As described in the previous chapter, the set of structures in the CSS consist merely of memorized objects. It is necessary to plot them on a terminal to obtain a graphic image.
PHIGURE introduces a wider concept than the terminal : the workstation. This term refers to any physical apparatus or system capable of executing the basic graphics functions in the structures.
A workstation may consist of a screen, a printer, a plotter, a CGM metafile, a print standard file (PostScript, HPGL, etc.), and also a window on an X-Window terminal. It is therefore identified by a type number, which informs PHIGS of the physical and/or logic characteristics of the workstation. The type may also indicate the basic graphics library used by the workstation. For Example : it is possible to set up a workstation using an X-Window or GL library on the physical terminal of the same Silicon Graphic system.
Several workstations of the same type may be used simultaneously by one PHIGURE application. Each workstation has a separate identifier. A workstation identifier is an integer between 1 and 15. In this manual, the variable corresponding to the workstation identifier is always called WS_ID or WKID.
The following steps must be carried out to plot the contents of a list of structures on a workstation :
- open the workstation : this may consist of opening an X-window or a file.
PHIGURE function topen_ws
- inform the workstation which structures in the CSS are to be displayed
PHIGS function ppost_struct
- order the workstation to plot all the structures to be displayed
PHIGS function predraw_all_structs
The set of structures is plotted on a workstation according to a particular point of view selected by means of a PHIGURE view definition function.
Views are specific to each workstation : it is possible to plot structures from a certain point of view on one workstation and from a different point of view on another workstation. It is also possible to plot structures from different points of view on the same same workstation. The different points of view are identified by a positive integer called a view index. A view is then fully identified by the workstation number and the view index.