Apple MA434Z/A User Manual - Page 682

Pulling a Bluescreen or Greenscreen In the Key Tool tab, the two primary nodes used to pull bluescreen and greenscreen keys are Primatte and Keylight. In the Shake 4 Tutorials, there are lessons devoted to each. Other functions in the Key tab include the ChromaKey, DepthKey, DepthSlice, LumaKey, and SpillSuppress nodes. These are discussed in the second half of this chapter. The ColorReplace node, although located in the Color tab, is also considered to be another key-pulling node. Note: Although there is a ChromaKey node in the Key tab, it is not particularly useful. The same model and parameters appear in ColorReplace, but ColorReplace generally works much better. Keying With Primatte and Keylight For lessons on how to use Primatte and Keylight to pull keys, see the Shake 4 Tutorials. Keying With ColorReplace ColorReplace is not the best keying tool, but it is a good node for making quick garbage masks. The following example uses ColorReplace to key the blonde image over the clouds1 image. To set up the key example: 1 Click the Image tab and select FileIn. 2 Go to the $HOME/nreal/Tutorial_Media/Tutorial_06/images directory and load the alex_fg.jpg and clouds1.jpg images. (The images are courtesy of Photron.) 3 Create the following tree: 4 Set the following parameters: • ColorReplace node: Click the SourceColor control, then scrub on the bluescreen in the blonde image. Set Replace Color to any other color (it just cannot be the same blue). Also, turn on affectAlpha so that you pull a key. • Invert node: Set the channels to "a" instead of rgba. • Over node: Enable preMultiply. 682 Chapter 24 Keying