Apple Motion 4 - Manual (Page 1173)

• Replace: This setting uses the current mask to completely replace the object’s original
alpha channel, as well as any other masks that are applied to the same object that
appear underneath the current mask in the Layers tab. You can add additional masks
above, set to whatever blending mode you like. In the following example, the circle
mask is overriding the rectangle, since it is at the top of the masks that are nested
within the gradient object.
• Intersect: Masks that are set to intersect do not replace an object’s original alpha channel.
Instead, they mask out all regions of the object that do not overlap the mask itself. This
includes other masks applied to the same object that appear nested underneath the
intersecting mask in the Layers tab. In the following example, only the overlapping
areas of the rectangle and circle masks are opaque. Everything else is transparent.
Invert Mask: When this checkbox is selected, the mask is inverted—its solid and
transparent areas are swapped. This is useful if you need to switch the solid and
transparent areas of a mask you have already created.
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 that are applied to the background can then
be completely isolated from the foreground, or vice versa.
Note: You can adjust the opacity of a mask in the Properties tab of the Inspector.
1173 Chapter 17 Using Shapes, Masks, and Paint Strokes