CROSS_SECTIONS Description:

   For a CFD surface dataset, structured or unstructured in three-space,
perform slicing at the indicated stations and process the slice data in
some way.  Common usage is expected to involve just one function, so no
provision was made for more than one originally.  EXCEPTION:  Slicing at
multiple azimuthal angles in a front view has been retrofitted, and there
it makes sense to allow any number of surface functions, all output along
slices in Tecplot form, as opposed to tabulating statistics for 1 function
at many X stations.  (Later: This version can now read Tecplot datasets as
well as PLOT3D datasets.  If the number of functions is greater than 1, the
original tabulation of max/min/mean data is simply not an option: slices
are output in Tecplot form only, at either X or angular stations.)

   The initial application is to surface heating data, where maxima and
minima and associated quantities are required at each of many stations.
Means and standard deviations are calculated via arc-length-based monotonic
spline quadrature.

   The slicing is implemented for X stations only, with an option to rotate
the surface coordinates as needed for such a simplifying approach.
EXCEPTION:  Slicing at angular stations assumes the slices are parallel to
the X axis with no rotation option to ensure this, at least initially.
Program ADJUST_GRID is available if necessary to satisfy this assumption.
The common origin of the angular slices need not be on the X axis.

   Two-point line segments are determined from triangular elements met by a
given slice plane, and all such segments from any one slice are organized
into 1 or more contiguous curves with no duplicate points (except possibly
the end points of a closed curve), as would be needed for line plotting
purposes - especially if more than one geometry component is represented by
the surface grid.

   The option for slicing at angular stations can handle both half & whole
bodies in a way appropriate to an axisymmetric blunt body.  E.g., "spokes"
of a half body all start with arc-length s = 0 at the origin of the slices
(if only one contiguous curve is present in each slice). Likewise, s starts
at 0 in a consistent way for the angular slices of a whole body (at either
one end or the other, depending on the ordering of the first slice, since
each slice after the first is arranged to start at the end nearest to the
start of the previous slice).

Control File (Standard Input):

   CROSS_SECTIONS Control File
   1          ! Analysis type:    1|2 = max/min/mean table|Tecplotable cuts
   1          ! Grid type:    1|2|3|4 = PLOT3D|PLOT3D/iblank|Tecplot|FUN3D
   3          ! Dimensions:       2|3 = 2D/(x,z)(inactive)|3D/(x,y,z)
   mygrid.gu  ! Grid file name | Tecplot or FUN3D dataset name
   F          ! Formatted?        T|F = ASCII|unformatted
   myflow.fu  ! Flow data file name if PLOT3D data
   F          ! Formatted?        T|F = ASCII|unformatted
   slices.dat ! Output file:      Tabulation|Tecplot slices
   X          ! slice coordinate: x|y|z|t; t[heta] => angular stations
   1000       ! Number of slices        (uniform for now)
   0. 0. 0.   ! Origin for clocking angle calculations or angular slices
   T          ! Merge subslices?  T|F = 1|1+ tabulation lines/slice

Output Table Format (some digits suppressed, with merging turned off):

# slice station      fmax    clock       fmin    clock       mean   st.dev.

   2  -11.1657  3.580E+04  -19.450  3.142E+04  -90.000  3.345E+04  1.37E+03
   2  -11.1657  4.072E+04   58.846  3.881E+04   17.308  4.035E+04  4.29E+02
   3  -11.1257  2.603E+04 -167.549  1.402E+04  -90.000  1.962E+04  3.76E+03
   3  -11.1257  3.228E+04   58.846  2.958E+04  164.087  3.182E+04  6.07E+02
   4  -11.0858  3.088E+04  124.365  5.343E+03 -103.596  2.282E+04  9.23E+03
   5  -11.0458  3.106E+04  136.212  3.523E+03  -90.000  2.571E+04  7.12E+03
   :     :       :            :      :            :      :          :

   [An extra arc length column is now included, with the option to merge
    subslices or not.  Merging is performed by storing subtotals that can
    be combined into single totals for the means and standard deviations.
    Mins. and maxs. are determined across all subslices.]

Output Tecplot Slices Format (analysis type 2, one zone per [sub]slice):

   TITLE = ""
   VARIABLES = "x"
   "y"
   "z"
   "s"
   "v1"
    :
   "vn"
   ZONE T="Theta=  0.0000"
   I=123, J=1, K=1, ZONETYPE=Ordered
   DATAPACKING=POINT
   1.234 0.000 0.000 0.000 5.678 9....
    :     :     :     :     :     :
   ZONE T="Theta=  1.0000"
   I=...
    :     :     :     :     :     :

   Actually, if there is more than one contiguous curve in a slice, that
   number of zones is output for that slice, all with the same zone title.

Origins:

      Todd White requested the initial capability to analyze a database of
   Launch Abort Vehicle flow solutions with TPS thickness in mind.  David
   Saunders had already written a couple of surface slicing applications
   employing quadrilateral/triangle utilities originated by Scott Thomas.
   The framework of the more recent SHADOWGRAPH program was considered
   more flexible than the earlier MULTICUT and MULTIPLOT.