Apple Motion 4 - Manual (Page 1166)

For example, you could apply the Crystallize filter to a mask to stylize its edges. This results
in jagged edges that resemble facets of crystal around the edges.
Original mask (color channel) Original mask (alpha channel)
Crystallize filter applied to alpha channel
(color channel view) Crystallize filter applied to alpha channel
(alpha channel view)
When applying filters to masks, it’s useful to bear in mind that masks are just grayscale
images. In the example above, the Crystallize filter creates patterns in the grayscale mask
image, which results in a rippled translucent pattern.
To apply a filter to a mask
Do one of the following:
µ
Drag a filter from the Library directly onto a mask in the Layers tab or Timeline.
µ
Select a mask in the Layers tab or Timeline layers list, then choose a filter from the Add
Filter pop-up menu in the Toolbar.
The filter appears nested underneath the mask layer to which it’s applied.
1166 Chapter 17 Using Shapes, Masks, and Paint Strokes