Using image masks
Motion has the flexibility to allow us not only to create masked shape selections but also to mask any object or group in the Layers tab. Let's take a look at how we can achieve this.
Getting ready
Under the exercise folder of this chapter, double-click on the 06_09 project file. Play back the project; it's a series of animated blurred circles moving across the screen from right to left. In this project, there is also a Video clip layer that has been turned off. Click on the empty square next to it to turn it on. Our goal is to have our video play with the circles onscreen. We can use either the luminance or transparency of the Bokeh group to achieve this.
How to do it...
We're going to add an image mask to the Video layer in this project.
Select the Video layer and from the Object menu choose Add Image Mask, as shown in the following screenshot. An image mask becomes applied to the video image but it needs a source.
Drag the Bokeh group over the top of the image mask in the...
