Apple Motion 5.1.1 - Manual (Page 904)

Chapter 20 Shapes, masks, and paint strokes 904
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Open the HUD (press D or F7 if the HUD is hidden), then drag the layer to use as the mask into
the Mask Source well.
Important: Click and drag in one movement to successfully drop a layer in an image
well. If you select the layer to use as the source, then release the mouse button, you lose
the selection.
In this example, text is used as the mask layer.
4 Choose the channel you want to use to create transparency from the Source Channel pop-up
menu (in the Image Mask Inspector), as well as any other options necessary to create the
required transparency.
Image mask controls in the Inspector
After you add an image mask to a layer, the following parameters become available in the Image
Mask Inspector.
The Image Mask HUD contains the Mask Source, Source Channel, Mask Blend Mode, Invert Mask,
Stencil, and Stretch parameters. These controls, and the additional parameters in the Inspector,
are described below.
Parameters in the Image Mask Inspector
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Mask Source: An image well that assigns a layer (a shape, text, an image, a movie, particle
emitter, numbered image sequence, and so on) to use to mask a layer.
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Frame: A slider, available when you use a movie or image sequence as the assigned image,
that sets the start frame for playback.
•
Hold Frame: A checkbox, available when you use a movie or an image sequence as the
assigned image, that freezes the frame specified in the Frame parameter. That frame is then
used as the mask for the masked layer’s total duration.
•
Offset: Value sliders that offset the X and Y values of the mask’s position, relative to the layer
being masked, allowing you to change which part of the layer is masked.
•
Wrap Mode: A pop-up menu that increases the area an image mask affects (if the image mask
is smaller than the layer it is assigned to). There are three options:
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None: The object is used as is.
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Repeat: The object is duplicated and tiled to fill up the full width and height of the image.
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Mirror: The layer 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: A pop-up menu that sets which channel of the assigned image is used to
create the mask. There are five choices:
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Red: Uses the red channel as a grayscale mask.
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Green: Uses the green channel as a grayscale mask.
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