FLUKA: GEOBEGIN
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GEOBEGIN
Starts the geometry description
See also GEOEND, PLOTGEOM
WHAT(1)
: >0 switches on online parenthesis expansion.
If during expansion at initialization the length of an
expression (measured in number of terms) exceeds the
original length by a multiplicative factor NINT(WHAT(1)
),
expansion is aborted and online parenthesis expansion is
used.
WHAT(2)
> 0.0 : absolute accuracy parameter (Aa) in units of 1.E-6 cm.
It is used for tracking and boundary identification. Aa
should be larger than Ar*L , where L is the largest
coordinate value in the geometry description (excluding
the outer blackhole shell containing it) and Ar is the
relative accuracy achievable in double precision (of the
order of 1.E-14 - 1.E-15).
Default
= 0.0001
WHAT(3)
> 0.0 : logical unit for geometry input. The name of the
corresponding file must be input on the next card if
WHAT(3)
is different from 5. Note that values of WHAT(3)
/= 5.0 and < 21.0 must be avoided because of possible
conflicts with FLUKA pre-defined units.
<= 0.0: set to default value of 5.0 (input follows).
Default
= 5.0 (i.e. geometry input follows)
WHAT(4)
> 0.0 : logical unit for geometry output. If different from 11,
the name of the corresponding file must be input on the
next card if WHAT(3)
= 0 or 5, otherwise on the card
following the next one (which contains the filename from
which the geometry is read). Values of WHAT(4)
/= 11.0 and
< 21.0 must be avoided because of possible conflicts with
FLUKA pre-defined units.
<= 0.0: set to default value of 11.0 (output to standard
output).
Default
= 11.0 (i.e. geometry output is printed on
the standard output)
WHAT(5)
: parentheses optimisation level = i0 + i1 x 1000
i0 = 1: logical optimisation only activated
2: logical + "plane" optimisation activated
3: logical + "plane" + "bounding box"
optimisation activated
(Default
: 3)
i1 > 0 forces optimisation even if no parentheses
are found in the region under scrutiny
(Default
: 0)
WHAT(6)
: if > 0 it indicates the number of geometry output
lines to be skipped before starting writing
debugging lines. Please note that the output
can rapidly become huge
SDUM
= COMBINAT : Combinatorial geometry is used. See section
on Combinatorial Geometry for input description
Other geometries, available in older versions of
FLUKA, are no longer supported.
Default
: COMBINAT
SDUM
= COMBNAME : Combinatorial geometry is used in free format, and
names can be used instead of body and region numbers
SDUM
= FLUGG : The FluGG interface to the Geant4 geometry is used.
In this case, the GEOEND card must immediately follow
the GEOBEGIN card. The FluGG interface is available
and described on the fluka web site
Default
: COMBINAT
Default
(option GEOBEGIN not given): not allowed! GEOBEGIN and
GEOEND must always be present.
Notes:
1) Geometry input and output:
i) If WHAT(3)
and WHAT(4)
are both =< 0, the geometry input and
output are part of the standard I/O streams: the GEOBEGIN
card must be immediately followed by the Combinatorial
Geometry input, and then by GEOEND. (See Example 1 below).
ii) If WHAT(3)
is > 0 (and not = 5) and WHAT(4)
is =< 0, GEOBEGIN
must be followed by one card with the name of the CG input
file, and then by GEOEND. (See Example 2 below).
iii) If WHAT(4)
is > 0 (and not = 11) and WHAT(3)
is =< 0, GEOBEGIN
must be followed by one card with the name of the CG output
file, then by the CG input, and then by GEOEND. (See Example 3 below).
iv) Otherwise, if WHAT(3)
is > 0 (and not = 5), and WHAT(4)
is > 0
(and not = 11), GEOBEGIN must be followed, in the order, by
a line with the name of the CG input file, another line with
the name of the CG output file and the GEOEND card.
(See Example 4 below).
The first part of the CG output (9}) is essentially an echo of the
input, and gives in addition some information on storage allocation
of body and region data. Then follow an "Interpreted body echo" and
an "Interpreted region echo", useful in the case where free
geometry input format has been requested. It is recommended to
check on this output that the geometry description has been
correctly reproduced, especially if fixed input format has been
chosen, since column alignment errors are critical due to the CG
strict input format. In case of severe error ("next region not
found", or similar) the CG output will also contain all error and
debugging messages. Minor tracking problems, however, are reported
on the error message file (logical unit 15, see Chap. 3} and Sec.
9.4}, unless reporting has been de-activated by setting
WHAT(6)
<= 0.0.
2) Special algorithms have been implemented in the Combinatorial
Geometry package of FLUKA in order to minimise tracking errors
due to rounding, to improve tracking speed and to handle
charged particle transport near boundaries and in magnetic
fields.
3) A voxel geometry is also available in FLUKA 8.3}.
It is fully integrated into the FLUKA CG and it is even possible
to describe a geometry partly as made of voxels and partly
of conventional CG regions.
4) Information on how to set up Combinatorial Geometry input is
given in Chap. 8}
5) End of geometry information must end with a GEOEND card.
The same card can also be used to activate a geometry debugger.
6) Option PLOTGEOM allows to draw sections of the geometry on
planes specified by the user.
7) Only one GEOBEGIN card is allowed.
8) The WHAT(2)
parameter might need to be increased in case of very
large geometries (i.e. L> 100 m).
Example 1:
* CG Input follows, output is printed as part of Main Output
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
GEOBEGIN 0. 0. 0. 0. 0. 0.COMBINAT
Example 2:
* CG Input read from file BigHall.geo, output printed as part of Main Output
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
GEOBEGIN 0. 0. 25. 0. 0. 0.COMBINAT
BigHall.geo
Example 3:
* CG Input follows, output is printed on file geo2.out
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
GEOBEGIN 0. 0. 0. 26. 0. 0.COMBINAT
geo2.out
Example 4:
* CG Input read from file BigHall.geo, output printed on file geo2.out
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+...
GEOBEGIN 0. 0. 25. 26. 0. 0.COMBINAT
BigHall.geo
geo2.out
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