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.TH GEN 1 "Ultrasonics Laboratory"
.SH NAME
gen - Generate Simulated Data for CT Scanners
.SH SYNOPSIS
gen [options...]
.SH DESCRIPTION
The program
.B gen
generates projection or flash data to be
used in testing reconstruction algorithms.
Data can be generated to simulate first,
second, third or fifth generation scanners.
.PP
The object to be scanned consists of up
to 10 superimposed ellipses.
An input file lists the parameters 
of each ellipse.
The data in the file consists
of a single line describing each
ellipse.
The data should be in ASCII and separated
by spaces.
Each line should contain 
(in order)
.TP .5i
1)
the x coordinate of the center of the ellipse,
.TP
2)
the y coordinate of the center of the ellipse,
.TP
3)
the angle between the major axis of the
ellipse and a horizontal line.
.TP
4)
the density (attenuation coefficient) of the ellipse.
Attenuations add when ellipses overlap.
.TP
5)
the length of the semi-major axis,
.TP
6) 
and the length of the semi-minor axis.
.PP
There are many variables and options that can
be used from the command line.
The variable are set by listing the name
of the variable, and equals sign and then
the new value of the data.
The data can be either a number or
a file name depending on the variable.
The variables and their default values are listed 
below.
.PP
.TP 13
r1=2
source radius
(the distance from the origin of the scanner to
the transmitter axis.)
.TP
r2=2
detector radius 
(the distance from the origin of the scanner to
the detector axis).
.TP
r=1
is the radius of the scan circle.
.TP
gamma=6
is half of the beam width of the fan.
.TP
n=10
is the number of detectors in the array.
The maximum number is 128.
.TP
k=1
is the number of projections.
.TP
m=10
is the number of ellipses in the 
object to be scanned.
Only the first 
.B m
ellipses are read from the input file.
The maximum number is 10.
.TP
nfl=100 
is the number of flashes in each translation
for fifth generation scanners.
.TP
ver=2
is the version of the generate routine to
use when calculating fifth generation data.
The default value is the latest version.
.TP
if=gen.d
is the file name that contains the data on
the ellipses.
.TP
of=for003.dat
is the output file name.
All of the calculated projection/flash data
will be in this file as single precision numbers.
.TP
rf=radon
is the file where radon space data will be output.
The file will contain pairs of single precision 
binary numbers. 
The first number will be the value of 'l' and
the second value is 'theta.'
See the
.B -r
option below.
.PP
There are several options that can be set from 
the command line .
They are (and the default value listed in parenthesis):
.TP 13
-1(on)
generate first generation data 
(single ray, linear translation, discrete rotation).
.TP
-2(off)
generate second generation data
(narrow beam, linear translation, discrete rotation).
.TP
-3(off)
generate third generation data
(wide beam, no translation, continuous rotation).
.TP
-5(off)
generate fifth generation data
(medium beam, some translation, continuous rotation).
.TP 
-a(off)
generate data for equal angular detectors.
This only applies to second, third and
fifth generation scanners.
.TP
-e(on)
generate data for equal spaced detectors.
This only applies to second, third and
fifth generation scanners.
.TP
-p(off)
don't print the program data.
.TP
-r(off)
save radon space data. 
Do not calculate projection/flash the
data.
See the 
.B rf=
parameter above for the output format.
.TP
-s(off)
sort flash data into projection data
for second, third and fifth generation scanners.
.TP
-d(off)
sort flash data into projection data
and delete end points in 
second and fifth generation scanners.
.TP
-w(off)
Use a weight function in fifth generation data.
.SH FILES
.TP 13
gen.d
is the default input file with the description
of the ellipses to be scanned.
.TP
for003.dat
is the default output data for the projection/flash data.
.TP
radon
is the file for vectors (l,theta) in radon space that
the scans cover.
.SH SEE ALSO
David Nahamoo, Carl R. Crawford and
Avinash C. Kak,
"Design Constraints and Reconstruction Algorithms
for Traverse-Continuous-Rotate Scanners,"
IEEE Transaction on Biomedical Engineering,
Vol BME-28, November 1981,
pp 79-98.
.SH DIAGNOSTICS
Error messages are printed if files can not be opened,
if any of the parameters are out of bounds
or if the ellipse data is not correct.