8.2.1} GEOBEGIN card

 This card follows the general FLUKA format (see description in 6}).
 It can be in free format if the latter has been requested with
 option FREE. The rest of the geometry must be in a special fixed
 format described below, unless free geometry format has been requested
 by a GLOBAL command at the beginning of input.

 The meanings of the WHAT and 
SDUM
 parameters are:

     
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 factor NINT(
WHAT(1)
), expansion is
                      aborted and online parenthesis expansion is used.

     
WHAT(2)
        : absolute accuracy parameter (Aa) in units of 10**-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.
                      
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. Values of
                      
WHAT(4)
 /= 11.0 and < 21.0 must be avoided because
                      of possible conflicts with FLUKA pre-defined units.
                      
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)
        : not used

     
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

     
Default
 (option GEOBEGIN not given): not allowed! GEOBEGIN and
           GEOEND must always be present.

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