(Page 1 of 2 pages for this article  1 2 >)

Filed under: Motion Graphics •Post Production •Visual Effects •

A Track of the Clones

One of the most significant but underused sections of After Effects has to be its vector-based painting engine, introduced back in version 6. One of the capabilities of this engine is the ability to clone one area of a piece of footage onto another area, including cloning from different points in time. As sexy as that sounds, in the real world cloning can quickly become tedious, especially when the object you are trying to replicate (or eliminate) is moving. Fortunately, other features in After Effects – including Expressions and its Motion Tracker - can greatly ease the pain. In this column, we’ll walk through such a task. These same general techniques can probably be applied to other compositing/motion graphics programs as well.

Holes in the sky

In our example, we have a piece of footage shot at an airport with a plane in the foreground, and a second plane in the background taking off. (The shot we’re using is from the Artbeats Establishments: Mixed Cuts stock footage library; if you have it, import clip EM107 and follow along.) The director is concerned that the second plane might confuse the issue of which one the viewer should be paying attention to, and asks if you could “just” remove it from the shot.

Our goal is to remove the second, smaller plane between the control tower and the hero plane (left). Cloning in another piece of sky might result in an obvious spot, as the sky actually consists of a subtle gradation (center). By using a combination of tracking plus cloning from a time-shifted frame, we can ensure we always clone an appropriate piece of nearby sky that follows the smaller plane’s movements (right).

Your first thought might be “there’s a lot of nice, even, blank sky in this shot; I’ll just clone a section of it over the unwanted plane.” But even a fairly even sky such as this one still has subtle variations and gradations, which can make the cloned spot flash out like a beacon (see above). A better approach is to clone the same section of the sky back onto itself, meaning you should have the closest possible match. The trick comes in cloning from a time when the second plane is not present – such earlier or later. To pull this off, make sure your clip has some handle (extra time at the head and/or tail) to be able to clone from. If the clouds move, you may still have some trouble matching their pattern; you will want to clone from the nearest time possible where the plane is not present.

To accomplish this in After Effects, place the footage in a composition, select the resulting layer, and double-click it to open its Layer window. In the Tools palette, select the Clone tool – the shortcut is Command+B on Mac (Control+B on Windows). If the Auto Open Panels option is checked (it defaults to On - look for it above the Comp panel in After Effects CS3), this will open the Paint and Brush Tips panels. Make sure you select a brush large enough to cover the smaller plane. Dial in a feathered edge that is large enough to create a nice blend, but not so large that it causes the plane to be revealed inside these edges. You can dynamically resize your brush in the Layer window by placing the cursor over the object you want to clone, holding down the Command (Control) key, and dragging the cursor to resize the brush’s Diameter. Let go of the Command (Control) key but keep dragging to resize the stroke’s Hardness (feathering amount) – you will see a second circle which shows the size of the feather.

If you wanted to clone from one place in the sky to another, hold down the Option (Alt) key and click on where you want to clone from, then start painting over the plane – if your brush is big enough, one click should do it. Since we want to clone “from” and “to” the same point, just click twice on the plane. Type PP (two P’s in quick succession) to reveal the strokes you’ve made in the Timeline window. Paint will appear as an effect that has been added to the original layer; each stroke will appear as a separate sub-layer. When you’re done experimenting, delete your practice strokes.

Twirl open the Clone stroke’s parameters in the Timeline window, then twirl open its Stroke Options. At the bottom of the list is Clone Time Shift; offset this earlier or later in time until the plane is replaced with clean sky from a time before or after the plane entered this particular point in space.

Life seems cool, until we preview the cloned shot and realize we’ve only fixed one point in space – as the plane flies across the sky, it emerges from behind our cloned sky. Don’t create a new clone stroke for every point in time the plane reappears; you’ll end up with a bunch of strokes, which makes them harder to manage. A better approach is to animate Stroke Options > Clone Position and Transform > Position to make the stroke follow the plane. Best is to make After Effects animate the stroke for you, using its Motion Tracker - which we’ll discuss on the next page.

(Page 1 of 2 pages for this article  1 2 >)

Name:

Email:

Location:

URL:

Smileys

Remember my personal information

Notify me of follow-up comments?

Submit the word you see below: