sfpicks2rsf (2.0-git)
Creates a mask from horizons:

        sfpicks2rsf < in.rsf > out.rsf ntic=5 tmask=y extend=n above=n picks=

horizon format:

x1 h1
x2 h2
x3 h3
x4 h4
xn hn

xn> ... >x4 >x3 >x2>x1

picks (file) ascii file with two columns (x and h(x))
the x values must be increasing order,
you can easily achieve that by doing:

sort -k 1 unsorted_picks.txt > sorted_picks.txt

stdin 2D file from which the axes will be read
extend [false] Extends picks to the boundaries of the axis
n Do not extend
y Extend to boundary

tmask [true] write a mask (1 if z>h(x))
false put a tic on the horizon

above [false] put 1 above the horizon
true put 1 below the horizon

ntic [1] works with tmask=false; put 1 around ntic grid points
above and below the horizon.

stdout It writes a file with the same dimensions as stdin
with a mask function, 1 below the horizon 0 above

bool above=n [y/n]

bool extend=n [y/n]

int ntic=5

string picks=
parameters from input file
bool tmask=y [y/n]