The Garbage Matte in Motion

Sometimes the static garbage matte is sufficient to cover up the bulk of unwanted material, leaving only a small portion of the footage to be retouched. In this example, sections of the footage where the actors are off the edge of the blue screen are at both the beginning and the end of the motion path. We will add some solid blocks of color that can be moved to fill in the largest gaps, so only the first and last few frames will need to be rotoscoped.

1. Add a solid layer (Layer > New > Solid, or F/Ctrl+Y), and set the dimensions small enough to quickly resize and position where needed. Set the color of the

layer to match the garbage matte, using the Eyedropper in the dialog box. Resize and position the solid layer as close to the right side of the actors as possible. Duplicate the solid layer three more times (Edit > Duplicate, or F/Ctrl+D). Move and resize each layer to fit over the largest area of background to cover it up without getting too close to the characters. Position one layer on the bottom side of the actors and two in the top-left corner, completely covering up the exposed area (Figure 6.5).

Select all of the solid layers in the Timeline, press the P key to open the Position settings, and select the Stopwatch on each layer to set the initial position of the layers.

Figure 6.5

Create solid layers that can be animated to follow the characters' motion path and fill in the exposed areas off the blue-screen tarp.

Figure 6.5

Create solid layers that can be animated to follow the characters' motion path and fill in the exposed areas off the blue-screen tarp.

Select just the two bottom-right layers, move the Indicator on the Timeline down a few frames, and drag the solid layers to follow the actors' motion path to close up the exposed area. Continue a few frames at a time, trying to cover as much unwanted material as possible until the gap is completely filled (Figure 6.6).

Move the Indicator toward the end of the actors' motion path, just until they touch the edges of the upper-left solid layers, and then back off one frame so they don't touch. Click the Set Marker box for both layers in the Timeline. Move the layers just ahead of the actors every few frames—just the opposite of the movements made in the lower-right solid layers (Figure 6.7). Save the After Effects project file.

Note that the main middle section of the blue-screen footage has a clean and clear background and needs no further retouching or roto work—the garbage mattes have done the bulk of the work. However, the first one or two seconds of footage, as well as the last, need to have work done on them.

Move the Work Area slider from start and finish to capture just the last couple of frames that need to be exported and worked on. Render out a noncompressed full-size QuickTime movie of the Work Area, and repeat the process for the opening sequence of the footage. View the rendered movies in QuickTime Pro (Figure 6.8).

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Figure 6.6

Move the solid layers to follow the actors' motion path to close up the exposed area off the edge of the chroma tarp.

Figure 6.6

Move the solid layers to follow the actors' motion path to close up the exposed area off the edge of the chroma tarp.

Figure 6.7

Repeat the process with the solid layers on the actors' exit path, but in reverse motion.

Figure 6.7

Repeat the process with the solid layers on the actors' exit path, but in reverse motion.

Figure 6.8

Render only the Work Area of the section of footage that needs roto work to a QuickTime movie.

Figure 6.8

Render only the Work Area of the section of footage that needs roto work to a QuickTime movie.

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