Apple Motion 4 - Manual (Page 1100)

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Control-click a handle control point and choose Break Handle from the shortcut menu
to break the relationship between opposing handles.
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Option-drag a broken tangent or Control-click a handle control point and choose Link
Handle from the shortcut menu to lock the angle of the tangents together again. The
tangents now maintain their relationship when moved and rotated.
Note: You can also press Command-Option and drag a control point so the tangents
maintain their broken relationship when moved and rotated.
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Control-click a handle control point and choose Align Handles from the shortcut menu
to align the tangents to a 180-degree angle.
Tip: Press Shift while you adjust a tangent to constrain its movement to 45-degree angles.
To simultaneously modify the handles for more than one control point, Shift-select the
points (on the same spline) and then adjust the tangents.
Important: If Record (automatic keyframing) is enabled, curve adjustments are keyframed,
creating animated shape changes.
Editing B-Spline Control Points
Editing the position of control points in B-Spline shapes is similar to editing Bezier shapes.
In fact, the steps for selecting, moving, adding, deleting, and locking control points are
almost exactly the same. The main difference in editing both types of shapes lies in how
you manipulate and adjust curves.
1100 Chapter 17 Using Shapes, Masks, and Paint Strokes