Apple Shake 4 Tutorials - Manual (Page 93)

Chapter 3 Depth Compositing 93
Working With Z Channels
Most compositing depends on the information in the R, G, B, and alpha channels to
create a final composite. An optional channel, called the Z channel, stores depth
information as a grayscale image. Unlike the alpha channel or a rotoshape, the Z
channel represents perceived distances from the viewing plane and image masks in
varying degrees, allowing elements to appear in front of and behind other elements in
the composite. Lighter values are interpreted as being closer to the viewing plane.
Progressively darker values indicate increased distance from the viewing plane.
Launching Shake Projects From Terminal
Here’s something you can try to speed up your workflow in Shake: Open a Terminal
window and enter simple commands that perform the compositing functions before
you launch the Shake interface.
The following steps provide an alternative way to read images into Shake:
1 Open Terminal, found in the Applications/Utilities folder.
2 In the Terminal window, type the following:
cd nreal/Tutorial_Media/Tutorial_03/images/depth
The “cd” command tells Terminal to change directories according to the specified
path.
3 At the Terminal prompt, type:
shake balloons.iff city_bg.jpg city_bg_depth.jpg -gui
4 Press Return.
The “shake” command tells Terminal to read in three image files, and the “-gui”
command at the end of the line prompts Terminal to open the Shake graphical user
interface.
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