Volumetric clouds with real structure
Four layer types — a flat stratus deck, fair-weather cumulus, deep rain-bearing nimbostratus, and towering cumulonimbus with anvils — all grown from one shared convection field rather than four separate systems. Storms carry their own lightning, lit from inside the cloud.
Atmosphere derived from physics, not a tint
Rayleigh scattering, Mie haze, an ozone-shaped layered absorber and a uniform gas absorber, each per kilometre. Fourteen presets — Earth-like, Mars, Venus, Titan, the four ice/gas giants, ocean, desert and ice worlds, a thin trace atmosphere, and vacuum — plus full manual override of every coefficient.
Weather that isn't a uniform haze
Coverage is driven by one weather field with cyclones, frontal bands and latitude banding for gas giants, so clear sky and solid overcast both actually occur. Paint coverage by hand on a 2,048×1,024 equirectangular map, or pin a thunderstorm exactly where you want one.
One height field, sphere or plane
The same signed height field answers "how far above the ground, which way is up" for a planet's surface and for a flat map. Orbit and ground level read the same terrain, so nothing changes shape when you fly down to it.
A star with a real black-body colour
Place a Welkin Star, pick a spectral type from O to M (or set temperature, radius and mass directly), and its colour comes out of the temperature — nothing is tinted by hand. Illuminance is physical: about 128,000 lux at one astronomical unit for a Sun-like star, falling off by the inverse square.
Orbits with a real period, not a slider
Any actor can orbit a star or another planet — moons around planets, stations around moons. Periods come from Kepler's third law and the star's mass, not a typed-in number, and position is a closed-form function of time: no integrator, no drift, and scrubbing time backwards works.
The camera rides along near a planet
A body on a short orbit can move tens of thousands of kilometres a second. Close to a planet's surface the camera — and, optionally, nearby ships and stations — take the same step the planet just took, so the ground holds still under your feet instead of sliding out from under the world.
Self-contained, and plays fair with others
Doesn't use the engine's Volumetric Cloud or Sky Atmosphere, and doesn't write to project-wide CVars. Drop it into an empty UE5.5 project and it works; drop it beside a terrain or another atmosphere plugin and it still reads scene depth correctly rather than fighting for the sky.
