schnable@ihuxf.UUCP (06/29/83)
Hal, While both a light pen and a mouse can be used to point at things, there are differences. A mouse has a much finer pointing resolution than a light pen (at least the light pens that I have used). If you are trying to draw something on the screen or to edit graphics (icons and the like), this can be very important. The light pen's pointing end is just too big and bulky, and it can obscure the view of what you are working on. Also, the mouse movements can be tracked. This allows you to sweep out areas and to rubber band lines. I have not seen this done with light pens. The mouse buttons are designed to fit naturally under the fingers when the mouse is held. Where would you put buttons on a light pen that did not interfere with tracking or with comfortable holding? On the other hand, pointing right at the screen does have certain advantages. It is more natural. But why use a light pen? Why not just use a touch sensitive screen and your finger? About a year ago I saw a comparison of various pointing devices in some fa.* gateway group. If anyone has a copy of this maybe they should post it. Does anyone have any references for a comparison of rats, pads, pens, balls, sticks and screens? (5 points: what have I missed?) Happy with my rodent, Andy Schnable IH BTL x2680 ihuxf!schnable
brucec@orca.UUCP (06/29/83)
The classic paper on evaluation of computer input devices is "Evaluation of Mouse, Rate-Controlled Isometric Joystick, Step Keys, and Text Keys for Text Selection on a CRT" Card, et. al., Xerox Technical Report SSL-77-1, Xerox Palo Alto Research Center, 1977. The paper compares the devices for speed and error rate in selecting characters, and derives some equations from the data in an attempt to find a basis in control theory for the results. At this time there is a rather large body of research on various aspects of manual control, much of it stimulated by the military or the space program. Unfortunately, it's a relatively esoteric study as far as most engineers or computer scientists are concerned (neither ACM SIGCHI, nor IEEE Systems, Man, and Cybernetics society is large). So there aren't a lot of people who know that there is prior art when they design an interactive computer system. I hope that this will change as the emphasis on human interface technology increases. Bruce Cohen UUCP: ...!teklabs!tekecs!brucec CSNET: tekecs!brucec@tektronix ARPA: tekecs!brucec.tektronix@rand-relay
grunwald@uiuccsb.UUCP (06/30/83)
#R:sri-arpa:-253800:uiuccsb:4400002:000:311 uiuccsb!grunwald Jun 29 17:11:00 1983 I find a light pen as difficult to use as a mouse, if not more. Additionally, various experiments have shown that a mouse is faster and less error prone than a light pen for pointing to a specific spot on the screen (this is from a rather famous reference on the subject -- I'll send it to you if you wish).
msc@qubix.UUCP (06/30/83)
The question of what kind of pointing device to use is very much
a religous issue just like the choice of editor. Nevertheless here
is my 2 pence worth.
My problem with light pens and their ilk (e.g. sonic digitizers)
is that I have to reach out for the screen. Thus I cannot
sit back and relax at my work as I can with a mouse.
I would agree that a light pen is a more obvious pointing device
than a mouse. However, if you look at modern user interfaces
such as Smalltalk, Lisa, and VisiOn you will see that there is a lot
more than just pointing going on. Look, for example, at the action
required for selecting from a draw down menu on the Lisa. Or look at
the action required to move or re-size a window.
--
Mark
...{decvax,ucbvax}!decwrl!qubix!msc
...{ittvax,amd70}!qubix!msc
decwrl!qubix!msc@Berkeley.ARPAleichter@yale-com.UUCP (06/30/83)
About light pens: First, the good news. The large radius of the pen tip does NOT make accurate pointing impossible; you can be clever. What you do is project a crosshair pattern just above where the pen is sensed to be. Other than the pen-control software, everyone thinks the pen is "at" wherever the CROSS-HAIR is; it can be controlled quite accurately. (This isn't my idea, BTW, but I'm afraid I don't have the reference...) Now, the bad news: Light pens have one really unfortunate feature: You have to hold them up to a vertical display screen. This is very tiring after a fairly short time, as many experiments have shown. That's the main reason light pens haven't been that heavily used. (Of course, if you build the screen into your desktop, you have a different situation...) The single best "pointing device" I've ever heard of was developed at Bell Labs a couple of years back - again, sorry, I don't have the reference. The system was called something like "reading through your hand". You used a half-silvered mirror to project a "semi-transparent" image of your hand over an image of the screen. It turns out that, if you do it right, the image doesn't interfere at all with your ability to read what is on the screen, but provides you with all the feedback you need to control your hand. The position of the hand is, of course, read by some sort of touch-sensitive surface. This hasn't caught on, probably because the size, complexity, and cost of the necessary equipment. -- Jerry decvax!yale-comix!leichter leichter@yale
brucec@orca.UUCP (07/01/83)
I generally agree with the comments about light pens, that they are clumsy and fatiguing. Mice and tablets seem to be the best devices around, both from my own experience and that of others whom I respect (if you don't agree with me I don't guarantee to respect you (:-) ). I've heard of the Bell Labs gadget that jerry@yale-comix describes, but as I recall it had two problems: high cost, and a half-silvered mirror that could not be kept clean enough in an operational environment. Granted that touch panel devices on the market today are mighty crude, there is still a lot that can be done with them. An experimental device developed at MIT a few years ago could get pressure and pressure vector information at high resolution from a finger touch. There is a paper about it in Computer Graphics, Vol. 12, No.3. It was possible to push a cursor around, and even rotate it properly, by holding a finger against the screen at one point and pushing obliqely. This is nice for human interface, because the kinesthetic sense gets much more precise feedback from force than it does from position (I can't give a precise reference here, but there were studies by the Air Force which resulted in the two-regime control stick for the F-4). My vote for the absolute best pointing device interface goes to the "Put That There" system implemented on the Media Room facility at the MIT Architecture Machine Group (see articles by Richard Bolt in the SIGGRAPH '80 and '81 proceedings, Computer Graphics Volume 14, No. 3 and Vol. 15, No. 3). Here the operator sits in a comfortable, high backed lounge chair in front of a large rear-projection color video screen. To point to something, he literally points his finger (an electromagnetic field generated by a box on his wrist is detected by a fixed receiver) and speaks a command. No buttons, no styli, no muss, no fuss. By the way, I do not now, and never have had any connection with MIT. It's just that in the late '70s and early '80s they did a lot of fascinating work on human-machine interaction. MIT people correct me if I am wrong, but I get the impression that a lot of it was at the instigation, or with the assistance of, Nicholas Negroponte, who is one of the US scientists recruited by the French government for their Informatique project. Bruce Cohen UUCP: ...!teklabs!tekecs!brucec CSNET: tekecs!brucec@tektronix ARPA: tekecs!brucec.tektronix@rand-relay
ravi@hcr.UUCP (Ravi Pandya) (07/04/83)
Yes, there was some very fascinating interaction work done at MIT, and all
the really interesting stuff that I've heard of was done by Nicholas
Negroponte's Architecture Machine Group (I have heard that he is no longer
in France, but is still on leave from MIT). Their goal was (and is) to
develop a machine that can actively help an architect in the design process;
it is like expert systems, but with a fresh twist -- Negroponte felt that
in order to truly understand the design process and its goals, the
Architecture Machine would have to interact with people in as many ways as
a person interacts with his environment, so he did all kinds of interesting
things with touch panels, eye trackers, pointing trackers, wall-size
screens, and the like. He published a lot of papers about it, many in
architectural magazines, and a couple of books (published by MIT Press, of
course: "The Architecture Machine" and "Soft Architecture Machines").
If anyone from the Architecture Machine Group is on the net, I'd be really
interested in hearing what you are doing now, and what kind of things
you have in the works. Thanks.
--ravi
{linus,floyd,allegra,ihnp4}!utzoo!hcr!hcrvax!ravismh@mit-eddie.UUCP (07/04/83)
A more complete explication of the `crosshair' method for following a lightpen, cited a while ago by Jerry Leichter: The solution involves displaying a right-angle cross comfortably larger than the aperture of the pen. The cross point displays the cursor position. Following consists of keeping track how far from the cross point in opposite directions the cross is visible to the detector. The tracking algorithm continually adjusts its idea of the cursor location to keep the visible portion of the cross centered. That's all in theory, for there are several practical problems. For some applications, it is necessary to have an acquisition mode in which the display fills the screen with hash in order to pick up the initial position of the pen. (Otherwise, the user must point to the displayed cursor to `pick it up,' analagous to picking up a mouse.) Some sort of smoothing algorithm is necessary on tracking, for detection at the extremes of the aperture tends to be noisy (or rather, statistical). All this, of course, burns a lot of processor time (possibly all of it), although the problem can be moved to a dedicated microprocessor. Remember, a mouse generates no output while stationary. Also, this technique awkward to implement on some lightpen/display hardware. My experience (which is admittedly ancient) is that lightpens work a lot better for pointing to discrete objects, such as menus, than they do for detailed tracing. Like Jerry I cannot provide a reference for first use of the crosshair method. However, it was the common penfollow technique used at the MIT RLE PDP1 in the mid '60s. (If my sources are any good, this this machine with its old point-plotting display, but without the exotic timesharing hardware, is now on display and running at the DEC museum in Marlborough MA.) Steve Haflich genrad!mit-eddie!smh
newman@utcsrgv.UUCP (Ken Newman) (07/04/83)
The only problem with putting a crt into a desktop is that you would VERY quickly get a sore neck looking at the damn thing. Ever played those table-top video games for a while? Or written say 10 pages longhand on paper at a desk in one sitting? Seems that the light pen was yet another silly idea.
wdr@security.UUCP (William D Ricker) (07/06/83)
It has been documented by the Human Factors study people {referneces
from Ben Schneiderman's talk to GBC/ACM/PDS} that light pens cause more
fatigue due to lifting of the arms. Experienced Users of both will
generally prefer pointing and mouse devices not located on the screen.
Bill Ricker
(617)271-3725 MS k203, The MITRE Corporation, Bedford, MA, 01730
wdr@security.UUCP (Internet)
{allegra,genrad,ihnp4,utzoo,philabs,uw-beaver}!linus!security!wdr (UUCP)
wdr@mitre-bedford (ARPA)dave@rocksvax.UUCP (07/07/83)
Having used mice now for a number of years on our internal Alto computers I have to say a mouse is a winner. I don't know about you but the thought of holding my arm at head level rather than on a table surface makes my arm ache. The point about multiple buttons on the mice verses the light pen is a good one, mice should have at least 3 buttons. This allows you to do all sorts of "pointing commands": selects/delete/moves/etc. The trackballs have too much inertia when going large distances and you end up overshooting. Light pens need a "light" icon to point at something, unless you allow some background "grey" to exist on the CRT. Think about pointing at the end of a line with a light pen, there are no characters there to get a signal from. Dave
earl%brl-vld@sri-unix.UUCP (07/08/83)
From: Earl Weaver (VLD/VMB) <earl@brl-vld> It seems that the most widespread drawback with light pens is the grueling effort it takes to use them. However, it also seems that that impression is often promulgated by non-light pen users. Now I personally don't care much for light pens, but I know of an interesting situation where a BIG user of graphics had to decide whether or not to switch to data tablets instead of light pens. The company (McDonnell Douglas in St. Louis) had been using the IBM 2250s and 3250s and wanted to upgrade and decided on E & S hardware. BUT, E & S did not offer light pens at the time for that hardware. The users took a vote and said that they WANTED light pens--not tablets. As a result, E & S developed light pens for that hardware. That was a couple of years ago, but I suspect McDD people still prefer the light pens. I think the subject is almost like discussing one's favorite color.... -Earl
guy@rlgvax.UUCP (07/09/83)
I had heard that Xerox picked a two-button mouse for the Star because they
felt that three buttons were too many; the reason was that the buttons all
had different meanings in different programs. Was that the reason, and
is there a reason why three-button mouses necessarily lead to this? One
reason the Alto may have had this problem is that the Alto software wasn't
all part of one big project (people who have stumbled across the same UNIX
command flag character meaning one thing in one program and another thing
in another may recognize this problem), but was written as separate projects.
Or was the reason that they couldn't think of three uses for the three buttons
that could mean the same thing across all applications?
Guy Harris
{seismo,mcnc,we13,brl-bmd,allegra}!rlgvax!guysmh@mit-eddie.UUCP (07/10/83)
The question is why lightpens are not more used, as pointing to the screen seems more natural. Alas, it really isn't. Tape a piece of paper to your present CRT screen and try writing on it. Try the same thing on a piece of paper placed normally on your desk. The point is that it is very awkward writing or doing detailed pointing with your arm suspended in midair. (It can also be very tiring, as we academic types who do a lot of blackboard work can attest.) Lastly, performing a quick point takes far longer as the pen must be located, picked up, used, and put down again. A mouse is usually already sitting on its working surface when you want it. Perhaps these problems with lightpens could be fixed if someone would make a CRT with a tube built into a desk top (plexiglass cover, etc.)... The end device would have zero footprint when it wasn't being used! Steve Haflich genrad!mit-eddie!smh
MDP@SU-SCORE.ARPA (07/11/83)
From: Mike Peeler <MDP@SU-SCORE.ARPA>
Earl,
Yes, heavy light pen users might develop a preference
for them. After all, artists do not complain about having
to lift the brush to a vertically-mounted canvas all day.
On the flip side, Bulgarian farmers do not complain about
not having tractors, either. Personally, I prefer the
tracking device which rests on the table--the mouse.
Cheers,
Mike
-------MCMANIS%usc-eclc@sri-unix.UUCP (07/12/83)
From: Chuck McManis <MCMANIS@usc-eclc>
Xerox seems to changed the three independent mouse button into a pair
with three combonations. ("left", "right", and "chord") this still
gives them three modes but only two buttons, this in contrast to the
7 combonations (all off is not a combonation in this case) on the alto
which were rarely used because no one seemed to want to remember more than
three.
--Chuck
-------CSvax:Pucc-H:Physics:hal@pur-ee.UUCP (07/20/83)
#R:sri-arpa:-253800:pur-phy:7800005:000:452
pur-phy!hal Jun 28 11:36:00 1983
It seems to me that a light pen will do everything a mouse will and is
a much more direct pointing instrument. Admittedly, a light pen isn't going
to handle 3 buttons (2 is probably the maximum) but that is a matter of much
debate anyhow and doesn't directly relate to a mouse/light-pen choice. Many
of the video display chips support light pen hardware. I really don't know
why it isn't used more.
Hal Chambers
Physics Dept.
Purdue University