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Mask Apply

Node icon
Mask

Applies a mask as the alpha channel of an image. This is the standard way to cut out, reveal, or restrict image areas.

The Mask Apply node uses a mask to control where an image is revealed.
Three panels: the original image, the mask, and the image after the mask is applied.

Mask Apply turns a mask into real transparency. In the default Cut Out mode the mask replaces the image’s alpha: white stays visible, black becomes transparent. Intersect multiplies the image’s existing alpha by the mask, so soft edges blend smoothly where both carry meaningful alpha.

Mask Fit decides how a mask of a different size is mapped onto the image: None (the default) refuses a mask of another size, and Stretch, Fit, and Fill resize the mask to the image.

When the mask covers nothing, the node says so (The mask covers nothing, so the result is fully transparent.).

Texture sets

Section titled “Texture sets”

Mask Apply takes a texture set or a whole library on its image input and edits the set’s Opacity, its one cutout: Cut Out replaces the Opacity with the mask, Intersect multiplies it. Every map passes through untouched. One mask over a library fits each set by Mask Fit, so one node overrides the Opacity of every trim. To lay a masked material over another, follow Mask Apply with a Merge Over. The mask input takes a mask, not a set; use Split Texture to take a map out of a set as a mask.

Parameters

Section titled “Parameters”

Pins

ImageImage
InputRequired
MaskMask
InputRequired
ImagePixels or Texture
Output

Mask

ModeChoice
Default: Cut Out

How the mask is applied to the image alpha channel

  • Cut OutReplace the image's alpha with the mask: white areas visible, black areas transparent.
  • IntersectKeep only pixels where both the image and mask are opaque.
Mask FromChoice
Default: Luminance
Color image connected to the mask input

How the connected color image is read as a mask

  • LuminanceRead the image's brightness as the mask. The default.
  • AlphaRead the image's transparency as the mask.
  • RedUse the red channel as the mask.
  • GreenUse the green channel as the mask.
  • BlueUse the blue channel as the mask.
Mask FitChoice
Default: None (native size)
Mask connected

How the mask is sized when it doesn't match the image

  • None (native size)Center the mask at its native size, with no resizing. Unmasked regions are unaffected.
  • StretchStretch the mask to exactly match the image dimensions. May distort the mask shape.
  • Fit (letterbox)Scale the mask to fit inside the image, preserving aspect ratio. Letterboxes where needed.
  • Fill (crop)Scale the mask to fill the image, preserving aspect ratio. Crops edges if aspect ratios differ.

Usage Tips

Section titled “Usage Tips”
  • With Mask Fit on None the image and mask must be the same size, or the node reports an error naming the fix: set Mask Fit, or put a Resize on one input (over a set, cut the mask with Crop At Its Place).
  • Wire several Mask Apply nodes in series to combine several mask effects.
  • Roto can output the masked image itself in the same modes, with no Mask Apply needed.
Section titled “Related Nodes”