2017

applying motion blur to the mask, which has animated position and rotation values to match the car's
movement, appropriate blurring of the car's edges into the background clip occurs.
TIP Besides the practical use of blurring a garbage mask, that is, to match the movement of an object you are
keying, you can try blurring masks for artistic effects in multi-layered composites.
To apply motion blur to a garbage mask:
1 Access the Garbage Mask Setup menu.
2 Set the motion blur as follows.
Motion Blur button Enable to apply motion blur to garbage masks.
Phase field Specifies whether the motion blur is based on the movement before or after the current
frame. A value of -100 places the motion blur before the frame, while a value of 100 places the motion
blur after the frame. A value of 0 is centred, which evenly distributes the motion blur. The default
value is 0.
Shutter field Controls the duration of the motion blur at each frame, which affects the size of the
motion blur. Increasing Shutter value does not increase the processing time.
Samples field Determines the quality of the motion blur produced by the number of samples taken
at each frame. Increasing the Samples value causes the processing time to increase linearly.
NOTE You can animate the Motion blur button, as well as the Phase, Shutter, and Samples fields. They can
be found in the Channel Editor under the motion_blur folder.
Motion Blur curve Determines the transparency of the samples that create the blurring effect. The
left side of the curve controls the samples of the incoming movement of the subject in the frame. The
right side of the curve controls the samples of the outgoing movement of the subject in the frame.
For example, to add blur to the left edge of the mask as it travels from left to right in the clip, adjust
the motion blur curve so it slopes down. If you want to add a bit of blur on each side of the mask,
adjust the motion blur curve so it peaks in the middle.
Select one of the three vertices on the curve to move it. When you select a vertex, its tangent handle
is displayed. You use the tangent handle to adjust the slope of the curve.
NOTE The garbage mask motion blur settings are similar to those in the Axis menu in Action.
Motion blur occurs on the mask according to the settings you select and the speed its vertices traverse
the clip.
3 Enable Motion Blur. This makes the motion blur available for application on any garbage mask or axis
in the setup.
762 | Chapter 18 Masking and Rotoscoping