Apple Motion 2 - Manual (Page 868)

868 Chapter 12 Using Shapes and Masks
Image: An image well that assigns a shape, text object, image, movie, or numbered
image sequence to use to mask an object.
Frame: When you use a movie or image sequence as the assigned image, this slider
allows you to select the start frame for playback.
Hold Frame: When you use a movie or image sequence as the assigned image, turning
on this checkbox freezes the frame specified in the Frame parameter. That frame is then
used as the mask for the masked object’s total duration.
Offset: Offsets the X and Y values of the mask’s position, relative to the object it’s
masking. This allows you to change which part of the object is masked.
Wrap Mode: If an image mask is smaller than the object to which it’s been assigned,
you can increase the area it affects by selecting a wrap mode.
• None: The object is used as is.
• Repeat: The object is duplicated and tiled to fill up the full width and height of the
image.
• Mirror: The object is duplicated, tiled, and reversed to fill up the full width and
height of the image. This may create a more seamless repetition for some images.
Source Channel: Lets you choose which channel of the assigned image is used to
create the mask. There are five choices.
• Red: Uses the red channel as a grayscale mask.
• Green: Uses the green channel as a grayscale mask.
• Blue: Uses the blue channel as a grayscale mask.
• Alpha: Uses the alpha channel from the mask object.
• Luminance: Uses the aggregate luminance from the red, green, and blue channels
as a grayscale mask.
Mask Blend Mode: A pop-up menu that determines how an image mask interacts
with the alpha channel of the object to which it’s applied. When an object has multiple
image masks, each mask can have a different Mask Blend mode. When this happens,
each mask adds to, or subtracts from, the object’s alpha channel according to the
selected mode. The final alpha channel is the combined result of all the image masks
that are applied. These modes are identical to the Mask Blend Mode options available
for shape masks. The four options are:
• Add: This is the default selection for new masks. The mask is added to the alpha
channel. This is useful for adding back regions of an image that other masks are
cutting out.
• Subtract: Subtracts a mask from the alpha channel. This is useful for creating holes
in the middle of objects, or for masking out additional regions of an image that are
untouched by other masks.
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