Apple Shake 4 Tutorials Uživatelský manuál stáhnout pdf (Strana 103)

Chapter 3 Depth Compositing 103

To color correct the balloons image:

1 In the Node View, select balloons, then insert a Color–Add node.

2 In the Add1 parameters, click the Color control to open the Color Picker.

3 In the Viewer, scrub over the dark orange horizon in the city_/jointfilesconvert/1578512/bg image to add an

orange tint to the balloons image.

Everything from the balloons to the background turns bright orange—and check out

the artifacts around the edges! This is obviously not good.

The entire image is brightened because you’ve color corrected a premultiplied image.

The Color–Add node adds whatever color you choose to the pixel values of all channels,

including the alpha. This returns incorrect pixel values—and the corresponding

transparency values—when multiplied with the alpha channel.

The result is a compromised alpha which generates a tinted matte, rather than the full

transparency we need for the balloons image.

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Apple Shake 4 Tutorials Uživatelský manuál Strana 103