NAME

genphot - generate test rays


SYNOPSIS

genphot parameters


DESCRIPTION

genphot generates parallel rays from two dimensional geometric sources oriented in the X-Y plane. The rays share an arbitrary direction vector. The rays are written in bpipe format.

The shape of the filled area is specified with the geo parameter. The center of the area is specified by x and y; the area may be rotated, with rotation angle specified by phi.

The area may be filled with a grid of rays, or randomly (uniformly) filled. This is specified with the dist parameter. If random filling is used, the seed1, seed2, and block parameters must be specified. If grid filling is used, the nx and ny parameters must be specified.

The energy distribution of the rays may be specified with the spectrum parameter. The bins must not overlap, all values of counts must be non-negative, and the minimum energy for a bin must always be less than the maximum energy. If spectrum is set to ``none'' or omitted, the energy of the ray is specified by the energy keyword. The way that the spectrum is sampled is specified by the energy_dist parameter. Note that several of the options for the latter will override the photdens parameter.


ARGUMENTS

genphot uses an IRAF-compatible parameter interface.

output

The destination for the output rays. If it is the string stdout, it writes to the standard output stream. It writes bpipe formatted rays.

geo

The geometric form that the rays may fill. See OUTPUT SHAPES for more information.

dist

The ray pattern used to fill the geometric area. It is one of uniform, grid.

See RAY DISTRIBUTION for more information.

photdens

The parameter regulates the number of rays output. For points, it is the number of rays. For one dimensional shapes, it is the number of rays/mm. For two dimensional shapes it is the number of rays/mm^2.

If the ray distribution (dist) is grid, it is ignored.

seed1

The first random number seed. It can range from 1 to 2147483562, inclusive. used only if dist is uniform.

seed2

The second random number seed. It can range from 1 to 2147483398, inclusive. used only if dist is uniform.

block

The starting block in the random number stream. It can range from 0 to 1048575, inclusive. used only if dist is uniform.

x

The X coordinate of the center of the field to fill.

y

The Y coordinate of the center of the field to fill.

z

The Z coordinate of the rays.

phi

The rotation angle of the field, in degrees.

ray_theta

The spherical coordinate elevation angle of photon direction in degrees

ray_phi

The spherical coordinate azimuthal angle of photon direction in degrees

height

The height of the rectangle. Used only if geo is rect-peri or rect-fill.

width

The width of the rectangle. Used only if geo is rect-peri or rect-fill.

maj

The major axis of the ellipse. Used only if geo is ellipse-fill.

min

The minor axis of the ellipse. Used only if geo is ellipse-fill.

radius

The radius of the circle. Used only if geo is circ-peri.

ri

The inner radius of the annulus. Used only if geo is annulus-fill.

ro

The outer radius of the annulus. Used only if geo is annulus-fill.

nx

The number of grid sites in the X direction. Used only if dist is grid.

ny

The number of grid sites in the Y direction. Used only if dist is grid.

spectrum

A file containing the energy spectrum to sample, in RDB format. If it is stdin, the spectrum is read from the standard input stream.

The columns are emin (the minimum energy in the bin), emax (the maximum energy in the bin), and counts (the number of counts within the bin). If the spectrum is either not specified or is specified as none, the energy will be read from the parameter file.

energy_dist

How the spectrum specified by the spectrum keyword is sampled. It may be one of:

sample

Sample the spectrum according to the relative probability of the input bins. After a bin is selected, an energy is uniformly sampled from within the bin's limits.

picket

Sample the spectrum according to the relative probability of the input bins. The output energies are the minimum energies of the bins.

min

The energies will be the minimum energies of the bins. This option also limits the number of photons output to be equal to the number of bins. It thus overrides the photdens parameter. The only column required in the RDB table is emin.

max

The energies will be the maximum energies of the bins. This option also limits the number of photons output to be equal to the number of bins. It thus overrides the photdens parameter. The only column required in the RDB table is emin.

ave

The energies will be the averages of the bin limits. This option also limits the number of photons output to be equal to the number of bins. It thus overrides the photdens parameter. The only columns required in the RDB table are emin and emax.

energy

the energy to assign to the ray. used only if spectrum is ``none'' or not specified.

debug

A list of debug flags. None are presently defined.

help

Print some documentation and exit.

version

Print the version and exit.


OUTPUT SHAPES

genphot can fill a variety of output shapes. This is controlled by the geo parameter, which can have the following values:

rect-peri

The perimeter of a rectangle. See the height and width parameters.

p=item rect-fill

A filled rectangle. See the height and width parameters.

ellipse-fill

A filled ellipse. See the maj and min parameters.

circ-peri

The perimeter of a circle. See the radius parameter.

annulus-fill

A filled annulus. See the ri and ro parameters.

point

A point. In this case, the photdens parameter specifies the number of photons to generate.


RAY DISTRIBUTION

How the rays fill the desired output shape is controlled by the dist parameter.

It can have one of the following values:

uniform

Fill the space uniformly (randomly).

grid

Place rays on a grid. The nx and ny parameters control the grid spacing within the smallest rectangle which encloses the output shape. The actual number of rays output depends upon how much of the rectangular grid is within the output shape.


COPYRIGHT & LICENSE

Copyright 2006 Smithsonian Astrophysical Observatory

This software is released under the GNU General Public License. You may find a copy at

          http://www.fsf.org/copyleft/gpl.html


VERSION

This documents version 1.1.2 of genphot.


AUTHORS

Diab Jerius <djerius@cfa.harvard.edu>

Ivan Stern

David Grumm