Try this as an example of the "smooth" program.  I'm assuming you've
downloaded and compiled "gforge" also.
----------

gforge -type mat -name hill.mat		         # generate a hill 
gforge -type pg8 -name flag.pgm -dim 2.5	 # generate flag mask file
smooth

  {type "hill.mat" as the input file, "50" for number of passes,
   and "hill1.mat" as the output file. }

hcon hill.mat hill.gif
hcon hill1.mat hill1.gif

---------- 
Now use your favorite GIF viewer to look at hill.gif and
hill1.gif to see what the effect of the smooth operation was.  Or, use hcon
to convert to a TGA and render in POV-Ray. (If you hadn't generated the
"flag.pgm" file, it would have all been smoothed.) Have fun!
