Looking for plot data files

From: Patrick Rigney <patrick_at_evocative.com>
Date: Fri Aug 22 11:27:00 2003

> We have a couple of large format plotters in working order. One is an HP
> A3 plotter the other a very large Calcomp. I thought it would be nice to
> show these actually working and am searching for plot files of the
> classic pictures, for example the cut-away drawing of the space shuttle.
>
> Anyone know where such data files might be found?
>
> Regards,
>
> -- hbp

Hans, everyone has made great recommendations for file sources and various
methods of translation. I have an additional alternative you might want to
consider: writing your own driver program. I started my programming career
working for a company that made digital mapping software, and wrote many
plotter drivers (in Fortran IV even); they're generally pretty simple. HPGL
in particular is dead easy. In fact, if you just connect to the plotter
over the serial port using a comm program of some kind, you should be able
to type the commands on the list below (very incomplete) to make things
happen. With this information and a little more from web surfing, you can
pretty easily translate any vector format into HPGL:

SPn Select pen #n (on many you can SP0 to "unload" the pen carriage)
PD Put the pen down (on the paper)
PU Pick the pen up (off the paper)
PAx,y Plot absolute-move to x,y; pen moves to absolute coordinate
PRdx,dy Plot relative-move relative dx,dy from current position
IN Initialize the plotter (resets scaling, etc.; some use DF instead)
PG Eject the page (some models; roll feed may scroll)

You can separate commands with a semicolon or CR/LF. So
"IN;SP1;PU;PA1000,1000;PD;PR1000,0;PR0,1000;PR-1000,0;PR0,-1000;PU;PA0,0;PG"
will draw a box. If memory serves, the default units of the plotter are
1/1000" of an inch, so this sequence would draw a 1" square box about 1"
from the corner of the page. You need to watch out for page origin, which
varies from model to model, as do its paper handling characteristics (and
therefore its margins). Also be aware that some commands take longer to
execute than others (a long line takes longer to draw than a short one), so
your serial output should use handshaking if possible, may need to be slow
if not possible--blasting a long plot out at 9600 will surely overrun the
plotter and get you interesting results.

If you have a LaserJet printer around, many can print HPGL directly (great
for testing without burning up your pens). Just send ESC % 1 B (without
spaces between) before the HPGL data. Send ESC % 1 A to get out of HPGL
mode. I just tried on my LaserJet 4050, and it works fine.

This, of course, is much more work than other suggestions people have made,
but I myself am the sick sort that would consider this type of thing
"fun". --Patrick
Received on Fri Aug 22 2003 - 11:27:00 BST