The code in the util_programs/photon_surface_plot directory is used for:
  1) Generating a data file of surface points for a Bmad lattice element.
  2) Generating a 3D plot of the surface using the data file and gnuplot.

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1) Generating the surface data

The program is photon_surface_data.f90.
This program is built with the standard Bmad Distribution.
To run use the syntax:
  photon_surface_data <init_file>
where <init_file> is the name of the initialization file containing the parameters needed by the
program to generate the data file.

An example input file is in example/photon_surface_data.init .
To run with this file, use the following command in the example directory:
  photon_surface_data photon_surface_data.init

This example input file is self documenting. look in this file for details.

The resulting data file looks like:

#     Ix      Iy          X                Y                Z              dZ/dX         dZ/dY
 
     -25     -10      -3.50987227E-02  -2.12821053E-02   2.66263866E-08 -1.728355E+00 -3.250801E+00
     -25      -9      -3.50987227E-02  -1.91538948E-02   1.21422273E-05 -1.728301E+00 -5.406615E+00
     -25      -8      -3.50987227E-02  -1.70256842E-02   4.84936425E-05 -1.728140E+00 -7.562425E+00
     -25      -7      -3.50987227E-02  -1.48974737E-02   1.09094709E-04 -1.727872E+00 -9.718226E+00
    ... etc ...

There are 7 columns.
The first two columns give indexes ix and iy.
The next three columns give the (x, y, z) point on the surface.
The final two columns give the surface slope with respect to x and y.

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2) Plotting the data.

There is a gnuplot command file named surface_plot.gp to draw in 3D either the surface or the surface slopes.

This command file looks for a data file named "surface.dat" so if your data file has a different name
you will need to edit surface_plot.gp.

To run, first start gnuplot and then use the command:
  gnuplot> load "<directory>/surface_plot.gp"
where <directory> is the directory that surface_plot.gp is in.
For example, when running from the example directory, you would use:
  gnuplot> load "../surface_plot.gp"

The default is to plot the surface z.
Note: Plotted is -z (not z) so that the view of the surface is from above (and not below).

To plot the slopes edit the file surface_plot.gp to use columns 6 or 7 instead of column 5.