Volume Fog Node

Volume Fog computes, for each pixel, the amount of fog crossed between the camera and the visible surface (read from the Position channel). The longer the path through the defined volume, the denser the fog → a realistic atmospheric effect.

Major advantage: you can tune Center, Size, Density and Color in real time without a 3D re-render. Ideal for adding mist in a valley, smoke in a corridor, urban smog, or unifying the atmosphere of mismatched shots.

• Effects Library: Tools > Position > Volume Fog
• Quick add: right-click in the Node Editor → Add Tool > Position > Volume Fog

The node integrates the fog density along the camera → surface ray, using the world Position coordinates. The simplified formula:

Defined volume (Center + Size)

A 3D box centered on Center, with dimensions set by Size. The fog only exists inside this box.

Per-pixel computation

Distance between the camera (ray origin) and the surface (Position read) = ray length. The portion intersecting the fog box → multiplied by Density → the amount of visible fog.

Final composite

The fog is mixed with the original image according to the computed amount and the fog color. The farther the object / the longer the path, the more atmospheric it becomes.

• Image (orange) - the beauty image to add the fog to.
• Position (green) - an image containing the World Position channel (from a 3D EXR or a Position node).
• Effect Mask (blue) - optional.

Valley atmosphere fog:
3D EXR (Beauty + Position) ─┬── Volume Fog
                            │      (Center 0,0,0 / Size 1000,50,1000
                            │       Density 0.3 / Color cool blue)
                            └────── Position
                                      ↓
                                   MediaOut

Fog in a corridor:
3D EXR ─┬── Volume Fog
        │      (Center positioned in corridor
        │       Size narrow elongated)
        └── Position channel
              ↓
            MediaOut

Stacked multi-Volume Fog:
3D EXR → Volume Fog 1 (low ground fog) → Volume Fog 2 (smoke layer)
       → MediaOut

Center X / Y / Z (defaults: 0,0,0)

Center of the fog volume in the 3D scene space. Adjust it to place the fog where you want it (valley, corridor, etc.).

Size X / Y / Z (defaults: 1,1,1)

Dimensions of the fog box. Adapt them to the scale of the scene. For ground fog: small Y, large X and Z. For a column of smoke: large Y, small X/Z.

Density (default: 0.5)

Concentration of the fog. Higher = pixels quickly become opaque as they cross the volume. 0.1-0.3 = subtle, 0.5-0.8 = atmospheric, 1.0+ = dense / almost solid.

Falloff (default: 0.5)

Softening at the edges of the volume. 0 = hard edge, 1 = very soft transition. For natural fog, use 0.5+.

Color (default: white)

Color of the fog. Bluish = a humid / distant atmosphere, yellow-orange = a dusty / sunset atmosphere, neutral gray = generic mist.

Camera Position X / Y / Z

Position of the camera in the 3D scene. It must match the real camera used for the render. Often retrieved through a connected Camera 3D node.

• Large-scale cinema atmosphere - a panoramic view, fog added by depth = a natural "depth haze" effect without re-rendering.
• Ground fog - Volume Fog with a low Y, spread out in X/Z = cinematic ground fog.
• Urban smog - a rendered city, dense Volume Fog added with a yellowish color = air pollution.
• Fog in a corridor / room - a volume placed precisely in the architecture = realistic contained haze.
• Unifying mismatched shots - shots rendered separately with different atmospheres → uniform Volume Fog = visual consistency.
• Underwater effect - very dense Volume Fog + blue-green color = an underwater mood without a fluid render.
• Fast iteration after rendering - adjust the fog density / position in real time without relaunching a Cycles or Arnold render that takes hours.

• Position channel required - without a Position channel as input, the node cannot compute the distances. Connect a multilayer EXR or a Position node upstream.
• Camera Position is critical - a camera mismatch → incorrect fog. Use the exact coordinates of the 3D render camera, or connect a Camera 3D scene manager.
• Stack several Volume Fogs - ground fog + smoke layer + atmospheric haze = a rich multi-layer atmosphere. Each Volume Fog can have a different Center/Size/Color.
• Falloff 0.5+ for realism - below that, transitions are visible at the edges of the fog volume; above it, it looks more organic.
• Modest Density = a pro result - start at 0.1-0.2, then increase gradually. Too dense = mush that eats the image.
• Color matching with the scene lighting - tint the fog with the dominant color of the scene lighting (e.g. golden hour → yellowish fog). It avoids the "pasted on in post" effect.
• Animate Center for moving fog - move the center over time to simulate drifting mist.
• For truly volumetric fog effects (god rays, light shafts), prefer rendering directly in 3D - Fusion's Volume Fog makes uniform fog, not volumetrically lit fog.