One of the nice things about Motion is its ability to use Masks in creative ways. We can use all sorts of shapes as an image mask. Best of all, we can animate these to our hearts content. In this tutorial, I'll show you just how flexible this image mask system is when you understand how shapes work.
There are a couple of ways to initiate the creation of a mask. I'd say the most important thing to remember, no matter which method you use, is that they are all simple starting points. In the end, we can manipulate and thus animate them all in the same manner. What are our options for beginning our mask?
The first method is using the Mask Tool. If I highlight an image in the Layers pane, I can go to the Mask Tool in the toolbar. Here we can choose from a variety of shape sources to draw a mask from scratch: rectangle, circle, freehand, bezier, b-spline. This is probably the most direct route to take because when we draw a shape with this tool we are directly drawing a mask right away.
The second method is to right-click a layer in the Layers pane, and chose Add Image Mask from the pop-up menu, or use Shift-Command-M.
This gives us a blank mask for that layer, to which we can apply a shape. F4 opens the Image Mask tab in the Inspector. There is a Mask Source well in the Mask controls. Simply drag a shape layer from the Layers pane into this to apply it. Our shapes can come from any of the following three sources.
Once an Image Mask is created for a layer, we can create a shape in one of three ways. The first method is to use the Shape Tool in the toolbar. From this menu, we can simply draw a shape with the rectangle, circle, or line tools. Once the shape is drawn, hit the Escape key to get out of its edit mode, then turn off its invisibility in the Layers pane. F4 to its Inspector tab and be sure Fill is enabled and Outline is disabled. Then apply it to an Image Mask. We can then select the Image Mask layer in the Layers pane, F4 to see the Shape tab. Then drag and drop the shape layer we just created into the Mask Source well as mentioned above.
Yet another way to draw a shape is with the Bezier / B-Spline Tool in the toolbar. This is similar to the previous method of using the Shape Tool, except we are able to draw more complex, precise shapes. Once you select the tool and draw your shape, hit the Enter / Return key to get out of its edit mode, turn off its visibility in the Layers pane. F4 to open its Inspector tab and be sure Fill is enabled and Outline is disabled. Then drag and drop the shape layer we just created into the Mask Source well as mentioned above.
Finally we can simply go to the Library (Command-2), to the Shapes library, and chose from a very abundant collection of pre-drawn vector shapes. With the appropriate Group selected in the Layers pane, select the library shape you want to start working with, then click the Apply bottom in the preview section of the Library inspector. Once applied to our Group in the Layers pane, turn off its visibility in the Layers pane. Then drag and drop the shape layer we just created into the Mask Source as mentioned above.
Again, it's important to bear in mind each of these methods is simply a way to begin. Once we have an initial shape, we can customize it from there.
Once we have an image mask created and applied to our image, we can now adjust it to taste. No matter what method you use from Step 1, adjusting the shape is the same. If you create the mask shape with the Mask Tool, select the mask layer below the original image in the Layers pane. If you used the Image Mask technique and created a shape by one of the other methods, select the actual shape's layer (keep it invisible, that's ok).
Now that our shape is selected, in the Tool Bar go to the Editing Tools. From this menu select the Edit Points tool. You'll see the bezier points now for your shape. Click one to highlight it. Then drag it anywhere you'd like.
Right-click it to make it Linear (sharp corner) or Smooth (bezier curved corner), or to even lock it so it can't be changed. This applies to every method of creating a shape we've looked at so far. Customize to your hearts content.
For a shape, F4 to open its Inspector tab and experiment with the Roundness control in the Geometry section, and the Feather and Falloff controls in the Style tab. If you drew with the Mask Tool, they are all in the same place when you hit F4.
With the playhead in the timeline where we want our animation to end (it's often easier to work backwards), adjust the shape to its final configuration. Be sure the shape's layer is selected, F4 to the Inspector. If you drew with the Mask Tool, have the mask layer selected, then F4. To the right of the Control Points section header, when you mouse over it, you'll see a gray keyframe diamond. Click it to create a keyframe for all of the shape's points at once. This will manipulate the individual shape points. If you want to move the shape across the frame, or rotate it, then keyframe those parameters in the Properties tab (F1).
Bring the playhead to the point in the timeline you want the animation to begin. Then simply move the shapes points to the configuration you want them to start from. The new keyframe will be created automatically, since you set one for this parameter already. Keep in mind you can also keyframe the Roundness, Feather and Falloff parameters, too.
With these very simple mechanics you can very simply and quickly create, adjust, customize and most importantly animate mask shapes over time in some very complex ways. We duplicate layers and filter each, adjust opacity and apply blend modes to give us some very artistic effects. Another idea is to apply a Behavior to your shape in order to manipulate it in interesting ways. Or when compositing several layers together, why not even use a tracker, perhaps? The possibilities are endless!