Volume Mask Node

Volume Mask tests, for each pixel, whether its 3D position (read from the Position channel) is inside the defined volume. Output: a white/black matte with optional falloff at the edges.

Typical case: you want to brighten only the left area of a rendered 3D scene, without tracking a 2D mask (complicated if the camera moves). Volume Mask = a matte that follows the 3D area automatically, regardless of camera movement.

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

Volume Fog

Composites visible fog based on how far the volume is crossed. Output = an image with fog added.

Volume Mask

Generates a white/black matte showing whether the pixel is inside the volume. Output = a mask usable as an alpha to drive other operations.

Rule of thumb: you need a visible fog effect → Volume Fog. You need a mask to drive something else → Volume Mask.

• Position (green) - an image containing the World Position channel.
• Effect Mask (blue) - optional.

Local grade on the left area:
3D EXR ─┬── Volume Mask (Center -10,0,0 / Size 5,5,5)
        │      ↓
        │   Color Corrector (mask = Volume Mask output)
        │      ↓
        └── Merge (foreground = corrected)
              → MediaOut

Light effect in a precise area:
3D EXR ─┬── Volume Mask
        │      ↓
        │   Light Wrap / Glow (mask)
        └── Merge → MediaOut

Combining several Volume Masks:
3D EXR → Volume Mask 1 (area A) → Channel Booleans (max)
       → Volume Mask 2 (area B) → ...
       → MediaOut

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

Center of the volume mask in world space. Place it where you want to isolate.

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

Dimensions of the box. Outside = black matte, inside = white matte.

Falloff (default: 0.5)

Softening at the edges. 0 = hard transitions, 1 = very soft transition. For a natural grade without a visible edge, 0.3-0.5.

Invert (default: Off)

Inverts the mask: white outside, black inside. Useful to mask out an area to exclude.

Shape (default: Box)

Shape of the volume. Box = a rectangular box, Sphere = a spherical volume (with a single Size = radius).

• Grading by 3D area - brighten / saturate only the pixels in a precise area of the scene, without tracking a 2D mask.
• Localized light pollution - add an area with a different tint (red, sodium light) in a 3D portion of the scene.
• Isolating objects by world space - two nearly identical objects in different positions: a Volume Mask around one of them tells them apart perfectly.
• Fog limited to a precise box - combine Volume Mask with a 2D fog effect = a homemade equivalent of Volume Fog with more control.
• Masking for relighting - drive a Light Wrap or Glow only on the elements of a specific area.
• Multi-area composite - several Volume Masks combined through Merge / Channel Booleans = complex grading that stays stable when the camera moves.

• Stable when the camera moves - a big advantage over 2D roto: the 3D area stays fixed in world space. The camera can move freely, the mask follows automatically.
• Visualize it through Color Curves - connect the output to a viewer or Saver to see the mask and calibrate Center / Size visually.
• Sphere for a soft, centered mask - more natural than a box for spotlight effects, glows and localized atmosphere.
• Generous falloff for realism - 0.5+ avoids visible edges. Combine it with a light blur on the mask for a perfect blend.
• Combining with Channel Booleans - several Volume Masks → Channel Booleans (Add / Max) = a combined mask. For subtraction (area A without area B), use Subtract.
• Camera Position not required - unlike Volume Fog, the camera is not needed: the mask is purely spatial.
• Can be animated - animate Center / Size for an area that moves through the scene (e.g. a virtual spotlight following a subject).
• For complex shapes (not a box / sphere), combine several Volume Masks or use an Object ID channel as well.