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Of course, extracting a mask using strokes is only the first part of creating a useful mask. The Quality, Consistency, and Smart Refine controls let you refine the stroke analysis of the image to create the best tradeoff between performance and quality for the type of mask you need. These controls work hand in hand with the strokes you draw to extract a mask. A set of Mask Finesse controls then let you adjust the resulting mask to manipulate and soften it, to better suit whatever adjustment you’re trying to make. All of these controls are described earlier in this section.
Managing Strokes in the Stroke List
When you draw a stroke, it appears in the Stroke list. By default, all strokes last for the duration of the clip to which they’re applied, so if you draw a stroke to identify a figure that’s not moving, there’s no requirement to motion track the stroke. Strokes in Person mode appear in one long list, while strokes in Features mode appear hierarchically, with the strokes for each feature separated by the title of each feature. Once a stroke appears in this list, it has the following controls.
— Enable/disable feature: In Features mode, once you draw at least one stroke to identify that feature, the title of that feature appears, underneath which is organized all the strokes for that feature. A toggle next to the feature name lets you turn that feature’s contribution to the overall mask on and off.
— Enable/disable stroke: Each individual stroke in this list has a blue dot that lets you turn that stroke’s contribution to the overall mask on or off.
— Stroke Timeline Area with Stroke Tracks: The stroke track for each stroke lets you keep track of and manipulate the animation of strokes to follow camera and subject motion. Blue or red frames in this track let you see at a glance how much of each stroke has been motion tracked; blue frames for positive strokes, red frames for negative strokes. You can also use these tracks to identify frames where you’d like to mute that stroke’s contribution to the final mask and to keep track of which frames have been muted. You can draw a bounding box within the stroke track around however many frames of however many strokes for which you want to delete motion tracking.
Stroke Duration
When you first draw a stroke, that stroke has a duration of one frame, located at the timecode position of the playhead when you drew it. If you move the playhead to the left or right, you’ll see the stroke disappear. If you want one or more strokes to continue analyzing the subject for the duration of that shot, you need to use the Motion Tracking controls to track the stroke to follow along with the motion of whatever it’s drawn on top of. As a stroke is tracked, its duration increases to cover the entire range of tracked frames. If at any point a stroke outlasts its usefulness, such as when a person walks off frame, you can stop tracking that stroke when it’s no longer necessary and it will stop contributing to the analysis.
This is useful, because often you’ll want to place strokes to deal with analysis issues that only last for a few frames, to fix a hole in the mask that only appears briefly. Just be aware, you can’t simply draw a stroke and move on to the next shot; you must track at least one stroke to last for the duration of a subject’s time on screen for that subject to be continuously masked.