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1.9.2 Special Topic: How Graphics Are Output
The details of how Mathematica outputs graphics vary between different computer systems and different Mathematica interfaces. The documentation that came with your copy of Mathematica should tell you what is relevant in your case.
With text-based Mathematica interfaces, each piece of graphics output typically fills your complete screen, or causes a new window to be created which is then filled with graphics. The details of how you get rid of the graphics vary from one system to another. Note that when you start Mathematica with a text-based interface, you may have to load a Mathematica package to tell Mathematica how you want graphics output to be done. The details of this should be described in the documentation that came with your copy of Mathematica.
With a notebook-based Mathematica interface, each piece of graphics is placed in a cell in your notebook. The Mathematica front end allows you to manipulate the graphics in several ways, for example by resizing them, or redisplaying them with different options.
Many Mathematica systems allow you to collect together sequences of graphic images and display them in quick succession to produce an animated "movie". Notebook-based interfaces typically allow you to select a sequence of cells to serve as the frames in your animation. Many text-based interfaces also provide animation capabilities; typically the function ShowAnimation[, , ... ], where the are pieces of graphics output, generates a movie.
You should understand that when Mathematica produces any kind of graphics output, it does so in three stages. The first stage is to execute commands like Plot to produce a sequence of Mathematica graphics primitives. These primitives, to be discussed in Section 2.9, represent objects such as lines, points and polygons as Mathematica expressions. The second stage of producing graphics output is to convert these graphics primitives to a standardized device-independent representation of your graphical image. Mathematica generates this representation in the PostScript page description language.
The final stage of graphics output is to take the PostScript description of a graphical image, and render it on the particular device you want. In a notebook-based interface, the Mathematica front end performs this rendering. On other systems, the rendering is usually done by an external program which is automatically called from within Mathematica.
The importance of using PostScript as a graphics description language is that it can be rendered on many different kinds of devices, including both displays and printers, and it can be imported into many kinds of programs. Specific versions of Mathematica come with various conversion utilities to produce Encapsulated PostScript form, and other standard graphics formats. The command Display["file", graphics, "EPS"] saves the encapsulated PostScript representation of the graphics in a file.
Although most graphics from Mathematica are first converted to PostScript, and then rendered on particular devices, there are some cases where it is more convenient to render directly from the original Mathematica form. One example is on systems that manipulate images of three-dimensional objects in real time. On such systems, the function Live[graphics] is typically set up to produce a "live" version of a piece of Mathematica graphics, which can then be manipulated directly using the various tools available on the particular computer system.