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26.1.2 Using the Sphere Drawing Commands

The space filling image drawing facility of CONGEN runs its own command interpreter. It is entered by specifying SPHERE to CONGEN. The commands to this facility consist of 2 or 4 letter keywords which may be followed by various arguments. Except for the title command, (see Data Flows for Drawing Spheres), the commands expect their arguments free field. If any arguments are not specified, they will default to 0 unless otherwise noted.

To exit from SPHERE, specify EX or END as a command and you will exit.

When SPHERE is first called, all of its data structures are initialized. Thereafter, leaving and reentering it will not affect anything internal to it. This permits you to construct images of multiple molecules very easily. To initialize everything back to its starting state, use the HO command, see Data Flows for Drawing Spheres.

Since the data structures sphere drawing are used for the PEER command, see Peer Command, the initial display device is a small dummy device that does not require much pixel storage. Therefore, before making a picture, you must also specify an output device size using the DV command or use the various screen size and scale factor commands described in Transformations for Sphere Drawing.

Before invoking SPHERE, you must have read in a PSF, coordinate set, and parameter set; unless you read in a spheres list in which case nothing is needed. Note that if the PSF is changed by a SPLICE command or by an editing command, the HOME command should be executed, see Transformations for Sphere Drawing.