[ This article was first published in the January, 2005, issue of
Larry’s Final Cut Pro Newsletter. Click here to subscribe. ]
A few months ago, I wrote about how to use traveling mattes to hide a portion of an image. Recently, while editing an opening for a client, I needed to use a traveling matte to reveal portions of an image. This technique shows you how.
A traveling matte is an effect that reveals, or hides, part of an image based upon the contents of an underlying layer. The most common use of a traveling matte is to put moving video into letters of text. However, in this case, we will create something a little trickier — a spotlight effect that travels across the screen along with the subject of the video. In this case our subject is, yup, you guessed it, a train.
Just to make this even more challenging, in addition to moving the spotlight across the frame, I’ll also increase the size of the spotlight from small at the start to larger at the end.
Here’s how it works:
- Edit the clip containing your subject to the Timeline
- If audio and video are linked, hold the Option key down and click on the video clip to select it
- Type Option -> Up arrow to move the video clip up one track
- From the Generator menu in the lower right corner of the Viewer, select Shape -> Circle
- Edit the shape onto track V1 of the Timeline and make it the same length as the clip on V2
- Select the clip on V2 and choose Modify -> Composite modes -> Travel matte-Luma. This reveals any part of the clip on V2 which is over the white circle, and hides all parts of V2 that are over the black background.
- Click the Controls tab and set a Size keyframe at the beginning of the clip. Adjust the size to 15%.
- Click the Motion tab and set a Center keyframe at the beginning of the clip. Click the cross-hairs button, then click and drag the circle in the Canvas until it reveals the train engine in the distance.
- Move the Playhead in the Timeline until the engine is at it’s ending position.
- Set a new Center keyframe in the Motion tab, click the cross-hairs button, then click and drag the circle in the Canvas until the circle reveals the ending position of the engine.
- Finally, click the Controls tab and create a new Size keyframe at the current position of the Playhead. Change the size to 50%.
When you play the clip, the circle will track across the screen as the engine moves, growing larger as the engine grows larger.
As an advanced tip, if you want to make this really look like a spotlight:
- Move the clips on V1 and v2 up one track to V2 and V3. Copy the clip on V3 and paste it into V1
- Turn on clip overlays at the bottom left of the Timeline
- Drag the opacity of the clip on V1 to 40%.
This is an easy way to create the effect of a moving spotlight, or to reveal portions of an image based upon the shape of a white graphic below it, all using a traveling matte.