Animating the Range of Key Elements

You animate the tolerance, softness, and patch ranges by changing the range at different frames. In the Animation editor, range changes appear in the Shape channel. You can set a Shape keyframe by:

• Adding or subtracting pixel values from the range by sampling again in the image.
• Adjusting the key elements in the RGB viewer. All transformations made to a key element are applied to its Shape keyframe, including translation, rotation, scaling, and noise analysis.
• Changing the values in the Softness Scaling X, Y, and Z fields.

If you display the convex hull while animating a key element, the convex hull fills the ellipsoid in between keyframes. The sample is recreated to fill the ellipsoid on interpolated frames. This ensures the smoothest possible transition between keyframes.

To display the Animation editor, click the Animation button.

Shape Keyframes

The shape of ellipsoids and patches is defined by their translation, rotation, and scaling values, so the Shape keyframe is actually composed of multiple parameters. The Y value in the Animation editor does not have the same significance as it does for a single parameter (for example, opacity). Instead, the Y value is composed of sequential numbers that represent keyframes that have been set. Each consecutive keyframe is assigned a sequential Y value: the first keyframe has a Y value of 1, the second has a Y value of 2, and so on. Although the Y value does not represent a single value, you can still adjust the curve to tweak the shape.

To animate the range of a key element:

1. Perfect the key at frame 1.

2. Enable Auto Key.

3. Scroll to other frames and, where necessary, adjust the range using any of the techniques provided in this chapter.

   Keyframes are added at each frame where you change the tolerance, softness, or patch range.

   Note: When you set a tolerance keyframe, a softness keyframe is also set. This is because the softness range is always at least as large as the tolerance range. When you set the tolerance range, the 3D Keyer automatically creates a minimum softness range that is equivalent to the tolerance range. When you adjust the tolerance, the softness range is also adjusted to accommodate the change.

4. Optionally, tweak the animation by adjusting the shape curve in the Animation editor. The image updates as you make changes.

Changing the Interpolation

Parameter values in between keyframes are interpolated. Change the type of interpolation using the Animation editor.

The default interpolation for the shape curve is Bézier, which creates a smooth transition between keyframes. If your clip has a very sudden change in the colour values (for example, if a light was switched on at a particular frame), use Constant interpolation between the two keyframes where the change occurs.