B-Spline Mask [BSp]
A B-Spline Mask is identical to a Polygon mask in all respects except one. Where Polygon masks use Bezier splines, this mask tool uses B-Splines. Where Bezier splines employ a main point and two handles to manage the smoothing of the spline segment, a B-Spline requires only a single point. This means that a B-Spline shape requires far fewer control points to create a nicely smoothed shape.
The smoothness of a B-Spline is determined by the tension of the control points. To adjust the tension of a B-Spline's control points, select the point, hold down the W key and click-drag the mouse pointer to the left and right to increase or decrease the tension of the curve through that point.
Many of the controls found in this mask tool are common to all mask tools. These controls are documented at Common Mask Controls.
Adding Points to a B-spline effect mask is relatively simple. Immediately after creating the mask there are no points but the mask will be in Click Append mode. Simply click once in the display wherever a point is required for the mask. Continue clicking to draw the shape of the mask. When the shape is complete, click on the initial point again to close the mask.
When the shape is closed, the mode of the polyline will change to Insert And Modify. This allows for the adjusting and adding of additional points to the mask by clicking on segments of the polyline. To lock down the mask's shape and prevent accidental changes, switch the polyline mode to Done using the polyline toolbar or context menu.
When a B-spline mask is added to a tool, a toolbar will appear in the view with buttons that offer easy access to the modes and tools. Hold the mouse pointer over any button in the toolbar to display a tooltip that describes that button's function.
Change the way the toolbar is displayed by right-clicking on the toolbar and selecting from the options displayed in the toolbar's context menu.
The function of the buttons in this toolbar are explained in depth in the Polylines chapter.
Use the Size control to adjust the scale of the B-spline effect mask, without affecting the relative behavior of the points that compose the mask or setting a keyframe in the mask animation.
Use these three controls to adjust the rotation angle of the effect mask along any axis.
The Fill Method drop-down menu offers two different techniques for dealing with overlapping regions of a polyline. If overlapping segments in a mask are causing undesirable holes to appear, try switching the setting of this control from Alternate to Non Zero Winding.
By default, all B-spline masks are animated when they are created. The initial keyframe is set to the current time and any changes to the shape at different times will create new keys.
Right-clicking on this label will display a context menu that offers options for removing or re-adding animation to the mask, or published and connecting the masks together.
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