Apple Motion 5.1.1 - Manual (Page 901)

Chapter 20 Shapes, masks, and paint strokes 901
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Replace: Completely replaces the image object’s alpha channel as well as any other masks
that appear beneath the mask in the Layers list. In the following example, the circle mask
overrides the rectangle mask, because the circle mask appears above the rectangle mask in
the Layers list and is set to Replace. For more information, see
Combine multiple masks on
page 892.
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Intersect: Shows pixels only in regions where masks overlap. In the following example, only
the overlapping areas of the rectangle and circle masks are visible.
In another example, if you import a TIFF file with an alpha channel and you want to cut out
part of it without losing alpha information, you must use the Intersect blend mode. This is also
true for layers with keying filters applied.
Intersecting mask cropping unwanted
opaque areas
Original alpha channel from key
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Invert Mask: A checkbox that reverses the mask—its solid and transparent areas are swapped.
This is useful if you need to switch the solid and transparent areas of an existing mask.
Tip: You can apply different filters and effects to the foreground and background of an image
by first masking the foreground subject, duplicating the layer and its mask, then inverting the
duplicate layer’s mask. Effects applied to the background can then be completely isolated from
the foreground, or vice versa. You can adjust the opacity of a mask in the Properties Inspector.
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