Drawing a Volume Projection view -- Case 2

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| Geant 3.15  |               GEANT User's Guide              | DRAW115  ##
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Author(s) : F.Carminati, P.Zanarini                    Submitted: 01.01.86
Origin    : P.Zanarini                                   Revised: 11.12.92
                                  

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|CALL GDRVOL (NNAMS,CHNAMS,LNUMBS,NRS,THETA,PHI,PSI,U0,V0,SU,SV) |
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Draws an orthographic parallel projection or a perspective projection (depending on the option chosen via GDOPT) of the volume CHNAMS(N),LNUMBS(N) with all its descendants, at the position U0,V0 (user coordinates), with the scale factors SU and SV. The object is seen from THETA and PHI angles, and the resulting 2D projection is also rotated by an angle PSI on the screen plane. These parameters, as well as zoom parameters set by GDZOOM, define the current view parameters, and they are copied in /GCDRAW/. Attributes like colour, fill area, line width, line style, visibility, etc. can be set by the GSATT routine for CHNAMS(N) and or its descendants [GEOM 500]. This routine differs from GDRAW in the following aspects:

1. The object to be drawn is identified by a full path. This gives the possibility of drawing a particular copy or division of a volume, or even a volume that has more than one mother in the geometry tree. CHNAMS(1),...,CHNAMS(N) contain the volume names and LNUMBS(1),...,LNUMBS(N), the volume numbers defining the path to go from the top volume to the one to be drawn.
2. The object can be drawn either with respect to the MAster Reference System (NRS=0) or with respect to its Daugther Reference System (i.e. the Local R.S.); in the first case it is drawn in its position in the real world, while in the second one it is drawn like GDRAW would do.
3. In this latter case, track and hit points will be drawn with respect to the DRS of the volume last drawn by this routine, and not with respect to the MARS as is done normally (to reset to the normal case a call with NRS=0 or NNAMS=0 is required).

NNAMS

(INTEGER) number of elements levels in the arrays CHNAMS, LNUMBS. The bottom volume of this path is also the one that is actually drawn;

CHNAMS

(CHARACTER*4) array of volume name (dimensioned at least to NNAMS);

LNUMBS

array of volume numbers (dimensioned at least to NNAMS);

NRS

reference system used:

NRS=0

to have the volume(s) drawn with respect to the MARS

NRS!=0

to have the volume(s) drawn with respect to the DRS

THETA

theta angle between the line of sight and the Z axis of MARS;

PHI

phi angle between the projection of the line of sight on plane X Y and the X axis of MARS

PSI

psi angle by which the projected image will be rotated on the screen plane

U0

u coordinate on the screen of the volume origin

V0

v coordinate on the screen of the volume origin

SU

scale factor for u coordinates

SV

scale factor for v coordinates

Here follows an example of the use of GDRVOL:

 CHARACTER*4 CHNAMS(5)
 INTEGER LNUMBS(5)
 DATA CHNAMS/'OPAL','BRL-','EB  ','EBB ','EBP '/
 DATA LNUMBS/    1 ,    1 ,    1 ,    1 ,   20 /
 - - - - -
 NRS=0
 CALL GDRVOL(5,CHNAMS,LNUMBS,NRS,45.,135.,0.,10.,10.,0.01,0.01)
 CALL GDAXIS(0.,0.,0.,300.)
 CALL GDXYZ(0)
 - - - - -
 NRS=1
 CALL GDRVOL(5,CHNAMS,LNUMBS,NRS,45.,135.,0.,10.,10.,0.01,0.01)
 CALL GDAXIS(0.,0.,0.,300.)
 CALL GDXYZ(0)