Apple Motion 3 - Manual (Page 1114)

1114 Chapter 12 Using Shapes and Masks
Matte Choker: This filter, found in the Matte subcategory of the Filters library, increases
or decreases the semi-transparent area of a layer’s alpha channel by performing a
gamma correction (similar to the Gamma color correction filter) to all regions of the
alpha channel falling between solid black and solid white. This allows you to widen or
narrow the semi-transparent areas within a layer, while leaving all 100 percent solid and
transparent areas unaffected. Once you’ve added a Matte Choker to a layer, the
following parameters become available in the Filters tab of the Inspector:
 Edge Thin: A slider that allows you to modify the edges of the matte. Higher positive
Edge Thin values eat into the alpha channel, eliminating fringing around the edges
of translucent areas. Negative values fill in translucent values, filling in holes and
widening the matte into areas of fringing.
 Feather: A slider that allows you to adjust edge translucence. Lower values reduce
the amount of translucence in a matte, but this results in harder edges around holes
and edges in the alpha channel.
 Mix: A slider that sets what percentage of the original image is blended with the
filtered image. Values range from 0 to 100%.
Keyed original object (color channel) Keyed object with holes (alpha channel)
Keyed object with Matte Choker
(color channel) The Matte Choker eliminates the holes
(alpha channel).