"Sets" of almost unlimited size can be created digitally because compositing software can take the blue or green color at the edges of a backing screen and extend it to fill the rest of the frame outside it. More commonly, composited backgrounds are combined with sets – both full-size and models – and vehicles, furniture, and other physical objects that enhance the realism of the composited visuals. Virtual sets are also used in motion picture filmmaking, usually photographed in blue or green screen environments (other colors are possible but less common), as for example in Sky Captain and the World of Tomorrow. In sophisticated installations, subjects, cameras, or both can move about freely while the computer-generated imagery (CGI) environment changes in real time to maintain correct relationships between the camera angles, subjects, and virtual "backgrounds". In other cases, presenters may be completely within compositing backgrounds that are replaced with entire "virtual sets" executed in computer graphics programs. In television studios, blue or green screens may back news-readers to allow the compositing of stories behind them, before being switched to full-screen display. For example, one could record a television weather presenter positioned in front of a plain blue or green background, while compositing software replaces only the designated blue or green color with weather maps.Ĭomposite of photos of one place, made more than a century apart Typical applications Natron) replaces every pixel within the designated color range with a pixel from another image, aligned to appear as part of the original. In the digital method of compositing, software commands designate a narrowly defined color as the part of an image to be replaced. Pre- digital compositing techniques, however, go back as far as the trick films of Georges Méliès in the late 19th century, and some are still in use.Īll compositing involves the replacement of selected parts of an image with other material, usually, but not always, from another image. Today, most, though not all, compositing is achieved through digital image manipulation. Live-action shooting for compositing is variously called " chroma key", "blue screen", "green screen" and other names. The Quartz Compositor takes the events from the queue, determines which process owns the window where the event occurred and passes the event on to the processes own event queue.A composite image of a basketball shot, with six basketballs added to the initial image to depict the arc of the shot.Ĭompositing is the process or technique of combining visual elements from separate sources into single images, often to create the illusion that all those elements are parts of the same scene. Quartz Compositor in its role as window manager, also has an event queue which receives events (key strokes, mouse clicks, etc) from the I/O Kit. ![]() This allows the Mac OS X windowing system to be " agnostic in terms of a drawing model" and gives it the ability to create impressive visual effects, such as the genie effect as a window is minimised to the Dock. ![]() Quartz Compositor then takes each window bitmap and composites them together using the associated information to create a display. The application that owns the window draws the window contents to the appropriate bitmap, using any of the supported drawing modes (for example Quartz 2D, QuickDraw, OpenGL). Quartz Compositor performs two main functions:Įach window in Mac OS X is stored as a bitmap associated with positioning (including z-index positioning), transparency and anti-aliasing information. On a Mac OS X system, the Quartz Compositor can be seen in a process list as Window Manager or, in more recent versions, WindowServer. Quartz Compositor is the windowing system that is responsible for the user interface in Mac OS X.
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