You probably didn’t become a VFX artist because you love rotoscoping.

Frame-by-frame roto is one of the most tedious tasks in compositing—especially when dealing with hair, fast motion, or complex shapes. But what if Nuke could learn how to do it for you?

That’s where CopyCat comes in. With the right setup, you can train your own AI model to generate mattes automatically, saving hours of manual work.

How to Train CopyCat for Rotoscoping

CopyCat works by analyzing a small set of hand-rotoscoped frames and learning to apply that same matte extraction across an entire shot. The key to getting great results? Training it properly. Here’s how:

1. Roto a Few Key Frames

Before CopyCat can generate mattes, it needs training data—clean mattes that show it what to learn.

• Pick 5–10 unique keyframes throughout your shot. Choose frames where the subject’s shape varies the most (e.g., different poses or angles).
• Create precise mattes using Nuke’s standard roto tools. The better these keyframes, the better CopyCat will perform.

Example: If you’re rotoscoping a person running, choose frames where their legs are in different positions.

If you're still learning the basics of Nuke, here's a great intro to Nuke rotoscoping:

2. Set Up and Train CopyCat

Once you have your training frames, it’s time to set up the CopyCat node.

• Add a CopyCat node to your Nuke script.
• Connect your original footage to the Input and your hand-made mattes to the Ground Truth input.

Next, adjust your training settings:

• Start with low iterations (~1000-2000) for quick tests.
• If the results are good, increase iterations.

Click Start Training, and let Nuke process the data. Depending on your settings, training might take a few minutes to an hour.

3. Apply It to the Full Shot Once training is complete and you're happy with the results, it's time to apply it to the full shot.

• Click Create Inference in the CopyCat node. This generates an Inference node, which is used to process the full sequence.
• Connect your full clip to the new Inference node.
• CopyCat will now auto-generate mattes for every frame, saving you hours of manual roto.

If the results need improvement, refine your training frames, retrain the model, and apply again.

Want to Practice? Download This Free Shot

To get the best results, start with the right kind of footage. This free practice clip of a man crawling through a building is perfect for learning or showcasing your roto skills with CopyCat.

Download the free clip here and start automating your roto workflow!

Full tutorial from The Foundry:

If you're interested in learning Nuke for free, check out our free 6-part introduction to Nuke course.

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