1. In Blender, go to Edit > Preferences > Add-ons > Install and pick the Nimbus .zip. The file is around 300 MB because the cloud shape library is included.
2. Tick the checkbox to enable the addon.
3. In the 3D Viewport, press N. You will see a Nimbus tab on the right.

1. Open the Nimbus tab and click the Clouds sub-tab.
2. Press Build Sky. Nimbus creates the atmosphere, a sun, a moon, a camera, and three cloud layers using the included shape library. The status line will say "Simulated clouds loaded."
3. Press F12 to render. The default result is a clear day with a mixed cloud deck.

The layer list works like layers in Photoshop. Each row is its own cloud deck with its own type, altitude and settings. The default stack is Low (stratocumulus), Medium (cumulus) and High (congestus). Add, remove or hide layers as you like, then press Build Sky to apply.

Nimbus comes with 5 cloud shapes grown by real smoke simulations. Each cloud type reshapes that same library its own way: cumulus uses them as baked, stratocumulus flattens them into wide patches, congestus stretches them into towers. That is why the clouds do not look procedural. You never have to bake anything. If you want your own unique shapes: change the seed, press Bake Hero Clouds, and let it run in the background. It takes about 25 minutes per shape and uses a lot of CPU and RAM, so avoid rendering while it runs. When the status line says the bake is done, press Load Hero Clouds. Your own bakes are used instead of the included shapes automatically.

Export Cloud VDB saves the cloud shapes as OpenVDB files (the grid is named density_noise) so you can use them in Houdini, Unreal, or any other software.

Real volumetric clouds are too heavy to show in the viewport all the time, so Nimbus shows light placeholder clouds instead. They sit exactly where the real clouds will be, across the full 50 km sky, and they update live while you drag the sliders. No rebuild needed:

• Amount adds or removes placeholders. Size and Depth reshape them. Altitude and the offsets move the deck. Seed shuffles the layout. Density makes their color more solid or more faint.
• Placeholders never show up in renders.
• If you want to see the real clouds while working, turn on True Clouds in Viewport and switch to rendered shading. This is heavy, so expect a wait on big scenes.

Each layer row also has four small buttons for exactly how that layer shows up: Preview (placeholder in the viewport, real clouds in renders — the fast default), Viewport (real clouds shown live, heavier), Render Only (nothing in the viewport, still renders), and Hidden (the layer is fully off). Mix and match per layer instead of using the global toggle for everything.

• Preview renders: 1152x470 at 32 to 48 samples takes about 5 to 10 minutes on an RTX 4060.
• Final renders: 1080p at 64 or more samples takes about 15 to 25 minutes. The denoiser handles volumes well, so more samples are usually wasted.
• The first build after opening a file takes a few extra seconds while the shape library loads.
• 8 GB of VRAM handles full scenes. Distant clouds are automatically kept cheap.