The Static Garbage Matte: Defining the Matte's Boundaries

Defining precisely where the boundaries of the garbage matte need to be placed depends on the extreme motion path of your actors in the frame. You will need to define the beginning and end of their path, as well as how far outside of a straight line in that path that they venture—including any extremities or props used in the scene.

Note: The work in this chapter requires the upgrade to QuickTime Pro, not QuickTime Player. Pro is available from Apple for less than $30.

1. For this project, we'll start with the QuickTime movie file, WalkingBluescreen.mov, located on the DVD in the Chapter 6 folder. Open this movie file in QuickTime Pro (Figure 6.1).

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Figure 6.1 Open the movie file in QuickTime Pro to set up the edge definition process.

2. Start from Frame 1 and copy the frame to the clipboard (F/Ctrl+C), and then create a new file in Photoshop, using the dimensions from the clipboard.

3. Paste the image into the Photoshop file, which will become Layer 1 in the Layers palette.

4. Return to the QuickTime movie and drag the playback Indicator to the position where the actors stop briefly, bend over, and look off to the lower-left side of the frame. This will be the extreme lower-left position defined in our garbage matte. Make sure to scrub the Indicator back and forth to locate the exact frame that moves into the extreme position, and copy it to the clipboard.

5. Return to Photoshop and paste the frame into the file we've created, as Layer 2 in the Layers palette. Set the Blending Mode for Layer 2 to Darken (Figure 6.2). This will allow the placement of the actors from the previous frame to show through so both will be visible to trace.

Figure 6.2 Paste the new layer over the old and set the Blending Mode to Darken to expose the layer below.

6. Continue this process with a few more frames that take the actors outside a direct path from beginning to end, including the last frame—giving you several reference layers.

7. Create a new layer on the top. Use the Lasso tool with a 10-pixel feather to roughly draw an area around the entire path of your characters, creating a large, oblong selection. Invert the selection (F+Shift+I/Ctrl+Shift+I) and fill with a solid color that matches the existing blue-screen background, using the Eyedrop-per to select the color as necessary (Figure 6.3).

8. Save the PSD file with the layers intact, because this is the static garbage matte that will be imported into After Effects.

9. Create a new project in After Effects, as a composition 640 x 480 NTSC, 11 seconds in length. Import the movie file, WalkingBluescreen.mov, and only the top garbage matte layer of the PSD file you just created (or use the file BluescreenMatte.psd, also found on the DVD).

10. Drag both files from the Project window to the Comp 1 window, with the garbage matte layer on top (Figure 6.4).

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Figure 6.3 Select a rough area around the actors and fill the surrounding area with a solid color of the blue-screen background.

This completes the static portion of the garbage matte. Scrub the Indicator in the Timeline window to verify that the garbage matte layer doesn't interfere with the motion path of the characters in the movie. If there is an error in your matte, then simply edit the original file (Edit > Edit Original, or F/Ctrl+E) to make corrections.

Figure 6.4 Import the blue-screen movie file and the garbage matte layer into a new After Effects composition.

Figure 6.4 Import the blue-screen movie file and the garbage matte layer into a new After Effects composition.

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