Compositing

Compositing is the overlaying of two or more images, one over the other. The primary was to do this is through the use of the alpha channel. The alpha channel is an 8-bit value that indicates the relative transparency of a pixel, with 0 being completely transparent and 255 being completely opaque. Only certain file formats store the alpha channel, e.g. targa files contain 32 bits per pixel, with 8 bits being the alpha channel. JPEG images do not store an alpha channel, but can be used as a background image. Here is an example, from 3D Studio Max, of three images that are composited to create an overall image.

Background image (JPEG) Tutash.jpg (5983 bytes)
Center image (Targa) middle.jpg (4129 bytes)
Front image (Targa) Tutframe.jpg (16204 bytes)
Final Composite Image composite.jpg (18908 bytes)


Main Post-Production Page
HyperGraph Home page.

Last changed February 08, 2000, G. Scott Owen, owen@siggraph.org