↔️
AlphaBender
type
gizmo
tags
nuke
tl;dr
Fast & precise eroding of alpha channel
date
Jul 1, 2021

Change log

 v1.1

  • 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

About

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.
☢️
Available on Nukepedia here
Also useful for things such as:
  • Despotting a key
  • Smoothing out jagged edges
  • Making big mask expansions/contractions
  • Pre-processing alpha for edge extension

How to use

First you "prep" the alpha channel to only show what you want to use as a base
First you "prep" the alpha channel to only show what you want to use as a base
Then you "bend" the result of prep to grow or shrink and add some blur if needed
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
Modifying a simple linear ramp illustrates how the hardness and weight knobs affect gradients

Inner workings

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