Effect: Composite

Description
Layers one clip on top of another, using a provided mask.

Controls

Mode:

Determines how the A and B clips are be composited. The clips can be placed one over the other, added, subtracted, or averaged together. In all cases, the mask determines the extent of the operation for each pixel of the image. As usual for masks, the brighter (whiter) the pixel on the mask, the greater effect the operation has at that pixel on the clips.

Notes
To use this effect, place THREE clips of the SAME EXACT LENGTH in the timeline, next to each other. These are, in order, the A CLIP, the MASK, and the B CLIP. Select the first clip and apply the effect.

NOTE: In previewing, a few frames at the beginning and end of the clip may appear incorrect. This is due to a known bug in iMovie 2. However, the final result using an Apply will be correct in all cases.

Examples

A Clip	Mask	B Clip	A Over B	B Over A	A Plus B	A Minus B	A Avg B