3d scatter plot with splot: how to enable drop lines and grids on the vertical faces?

I used splot to get a  3d scatter plot in gnuplot. I have (x,y,z) triples 
that I wanted to plot as a 3d scatter plot. Something similar to what I 
post an image of here: 

http://picasaweb.google.com/rpnabar/DebugGnuplot3d?authkey=IUAWeyOtMGY

What's the best way to add the vertical drop lines to the xy plane? Also,
I 
could get gnuplot to draw the grid on the bottom but on the side faces it 
only draws the horizontal grid lines. How can I include the vertical lines

too?

I used:

set border 127+256+512 
set grid xtics ytics ztics
splot "data.txt" using 2:3:4 with points

Any sugesstions?

-- 
Rahul