface value (https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/moon/). Scene distances use metres. The chosen takeoff velocity of 1.8 m/s gives a rise of 1 metre and approximately 2.22 seconds aloft on level ground. Eye height is 1.68 m; walking and brisk walking are 1.55 m/s and 2.8 m/s. Takeoff strength, horizontal acceleration, gait animation, and landing dip are experience settings, not measurements of an astronaut in a specific spacesuit. Rocks currently use conservative horizontal collision bounds, so jumping onto or over large rocks is not supported.

Implementation: moon.html and moon.css provide the expedition interface, moon.js handles rendering and interaction, and lunar-terrain.js exposes deterministic terrain sampling and collision-aware movement through LunarTerrain. The terrain sampler uses the same triangle interpolation as the rendered ground. createWalker(surface, position) returns a grounded locomotion state; updateWalker(surface, state, input, dt, obstacles) updates and returns that state, integrating gravity in steps no longer than 1/120 second. dt is in seconds; movement input contains forward, right, yaw (radians), fast, and a one-shot jump request. A hidden browser tab, the field guide, and photo mode pause the simulation.

lunar-expedition.js contains the discovery positions, lightweight route graph, proximity checks, and validated journal parsing. moon-discoveries.js connects the route to the interface, progress storage, and the on-demand rock viewer. Random large rocks leave a clear corridor around the authored route; the original featured boulders remain. Both the discovery dialog and field guide pause walking and jumping.

NASA 3D Resources models (models/*.glb) are Draco-compressed — every page that loads a GLB also loads DRACOLoader.js and points it at the r128 examples/js/libs/draco/gltf/ decoder path, otherwise the geometry fails to decode and the loader silently falls back.

Mars expedition

The public page is https://www.3dsolarsystem.net/mars-expedition.html (the name avoids colliding with the existing mars.html orbital detail page). It is listed in sitemap.xml, linked from the homepage and generated planet pages, and carries the same indexable metadata as the Moon expedition.

• The same first-person engine as the Moon expedition, retuned for Mars: gravity is 3.71 m/s² (G toggles Earth's 9.8 m/s²), so the same 1.8 m/s takeoff gives roughly a 0.44-metre hop — visibly heavier than the Moon.
• The environment differs deliberately: a butterscotch sky dome, tan dust haze (distance fog), a smaller Sun with a faint blue-tinged halo, thin cirrus-like ice clouds, and two dim moonlets instead of Earth. Terrain includes a layered flat-topped mesa, a wind-rippled dune field, degraded craters, dark dust-devil tracks crossing the plain, ventifact-style elongated rocks aligned to the prevailing wind, and boulders whose tops carry a lighter dust coating — all informed by rover imagery. A live dust devil (a translucent twin-column mesh with scrolling streak texture) wanders the plain, and twin rover-track grooves darken the ground near the arrival point.
• Audio differs too: Mars has a real but thin atmosphere — Perseverance's microphones showed a deep silence broken by occasional faint gusts, so the soundscape is suit-internal sounds plus rare low-frequency gusts, not a constant wind bed. A quiet life-support hum is present on both worlds (Apollo crews heard their suit fans). Footfalls are crunchier than on the Moon.
• Five discoveries — layered mesa, basalt boulder (3D specimen viewer), dune field, a parked Mars rover, degraded crater rim. The rover and crater are on foot only. Progress saves under mzu-mars-discoveries-v1.
• Files mirror the lunar set: mars-expedition.html, mars.js, mars-terrain.js, mars-expedition.js, mars-audio.js. moon-discoveries.js and moon.css are shared — the discoveries module accepts optional expedition, terrain, and strings parameters.

Venus expedition

The public page is https://www.3dsolarsystem.net/venus-expedition.html (the name avoids colliding with the existing venus.html orbital detail page). It is listed in sitemap.xml, linked from the homepage and generated planet pages, and carries the same indexable metadata as the other expeditions.

• The same first-person engine, retuned for Venus: gravity is 8.87 m/s² (G toggles Earth's 9.8 m/s²) — about 91% of Earth, so the same 1.8 m/s takeoff as the Moon and Mars expeditions gives roughly a 0.18-metre hop versus 0.17 on Earth. The near-identical jump is itself a discovery.
• The environment differs deliberately: Venus has no visible sky — thick sulfuric-acid clouds admit only a dim, directionless amber glow where the Sun stands. The cloud deck is procedural horizontal banding drawn on the sky dome (no floating sprite patches); distance fog is dense and orange so far terrain dissolves into haze silhouettes rather than clipping away. The far terrain shimmers subtly (heat-haze vertex wobble) and the cloud deck brightens briefly on each thunder event through a flashBoost sky uniform. Terrain is volcanic, not cratered: fractured basalt slabs, a lava channel, a pancake dome, and ridged tessera-like highlands, inspired by Venera surface photos and Magellan radar maps.
• Rocks are flat fractured plates (as in Venera panoramas), not rounded boulders, and come in mixed sizes — from hand-sized shards to multi-metre embedded plates. Low plates are walkable — the walker steps or jumps onto them and stands on their tilted top planes; tall upheaved slabs and leaning plate pairs still block movement. The lava channel carries a faint pulsing emissive seam, and the ground darkens around it like fresh flow deposits.
• Audio differs too: a 92-atmosphere CO₂ sky carries sound far better than Mars — a low continuous rumble, slow heavy wind-pressure swells, and rare muffled thunder. Thunder events drive a brief lightning brightening of the cloud deck through an onThunder hook.
• The sky has no moons and no other bodies — Venus has no moons and the overcast hides everything. Only the Sun's brighter patch of haze is clickable; it links back to index.html?focus=Sun.
• Five discoveries — basalt slab field, Venera-13-inspired lander, lava channel, pancake dome, tessera highland. The pancake dome and tessera highland are on foot only. Progress saves under mzu-venus-discoveries-v1.
• Files mirror the other expeditions: venus-expedition.html, venus.js, venus-terrain.js, venus-expedition.js, venus-audio.js. moon-discoveries.js and moon.css remain shared.

Mercury expedition

The public page is https://www.3dsolarsystem.net/mercury-expedition.html (the name avoids colliding with the existing mercury.html orbital detail page). It is listed in sitemap.xml, linked from the homepage and generated planet pages, and carries the same indexable metadata as the other expeditions.

• The same first-person engine, retuned for Mercury: gravity is 3.7 m/s² (G toggles Earth's 9.8 m/s²) — nearly identical to Mars on a much smaller world, because Mercury is mostly a giant iron core. The same 1.8 m/s takeoff gives roughly a 0.44-metre hop.
• The sky is the opposite of Venus: no atmosphere at all, so it stays black at noon with visible stars. The Sun looks two to three times wider than from Earth — a hard white disc with a glare halo. Earth and Venus hang nearby as bright points. All three bodies are clickable and link back to the orbital explorer (?focus=Sun|Earth|Venus). There are no clouds, no haze, no wind, and no dust devils.
• Terrain is cratered like the Moon but warmer gray-brown: a large central-peak crater (the rim viewpoint is a discovery), a lobate scarp — a long thrust-fault ridge from Mercury's global contraction, walkable to its crest — and a field of bright-rimmed hollows (a Mercury-exclusive terrain type). A real MESSENGER spacecraft model (NASA 3D Resources) stands in as the relay satellite honouring Mariner 10, MESSENGER, and BepiColombo; no real lander has ever touched Mercury.
• Audio matches the Moon's near-vacuum design: suit-internal fan hum, conducted footfalls, and a radio chime — no environmental sound at all.
• Five discoveries — central-peak crater, ejecta block (rotatable specimen), relay beacon, hollows field, lobate scarp. The hollows field and scarp are on foot only. Progress saves under mzu-mercury-discoveries-v1.
• Files mirror the other expeditions: mercury-expedition.html, mercury.js, mercury-terrain.js, mercury-expedition.js, mercury-audio.js. moon-discoveries.js and moon.css remain shared.

Jupiter descent

The public page is https://www.3dsolarsystem.net/jupiter-expedition.html (the name avoids colliding with the existing jupiter.html orbital detail page). It is listed in sitemap.xml, linked from the homepage and generated planet pages, and carries the same indexable metadata as the other expeditions.

• Jupiter has no surface, so this expedition replaces walking with atmospheric descent: the visitor rides a probe that sinks continuously at a terminal-velocity drift (SINK_SPEED scaled by gravity). Holding Space fires an ascent thruster (THRUST_SPEED); WASD/arrows drift horizontally; there is no jumping and no ground.
• jupiter-atmosphere.js exposes JupiterAtmo — the same createSurface/sampleSurface/createWalker/updateWalker contract as the terrain modules, but walker.y is a free altitude clamped between MIN_ALTITUDE (−360) and MAX_ALTITUDE (420), and walker.grounded stays true so the shared discovery module works unchanged. Gravity is 24.79 m/s² (G toggles Earth's 9.8 m/s², scaling the sink rate).
• The "terrain" is a displaced cloud deck: billowing ammonia tops plus a great-storm vortex (bowl + raised rim) at storm.x/z, topped by a slowly rotating spiral-textured disc for the storm's churn. Vertex colours paint horizontal bands and a rust-red collar around the vortex; the ground shader adds billow shading, wind streaks, and crest brightening, plus a uTime vertex wobble so the deck visibly churns. Roughly 190 soft additive cloud-puff sprites fill the descent corridor (three altitude layers) so the probe flies through haze rather than over a flat plane; a slight emissive lift keeps the deck reading as sunlit cloud, not rock. Sky is a procedural banded dome (fbm turbulence + filament streaks) with a Sun about five times smaller than from Earth; small translucent drifting ice crystals replace rocks (one is the specimen-viewer target).
• Depth drives atmosphere: a darkening uniform dims the banded sky as the probe sinks, fog thickens and shifts toward deep brown, sunlight and ambient fade, and random lightning events fire both a flash uniform and brief additive lightning-bolt sprites below the deck, paired with thunder audio.
• All five expeditions share the post-processing pipeline introduced here: each page loads the r128 examples/js postprocessing modules (unpkg) and renders through EffectComposer — RenderPass → UnrealBloomPass (per-planet strength/threshold: Moon 0.6/0.8, Mars 0.45/0.8, Venus 0.5/0.75, Mercury 0.65/0.72, Jupiter 0.5/0.74) → GammaCorrectionShader → FXAAShader → a custom cinematic pass (vignette + animated film grain). Composer use is skipped on low quality or when the CDN modules fail, falling back to direct rendering.
• No lens flare anywhere. The screen-space lens-flare module (flare-pass.js) was removed: its halo rings and ghost chains read as pasted stickers. Suns are bright basic spheres that the existing bloom pass softens. Atmospheric glows that model real light scattering (the Moon's horizon band, Mars's blue halo) are kept.

Saturn ring-plane cruise

The public page is https://www.3dsolarsystem.net/saturn-expedition.html (the name avoids colliding with the existing saturn.html orbital detail page). It is listed in sitemap.xml, linked from the homepage and generated planet pages, and carries the same indexable metadata as the other expeditions.

• Saturn's rings have no surface to walk or sink through, so this expedition uses ring-plane cruise: the probe drifts forward on its own (CRUISE_SPEED), WASD/arrows add lateral drift and speed (Shift faster), Space rises and C sinks below the sheet. There is no gravity descent — instead the ring plane exerts a gentle tidal pull toward y = 0, scaled by the G gravity toggle (Saturn 10.44 m/s² vs Earth 9.8 m/s²).
• saturn-rings.js exposes SaturnRings — the same sampleSurface/createWalker/updateWalker contract (sampleSurface returns 0 — the "surface" is the ring plane), plus ringDensity(x, z) which both drives the banded sheet texture and gates how densely the instanced ice field populates each band. Altitude is clamped between MIN_ALTITUDE (−140) and MAX_ALTITUDE (300).
• The ring sheet is a pair of translucent 6 km planes (a second offset copy fakes thickness at grazing angles) textured with a band map generated from ringDensity. Density now comes from real data: ringDensity reads a 128-sample table (RING_PROFILE in saturn-rings.js) taken from the alpha channel of textures/2k_saturn_ring_alpha.png (NASA/Cassini-based). The image's x-axis is mapped linearly to planet radii using two anchors checked against the image itself: the Cassini Division minimum (x≈1445) sits at 1.99 R, and the outer A-ring edge (x≈1947) at 2.27 R. Result: the bright B ring (1.53–1.95 R), the dark Cassini gap at ~1.99 R, the dim C ring and the Encke gap all land where they should. Fine ringlet noise is still layered on top. Geometry uses Saturn's true ring radii: the probe cruises inside the Cassini division at ~1.99 Saturn radii, so SATURN_RADIUS = RING_R0 / 1.99. The globe therefore fills ~60° of sky, and the dense B ring between the probe and the planet correctly hides Saturn's lower half. The far ring disc around the globe samples the same ringDensity profile (not a separate texture) and cross-fades with the local sheet between 2.3 and 2.9 km from the start point, so near and far rings are one continuous system. The globe is Lambert-lit and receives the rings' shadow on its southern hemisphere.
• Two instanced ice fields surround the probe: metre-scale tumbling boulders (three geometry variants, placement weighted by band density) recycled in a wrap-around volume as the probe moves, and thousands of additive "snow" specks. A shepherd moonlet (irregular icy body) and a rotating propeller swirl sprite sit in the sheet as discoveries. NASA's real Cassini model (models/cassini.glb, Draco-compressed) holds formation off the port bow as a wingman; the probe hull under the camera is simple geometry.

Uranus sideways ring flight

The public page is https://www.3dsolarsystem.net/uranus-expedition.html (the name avoids colliding with the existing uranus.html orbital detail page). It is listed in sitemap.xml, linked from the homepage and generated planet pages, and carries the same indexable metadata as the other expeditions.

• Uranus reuses the Saturn ring-flight engine with a different character: the probe cruises forward on its own (CRUISE_SPEED), WASD/arrows drift and change speed (Shift faster), Space rises and C sinks below the sheet. The ring plane exerts a gentle tidal pull toward y = 0, scaled by the G gravity toggle — Uranus's 8.87 m/s² is nearly identical to Earth's 9.8 m/s², and that near-match is itself the point of the toggle.
• uranus-rings.js exposes UranusRings — the same sampleSurface/createWalker/updateWalker contract. ringDensity(x, z) returns low densities for thirteen narrow charcoal-dark bands (ε/δ/γ/η/β and friends) instead of Saturn's broad bright sheet; it both drives the sparse band texture and gates how thinly the instanced particle field populates each band. Altitude is clamped between MIN_ALTITUDE (−140) and MAX_ALTITUDE (300).
• The ring sheet is a translucent plane textured with thin dark band streaks; the instanced particle field uses nearly black rock material (0x424c52), so the lumps read as charcoal debris rather than Saturn's glittering ice. A shepherd moonlet (irregular body riding a ring edge) and a small tilt marker — a turquoise globe tipped 98° with a vertical ring of its own — sit in the sheet as discoveries.
• The Sun hangs almost directly over the tipped giant's pole instead of low on the horizon, so light pours down nearly perpendicular to the ring plane. The featureless turquoise Uranus globe (real 2k_uranus.jpg texture, deliberately near-featureless as Voyager 2 saw it) hangs half-submerged on the plane with its narrow rings edge-on. NASA's real Voyager 2 model (models/voyager.glb, Draco-compressed) — the only spacecraft ever to visit Uranus — holds formation off the port bow.
• Post chain mirrors Saturn (bloom → gamma → FXAA → vignette+grain, plus the radial sun-shaft pass). Audio (uranus-audio.js) is the same quiet cabin hum and radio hiss with rarer icePing() ticks, matching the sparser bands.
• Five discoveries pair with the three stations (vista, ring-charcoal specimen, the dark gap, shepherd moonlet, the 98° tilt marker); progress saves under mzu-uranus-rings-v1.
• Files mirror the other expeditions: uranus-expedition.html, uranus.js, uranus-rings.js, uranus-expedition.js, uranus-audio.js. moon-discoveries.js and moon.css remain shared.

Neptune storm-layer flight

The public page is https://www.3dsolarsystem.net/neptune-expedition.html (the name avoids colliding with the existing neptune.html orbital detail page). It is listed in sitemap.xml, linked from the homepage and generated planet pages, and carries the same indexable metadata as the other expeditions.

• Neptune reuses the cruise engine but moves it inside an atmosphere: instead of a ring plane there is a deep-blue cirrus deck (y = 0) whose streak lanes spiral around a Great Dark Spot vortex at (VORTEX_X, VORTEX_Z) — stormDensity(x, z) returns higher density along winding spiral arms and near zero inside the dark eye. The probe cruises forward on its own; WASD/arrows drift, Shift is faster, Space rises to MAX_ALTITUDE (300), C sinks to MIN_ALTITUDE (−140) where the haze thickens. Pressing G compares Earth's 9.8 m/s² with Neptune's 11.15 m/s².
• neptune-storm.js exposes NeptuneStorm — the same sampleSurface/createWalker/updateWalker contract as the ring modules, plus VORTEX_R so the painted vortex disc and the density eye share one radius.
• The deck is two translucent canvas-textured sheets streaked tangentially around the vortex; an instanced field of pale methane-ice crystals recycles around the probe; the vortex disc (radius VORTEX_R, spiral-streak texture) turns slowly on the deck; a white Scooter-style racing cloud and a small spinning-disc marker sit as discoveries. Triton hangs in the haze as a clickable sky body alongside the Sun and Earth. NASA's real Voyager 2 model (models/voyager.glb) — the only spacecraft ever to visit Neptune — holds formation off the port bow, the same ship as Uranus's flyby.
• Post chain mirrors Uranus (bloom → gamma → FXAA → vignette+grain, plus the radial sun-shaft pass). Audio (neptune-audio.js) adds a restless wind howl under the cabin hum, with icePing() ticks gating on stormDensity inside the lanes.
• Five discoveries pair with the three stations (storm vista, cirrus crystal specimen, the storm wall, the shear line, the vortex spinner); progress saves under mzu-neptune-storm-v1.
• Files mirror the other expeditions: neptune-expedition.html, neptune.js, neptune-storm.js, neptune-expedition.js, neptune-audio.js. moon-discoveries.js and moon.css remain shared.

All eight expedition field guides open with a "What you are seeing" feature list — a localized card list (planet-facts markup, feature-list element, per-page features dictionary entries rendered by applyLanguage) that names each visible landmark and ties it to the real observation it is based on, so visitors can read the planet's signature features without walking.

After changes, run:

node generate_seo_pages.cjs
node validate_site.cjs
node --check moon.js
node --check lunar-terrain.js
node --check lunar-expedition.js
node --check lunar-audio.js
node --check moon-discoveries.js
node --check mars.js
node --check mars-terrain.js
node --check mars-expedition.js
node --check mars-audio.js
node --check venus.js
node --check venus-terrain.js
node --check venus-expedition.js
node --check venus-audio.js
node --check mercury.js
node --check mercury-terrain.js
node --check mercury-expedition.js
node --check mercury-audio.js
node --check jupiter.js
node --check jupiter-atmosphere.js
node --check jupiter-expedition.js
node --check jupiter-audio.js
node --check saturn.js
node --check saturn-rings.js
node --check saturn-expedition.js
node --check saturn-audio.js
node --check uranus.js
node --check uranus-rings.js
node --check uranus-expedition.js
node --check uranus-audio.js
node --check neptune.js
node --check neptune-storm.js
node --check neptune-expedition.js
node --check neptune-audio.js

Route verification includes both directions of every route segment at all three terrain detail levels, distant/airborne discovery rejection, duplicate prevention, and invalid saved-data handling. Browser checks should cover walking the complete route with scene obstacles, specimen rotation/zoom, quick-travel without automatic progress, refresh persistence, storage-disabled fallback, and touch discovery controls.

The validator also checks lunar terrain determinism, crater height, triangle interpolation, rock collisions, slope limits, region boundaries, jump trajectories at different frame rates, prevention of double jumps, landing, walking acceleration/stopping, and airborne momentum. Browser-script policies are evaluated in an isolated Node VM so validation does not depend on an enclosing directory's CommonJS/ES-module settings. For browser checks, exercise desktop walking/dragging, Space jump and landing, touch movement/jump, all five stops, English default in a Chinese browser, camera-motion, gravity and sound switches, photo download, and the round trip to the orbital explorer. This remains a visual prototype; more detailed suit animation and device-specific performance tuning remain future work. If a local preview shows an older interface after changes, perform a hard refresh (Ctrl+F5).

License status

No project-wide open-source license is included. Unless the repository owner publishes a license, no permission to copy, modify, or redistribute the project is granted beyond rights provided by law. Third-party assets remain subject to their own terms.

Realism pass: Mars, Moon, Venus, Mercury and distant suns

Checked each expedition's first-glance scene against known physics and removed painted or sticker-like effects.

• Stars: Moon, Mars and Mercury now have real star fields. Stars are fixed-pixel points so distant ones stay visible. Mars's stars are hidden in daylight (dusty air) and appear under the new Night sky / 夜空 button, which also dims the sun, cools the fill light and darkens the sky.
• Mars rocks: boulders are reddish basalt under red-brown dust. The horizontal stripe banding in the ground shader was removed because real terrain does not band like that.
• Venus: the sun behind the clouds is now a native Three.js sphere with view-angle falloff instead of a canvas sprite. Boulders use the real Bennu/Itokawa models (procedural rocks remain a fallback). Lighting is mostly sky light with a weaker direct sun, so shadows are faint, as they are under Venus's thick atmosphere.
• Moon: rocks and regolith are neutral grey and lit by a hard-edged sun with no air haze, which matches the physics. No change was needed.
• Mercury: rocks are a touch warmer grey. Mercury's sun radius already matches its real angular size (about 1.4 degrees).
• Distant suns and Earth dots: Mars keeps its true sun size (about 0.35 degrees). Jupiter, Saturn, Uranus and Neptune use a minimum visible size of about 0.2 degrees for the sun and Earth points, because the real discs are 0.02 to 0.1 degrees and would be invisible. Real angular sizes are much smaller; these are visibility-adjusted.

Mars ground from real data; Saturn moons; Jupiter/Neptune vortices

• Walkable Mars ground now uses a real HiRISE DTM. textures/mars_hirise_jezero_2m.bin is a 1 km patch of the HiRISE Jezero DTM (DTEEC_023247_1985_022957_1985_U01, 1 m/px, PDS). build_mars_hirise.cjs reads only the needed rows through HTTP range requests (the full file is 642 MB, not downloaded). The file stores the ground detail (height minus a 50 m average) at 2 m, so the hand-placed mesas, route and stations stay where they are. The whole 300 m walk zone is covered. validate_site.cjs re-checks every Mars route with this detail applied; the steepest walkable slope is about 34 degrees, below the 40 degree block threshold.
• Far Mars horizon uses real MOLA topography. textures/mars_mola_jezero_16ppd.bin (640 x 640, 16 px/deg, 3.7 km/px) comes from the 33 MB NASA MEGDR file via build_mars_dem.cjs. Heights are exaggerated 5x.
• Higher-resolution options checked: HiRISE DTMs are ~0.5-0.6 GB per site; the HRSC/MOLA blend at 200 m is 11 GB (3.55 GB as a cloud-optimised GeoTIFF). The 200 m data would only give about 5 samples across the 600 m walk zone, so HiRISE is the useful step.
• Saturn moons: Enceladus, Tethys, Dione and Iapetus are now in the scene, with their own textures (resized to 2048 x 1024 for deployment; .vercelignore no longer excludes them). Real periods (REAL_PERIODS) and real semi-major axes were added so real-distance mode places and spins them correctly. Titan now sits outside Rhea and the artistic speeds fall with orbital period. Scene orbit radii are artistic, not to scale.
• Jupiter and Neptune: the cloud-puff sprites were removed (the volumetric cloud and storm layers already provide the depth). The Great Red Spot and Neptune's Great Dark Spot are now native shader spirals instead of painted canvas. Jupiter's lightning is a thin jagged line instead of a vertical textured plane.
• Mars sky clouds are now noise-textured shader planes.
• Uranus rings use the published radii and optical depths (Epsilon at the station's 2670 units).
• Not yet verified on screen: Jupiter's lightning (random, not captured), the Great Red Spot close-up, and the Saturn moons in the browser (they load without console errors).

Attribution: Nix texture

• textures/moon_nix_celestia.jpg (2048 x 1024) is the Nix map from the CelestiaContent texture set, which reprojects processed New Horizons images. Author: Askaniy Anpilogov, licence CC-BY-3.0. Source: https://github.com/CelestiaProject/CelestiaContent/blob/master/textures/medres/nix.jpg
• Hydra, Styx and Kerberos have no published surface maps (Hubble cannot resolve them; New Horizons imaged only Nix and Hydra in detail). Hydra and Nix shape models exist (Porter, figshare) but carry no colour data, and Hydra's colour map was not found in the Celestia set. Those three keep the procedural cratered surface.
• models/hydra_shape.json is Hydra's shape model from Porter et al., figshare 12779975, licence CC BY 4.0 (https://figshare.com/articles/online_resource/Shape_Model_of_Hydra/12779975). It was decimated from 52,488 to 1,066 triangles by build_hydra_shape.cjs. It has no colour data, so Hydra keeps the procedural tint.
• models/nix_shape.json is Nix's shape model from Porter et al., figshare 12779948, licence CC BY 4.0 (https://figshare.com/articles/online_resource/Shape_Model_of_Nix/12779948). Decimated from 80,000 to 4,052 triangles by build_hydra_shape.cjs <stl> nix. Nix uses its Celestia map on this shape.
• Hi'iaka is drawn as a triaxial ellipsoid with axes 240 x 180 x 143 km (Ortiz et al., stellar occultations, 2025, Nature Communications; https://www.nature.com/articles/s41467-025-65749-1). Its colour follows the reported visible albedo of 0.76. Namaka has no measured shape or map; it stays a sphere with its designed colour.
• Untextured moons (Hiaka, Namaka, Styx, Kerberos, Hydra) now use their designed colour instead of the default white.

Photo-scanned ground, rocks and bootprints (walking expeditions)

• Ground: expedition-ground.js puts a photo-scanned soil material on the Moon, Mars, Venus and Mercury ground (colour, normal and roughness maps). Source: ambientCG "Ground054", CC0. The colour map is desaturated (textures/regolith_*.jpg, about 720 KB total) and each world tints it.
• Rocks: boulders use Poly Haven's photo-scanned "Moon Rock 01" and "Moon Rock 03" models (CC0, models/rocks/, about 2.7 MB with textures) instead of the Bennu/Itokawa asteroid models. Venus now uses the scanned material too, which fixed its rocks rendering black.
• Bootprints: the footprint decal is the real Apollo 11 bootprint photo (NASA AS11-40-5878, public domain), cleaned of reseau crosses, rotated upright and given a soft alpha edge (textures/footprint_apollo.png, 43 KB). Each world tints it.
• Saturn and Uranus: the remaining cloud-puff sprites were removed, matching Jupiter and Neptune.
• Not done: the Venus science station is still built from primitives. A free Venera 12-14 lander model exists on Sketchfab (tashtego), but it needs a manual, logged-in download.

Real star sky and generated Milky Way (home page, Moon, Mercury)

sky-galaxy.js (SkyGalaxy.create(options)) replaces the old Milky Way photo (2k_stars_milky_way.jpg, no longer loaded), the random starfield and the canvas "nebula" sphere.

• Bright stars are real. textures/bsc5_stars.bin (73 KB) holds all 9,096 stars of the Yale Bright Star Catalogue (BSC5, public domain, http://tdc-www.harvard.edu/catalogs/bsc5.html): J2000 position, magnitude and a colour temperature from the spectral type. Rebuild with node build_star_catalog.cjs <BSC5 file>. Constellations appear in their true places; size and brightness follow magnitude.
• Scene frame. XZ is the ecliptic plane, +Y the ecliptic north pole, ecliptic longitude 0 along +X (the same direction the planets orbit in main.js). Checked: Deneb comes out at l = 84.3°, b = +2.0°; Sirius at l = 227.2°, b = -8.9°; Antares at l = 351.9°, b = +15.1°.
• Milky Way band. A shader works in true galactic coordinates: thin disc, thick disc and a yellowish bulge, plus named features at their real positions — Scutum, Sagittarius and Cygnus star clouds, the Great Rift, Coalsack, Pipe and Rho Ophiuchi dark clouds, red emission nebulae (Carina, Lagoon, North America, Orion, Barnard's Loop), the Magellanic Clouds and M31. A soft exposure curve stops it clipping and dithering removes banding. Fainter stars (tens of thousands, below naked-eye limit) are spread with the same density model.
• Performance. When a renderer is passed, the band is rendered once at start-up into a half-float cube map (2048 px per face; 1536 on Balanced, 1024 on Low) and each frame only samples it. It is still generated in code, not an image file.
• Expeditions. Moon and Mercury use centerToward to turn the galactic centre to the upper right of the starting view, away from the Sun. Mercury's separate black sky sphere was removed; the band now shows there.
• Limits. The band is a model, not a survey map: the dust lanes and star clouds follow published positions, but their fine shapes come from noise.