| Routine ID: GEOM130 | |
|---|---|
| Author(s): | Submitted: 29.09.83 |
| Origin: R.Brun, A.McPherson | Revised: 18.11.93 |
CALL GSDVN (CHNAME,CHMOTH,NDIV,IAXIS)
Divide a volume in a given number of parts along a direction.
The volumes resulting from a division are true volumes in the GEANT sense, with the only limitation that they cannot be positioned. They can have daughters and they can still be divided in turn. Different divisions are distinguished by a different division number, much the same as different copy of the same volume by the copy number. Every operation performed on a division cell (positioning or further division), is automatically propagated to all divisions cells of the same mother.
The kind of the division is indicated by the IAXIS argument.
The
allowed values of IAXIS and the resulting divisions are shown in
figs. 
, , ,
, where the pictures in the first column correspond to
an IAXIS value equal to 1, the second column to IAXIS = 2,
and the third column to IAXIS = 3 respectivly.
The
basic constraint imposed by the GEANT geometry is that the result
of a division is a volume which can be described in terms of the basic
shapes.
The local coordinate system of the divisions is parallel to the system of the mother in case of divisions obtained by parallel planes or concentric divisions. In the case of parallel axes the coordinate system is shifted so that it is in the centre of the division. In case of divisions produced by planes passing through the axis of a volume with axial symmetry ( TUBE, TUBS, CONE, CONS, PGON, PCON, SPHE), the local coordinate systems will be rotated so that the x axis passes through the centre of the division.
This routine allows the user to generate a large number of identical volumes filling a defined volume. The material of the slices is inherited from the mother.
It may happen that the different divisions of a volume have different dimensions. In this case, if a volume has to be positioned in each division, its dimensions must be different according to the division number. This can be obtained in some special cases giving to the dimension of the volume which has to vary in order to fit into the different mothers, the value of -1 in the call to GSVOLU which defines it. As explained in [GEOM050], GEANT will take care to assign to this dimension the maximum value in order to fill the current mother.
What can be done with division can be done also, in most cases, explicitly positioning all the copies. Users must be aware, however, that divisions offer the best performance in tracking of all GEANT geometrical constructs, and they should be used instead of positioning whenever possible in the definition of objects.
Figure: shapes BOX, TRD1, TRD2
Figure: shapes TRAP, TUBE, TUBS
Figure: shapes CONE, CONS
Figure: shapes PARA, PGON, PCON