Richard Frazer had a look at the Mocha Pro Remove Tool in action, and wondered if he could recreate the underpinnings completely in Nuke. Mocha Pro’s Remove will take a track and a clean plate and automatically fill in the parts, removing unwanted elements from the shot with parts of the clean plate.
add un Unpremultiply, which immediately fills in the transparent areas, and an instant cleanplate (almost).
Richard had a go trying to figure out a technique to do something similar in Nuke, and two minutes later he had a solution that offered the same functionality.
Typically generating a clean plate requires you to stabilize a shot and take some frames from various parts and times in the footage where the areas of the background are clear or revealed. Then you can paint or stitch all those elements together to remove the foreground.
Richard walks through the process of automatically generating a clean plate in Nuke on his blog. He also automated the process into a handy little script that offers a simple UI to complete the task. Check out source code for Auto Clean Plate on Github.
Richard notes that the main downside to this is that it gets very heavy. The optical flow used in the F_VectorGenerator is pretty processor intensive, and then the FrameBlend is asking Nuke to calculate around 150 frames of it at once.