The view banks

The basic detector drawing routines (GDRAW, GDRAWC, GDRAWX) scan the data structure JVOLUM repeatedly to extract position and dimension information on the volumes. This can be a rather lengthy process even on fast computer. Hidden line removal drawing requires an auxiliary data structure and the relative visibility of all the volumes has to be analysed. With complicated detectors the time spent in this process can be substantial, depending on the drawing options chosen and on the speed of the machine on which the program is run. In order to alleviate this problem the graphic banks and the associated routines have been developed.

The interpretation of the structure (for instance scanning of the volumes' data structure to convert the 3D geometry structure into a set of 2D lines, visibility analysis, surface creation or light processing) is thus separate from the drawing itself. In this way, the interpretation is performed only once and all the 2D information is stored in view banks (data structure JDRAW [DRAW399]). These views can then be displayed quickly, having only to draw the 2D vectors or the fill areas previously stored.

For a detector with more than 100 different volumes, for example, this costs only a few thousand words of memory for each drawing stored.

If the drawing routines are called while a view bank, identified by a positive integer, is open (GDOPEN) only interpretation will be made, no output will be generated until the bank is closed (GDCLOS). When a view bank has been closed it cannot be modified, but it can be displayed as many times as wanted (GDSHOW) or deleted (GDELET).

Once a drawing (detectors, tracks or hits) is in a view bank, it is possible to scan it in detail via the LENS or ZOOM interactive commands (only available with X11). For more information see the [XINT] section.

CALL GDOPEN (IVIEW)

IVIEW

( INTEGER) view bank number ( IVIEW>0).

Opens a view bank, used to store 2D graphics information coming from the interpretation of 3D structures (but also 2D annotation). All subsequent calls to the drawing routines will fill the view bank IVIEW, without generating any output. CALL GDCLOS Closes the current opened view bank. Once a view bank has been closed no more drawing can be added to it. A call to GDCLOS also restores the screen.

CALL GDSHOW (IVIEW)

IVIEW

( INTEGER) view bank number ( IVIEW>0).

Displays view bank IVIEW. GDSHOW can be called either before or after a view bank has been closed. If a view bank is currently open, the content of bank IVIEW will be added to it.

      CALL GDOPEN(3)
      CALL GDRAWC('ALEF',2,5.,10.,10.,0.013,0.013)
      CALL GDCLOS
      CALL GDSHOW(3)
      .
      .
      CALL GDXYZ(0)

Figure: Example of use of view banks

CALL GDELET (IVIEW)

IVIEW

( INTEGER) view bank number ( IVIEW>0).

Deletes a view bank from memory. If called before a bank has been closed, GDELET will also restore the screen mode.

Note: the JDRAW data structure has a top level bank which contains one word for each view bank in Q(JDRAW+IVIEW). This word is a key which determines the status of the bank. If this key is 3, the bank itself is protected against deletion, and it cannot be deleted by GDELET. An example of use of view banks is shown in Fig. .

DRAW399