Press one button. Your world background is a nebula, and it is lighting your scene. About three seconds at Preview quality, in EEVEE and in Cycles.

A free HDRI is one sky. This is a generator: change the seed and you have another nebula that nobody else has, up to 4096×2048, tuned by sliders rather than picked from a list. It bakes to an ordinary Environment Texture, so once it exists it costs the renderer nothing — unlike a volumetric nebula, which you pay for on every frame.

Light Boost — the slider that makes this usable

A real nebula is dim: linear radiance around 0.01–0.2. So a sky that looks correct behind the camera leaves your models nearly black. That is astronomy, not a bug, and it is why most space backdrops end up as wallpaper instead of as light.

Nebula Forge splits the World on Light Path > Is Camera Ray. Camera rays see the sky at strength 1, so the backdrop stays photometrically correct; every other ray sees it multiplied by Light Boost. Backdrop and key light on separate sliders, live, with no re-bake. Taking the boost from 6 to 40 changes the light on a diffuse reference ball by 6.7× in Cycles (exactly 40/6, linear) and 4.3× in EEVEE, and leaves the backdrop pixel-identical in both — measured on Blender 5.2.

The colour is derived, not painted

Star colour comes from Planck’s blackbody law at real stellar temperatures. The gas emits in the actual nebular lines — Hα, O III, Hβ at the Balmer decrement. Dust follows Beer–Lambert extinction, so dark lanes redden what is behind them. Ionisation runs outward to a Strömgren radius, which is why O III teal sits inside and Hα red outside.

One honest note, because this audience will check: on the two narrowband presets the colours follow the standard SHO/HOO false-colour conventions rather than mapping wavelengths directly. Three of the five presets map an actual spectrum; two map a convention.

What you get

• Five presets: Orion Bloom, Pillars (Hubble SHO), Dark Rift, Ion Storm, Deep Field
• Seed-driven, so each preset is an unlimited family rather than one picture
• Quality from Preview (~3 s) to Ultra (4096×2048)
• Sky Rotation and Light Boost re-apply instantly, with no re-bake
• Save Sky — export the equirectangular sky as EXR (full linear range) or PNG
• Save Volume — export the source volume as OpenVDB, imported into the scene with its emission material already wired (a bare .vdb renders black without it)

Not generative AI

No image model is involved at any point. It is a procedural raymarcher: deterministic maths, reproducible from a seed, and the seed ships with every result.

Requirements

Blender 3.6 or newer — tested on 5.2 LTS. Python and numpy only: no external dependencies, no downloads, no account.