AlphaBender v1.1

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Contributor: Fynn Laue
Fast & precise eroding of alpha channel
13.1, 12.2, 12.1, 12.0, 11.3, 11.2, 11.1, 11.0, 10 or later
Linux, Mac, Windows
11 Sep 2021

Change log


  • Fixed a bug that caused the alpha to change wrongly when weight < 0 even if hardness = 0
  • Improved accuracy especially when dealing with large, blurry areas


Modifying alpha channels is probably one of the things I do most when compositing. I've found Nuke's Erode and Dialate nodes to be a bit too limiting and slow for many of these operations. So I made this lightweight tool for growing and shrinking the alpha channel. It works well for both small adjustments, like 'leaning' the center of a gradient slightly towards one side, and big modifications.

Also useful for things such as:

  • Despotting a key
  • Smoothing out jagged edges
  • Making big mask expansions/contractions

How to use

First you 'prep' the alpha channel to only show what you want to use as a base:

alphaBender demo02 v004

Then you 'bend' the result of prep to grow or shrink and add some blur if needed:


Modifying a simple linear ramp illustrates how the hardness and weight knobs affect gradients:

alphaBender demo03 v004


Inner workings

Runs on Blur and Grade nodes so it's simple and fast

alphaBender v1.0 nodegraph

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