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Merge

Merge
Composite

Combines two images with Porter-Duff coverage operators (Over, In, Out, Stencil, Plus, and more), the alpha-driven counterpart to Composite’s color blending.

Merge combines its A (foreground) and B (background) inputs by how their coverage (alpha) interacts, rather than by how their colors blend. Where Composite and Layer answer “how do these colors mix”, Merge answers “which pixels survive, and whose shape wins”. Nine operators cover the classic Porter-Duff set: Over, Under, In, Mask, Out, Stencil, Atop, Xor, and Plus, with Divide and Multiply added for straight arithmetic on color.

That makes Merge the tool for knock-outs, stencils, and silhouette work: punch a logo’s shape out of a texture with Stencil, cut a texture to a character’s silhouette with In, or slide a fill behind existing artwork with Under. Plus is a straight linear add, the correct way to sum premultiplied light passes such as glows or the Relight node’s specular output.

Two more operators, Divide and Multiply, break the coverage rule: they do plain per-channel arithmetic on straight color rather than combining alpha. Reach for them to unpack or repack a render pass, such as dividing a lit render by its albedo to recover the lighting, then multiplying a retouched albedo back in.

The Mix slider dissolves between the untouched B input (0) and the full merge result (1), so you can dial any operator back without touching the A branch.

Parameters

Section titled “Parameters”

Pins

AImage
InputRequired
BImage
InputRequired
ImageImage
Output

Merge

OperationChoice
Default: Over

Composite/Layer = how the colors blend; Merge = how the coverage (alpha) combines.

Divide/Multiply are the exception: plain per-channel arithmetic on straight color, not a coverage combine.

  • OverA over B, the standard composite: A wins where they overlap, B shows through A's transparency.
  • UnderA slips behind B: B keeps priority and A fills only where B is transparent.
  • InKeeps A only where B has coverage, cutting A to B's silhouette. B's own pixels are discarded.
  • MaskKeeps B only where A has coverage: A acts as the cut shape for B.
  • OutKeeps A only where B is empty, punching B's silhouette out of A.
  • StencilKeeps B only where A is empty, punching A's silhouette out of B. The classic knock-out.
  • AtopA shown only where B has coverage, composited over the rest of B: A takes on B's silhouette.
  • XorKeeps both images, but only where they do not overlap.
  • PlusAdds A and B together, a premultiplied linear add for glows, flashes, and summed light passes.
  • DivideDivides A by B channel by channel on straight color, ignoring coverage: pulls one multiplied pass back out of another, such as recovering lighting by dividing a lit render by its albedo.
  • MultiplyMultiplies A and B channel by channel on straight color, ignoring coverage: repacks a light or albedo pass onto its base, the inverse of Divide.
MixNumber
Default: 1.00 Range: 0.00–1.00

Dissolve between the untouched B input (0) and the full merge result (1). Dials any operator back without changing the A branch

Usage Tips

Section titled “Usage Tips”
  • Reach for Merge when you care about shape and coverage; reach for Composite or Layer when you care about color blending.
  • Stencil is the classic knock-out: A’s silhouette is punched out of B.
  • Use In to cut a texture or pattern to the silhouette of another image in one step.
  • Plus expects premultiplied inputs; run straight-alpha sources through Premult first for correct edges.
  • Divide and Multiply ignore alpha and work channel by channel on color: use Divide to pull one multiplied pass back out of another, and Multiply to combine them again.
Section titled “Related Nodes”