Autodesk 62205-051408-9001 User Guide - Page 622

23 Keying Keying in Combustion gives you fine control over basic keying procedures, as well as several methods for extracting a matte and finessing it to fix edge issues and spill problems. About Keying Keying is the process of isolating a region of an image by isolating pixels of a particular color and making those pixels transparent. The main purpose of using the keyer tools in Combustion is to generate mattes and remove color spill from a shot. Although you can pull a simple key using the Linear Keyer, sometimes you need greater control over the various steps of the process. In such cases, use the Discreet Keyer or the Diamond Keyer. Keying Concepts Understanding when and how to use a keyer tool or keying feature is fundamental to an artist's efficiency and effectiveness. Having a good grasp of the following keyer concepts ensures the tools provided are used in the most efficient way to produce the cleanest and most convincing result. Mattes A matte is an image used to define or control the transparency of another image. When you pull a key, you generate a matte that defines the transparency of the front source. There are several types of mattes. Articulate matte-A matte whose shape changes over time and is designed to accurately follow the contours of the object to which it corresponds. Complementary matte-The matte that results when the primary matte is inverted. Difference matte-A matte created by subtracting an image in which the subject is present from an otherwise identical image in which the subject is not present. Edge matte-A matte that includes only the outlines or borders of an object. Fixed or static matte-A matte that does not change position or shape over time. Garbage matte-A matte that isolates unwanted elements from the primary element in an image. Garbage mattes are also referred to as garbage masks. Hold-out matte-A matte that prevents a foreground element from completely obscuring an object in the background. Travelling matte-A matte that changes position or shape over time. Color Models A color model is a means of identifying colors in a source according to its component parts. Channel-This color model defines pixels according to the red, green, blue, or custom color extracted from the source image. HLS-This color model defines pixels according to the hue, luminance, and saturation values. Luma-This color model defines pixels according to the luminance value. RGB-This color model defines pixels according to red, green, and blue channel values. RGBCMYL-This color model defines pixels according to red, green, blue, cyan, magenta, and luminance values. YUV-This color model defines pixels based on the luminance and chrominance values. 606