Adobe After Effects CS3 - Manual (Page 272)

AFTER EFFECTS CS3
User Guide
267
When you use the Pan Behind tool to pan a layer behind a mask, the mask’s position remains constant in the Compo-
sition panel but changes in the Layer panel. The masked layer’s Position values change in relation to the composition.
As you pan past the edges of the layer’s frame, the layer’s Mask Path values also change. Using the Pan Behind tool
saves steps; without it, you would have to change the masked layer’s Position and Mask Path properties manually. You
can animate a layer panning behind another layer by setting keyframes for the masked layer’s Position and Mask Path
properties.
When you use the Pan Behind tool in the Composition panel, After Effects automatically makes two adjustments. In the Layer panel, the mask
is moved in relation to its layer (top), and in the Composition panel, the layer is moved in relation to the composition (bottom).
Move a mask
1 Select the mask or masks you want to move.
2 In the Composition panel, drag the mask or masks to a new location. To constrain the movement of the mask or
masks to horizontal or vertical, hold down Shift after you start dragging.
Pan a layer behind its mask
1 Select the Pan Behind tool in the Tools panel .
2 Click inside the mask area in the Composition panel and drag the layer to a new position.
Apply motion blur to a mask
Motion blur creates a blur based on a mask’s movement in the composition. You can apply motion blur to individual
masks. The composition’s Enable Motion Blur switch must be selected for any layer or any mask within a layer to
exhibit motion blur.