Today’s tutorial is about one of the more advanced features in our HUE Animation software package: Chroma Key. This is often known as ‘green screen’, and it’s the technique used in a lot of major movies and television shows to make people appear as though they’re somewhere else.

The idea is that you completely remove one colour from your scene and replace it with a different colour, background picture or photograph. It’s called ‘green screen’ because most people use a green background and then remove all of the green afterwards.

Why green, rather than red or yellow? There are some technical limitations but on important reason is that when you’re filming people, using a bright green background means that the colour is unlikely to overlap with any of the actors in your film. You can film anything you want with stop motion animation so green might not work if you’re making a movie about a bright green dinosaur. Experiment to learn which background colours work best with your models.

You can even combine Chroma Key with other stop motion animation tricks, such as making a person vanish as the scene suddenly changes, or drawing on individual frames to create effects like teleportation, growing/shrinking, flight, weather changes and more.

So, how do you get started?

Learning how to use Chroma Key effectively might seem scary at first but it’s a cinch when you get the hang of it. For this video tutorial we’ve shown some simple Chroma Key effects you can create without any tools other than HUE Animation Studio and your imagination. For even more complicated effects you might prefer to export your animation frames and edit them in Photoshop or another application, then re-import them into your movie again – it’s up to you!

To recap, first you need to capture some frames of animation as usual. Use a plain-coloured background that’s a different colour from your models.

If you know you’re going to use Chroma Key, make sure that the lighting is even with no shadows. You might need to add some extra lamps around your film set to remove all of the dark areas. Once you’ve captured enough frames, double-click on one or use the Edit Frame button marked in yellow below.

In the Edit Frame window, click ‘enable’ to activate Chroma Key mode. Next, click the small box next to the ‘enable’ button to choose the colour you want to remove from the picture. Here, we’ve chosen the dark green colour in the background of the frame because we want to replace it with a different background image.

If there are shadows in your background you might see that the background doesn’t completely disappear. Use the Key Range Control slider at the bottom of the Chroma Key controls to adjust the sensitivity – moving it to the right will remove more shades of green from the picture. When you’re done, your screen should look something like this:

The red colour means that the background is empty. So click the big grey box in the Chroma Key controls to choose a picture saved on your computer. The red will disappear, and your picture will show up instead!

If you find that there are some jagged edges or areas which aren’t showing the new background properly, there’s a solution. Click the Chroma Key Reveal tool as shown below. It’s a special kind of eraser which you can use anywhere on the frame to reveal the picture underneath. Don’t forget to adjust the size of the eraser in Tool Properties on the left!

Any questions, or suggestions for new tutorials? Please leave us a comment (or send us a message) and we’ll try to help.