A screenshot of a blender window being used for painting out puppeteer's arms from some raw video footage. At the top is a compositing node setup which is using an animated mask to replace areas of the video with a clean plate image. Below are two viewers. On the right is the mask editor where you can see mask shapes drawn around the puppeteer and the puppet's body where they overlap. On the left is the final composite with the puppeteer magically disappearing!