Why Your Procedural Planet's Night Side Is Still Lit — UE5 Terrain, Foliage & Clouds
My procedural UE5 planet looked great — until I flew to the night side and found glowing white clouds, a gold speckle crawling across the dark terrain, and an exposure that washed the whole frame out. This video is the debugging story and the fix: correct day/night lighting on a planet you can see whole from orbit.
A planet breaks the assumptions every local scene relies on — you see the lit and the shadowed hemisphere at the same time. I walk through three separate causes and their fixes:
• Clouds — UE's Volumetric Cloud shares ONE sun-transmittance value across the whole layer, so the night side inherits the lit side's light. Fix: Use Per Sample Atmospheric Light Transmittance.
• Terrain & foliage — a directional light isn't occluded by the planet's own body (cascaded shadow maps can't span a 50 km world), so the sun lights sun-facing slopes and foliage on the night side. Fix: a shader-space day/night terminator — dot(up, sunDirection) from the macro sphere normal, driven by a Material Parameter Collection (PlanetCenter + SunDirection), multiplied into BaseColor AND Specular.
• Exposure — auto-exposure re-brightens the dark hemisphere. Fix: a fixed exposure for the from-space view.
Also covered: why shadows can't fix this, the subtraction-order / PlanetCenter-vs-ObjectPosition gotchas, only updating the parameter collection when values actually change (a static sun writes once), and how it behaves across many planets.
The lesson that generalises: when the engine's occlusion can't reach your scale, answer the lighting question analytically in the material instead of fighting a shadow system.
#UnrealEngine #UE5 #GameDev #IndieDev #ProceduralGeneration #PlanetGeneration #UE5Lighting #VolumetricClouds
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Why Your Procedural Planet's Night Side Is Still Lit — UE5 Terrain, Foliage & Clouds (YouTube)