SA-E3-2

SCIS & ISIS 2008

A Study for Virtual Scissors System under Thin
Haptic and Force Feedback Environment
Kenji Funahashi

Daisuke Kubotani

Yuji Iwahori

Koji Tanida

Nagoya Institute of Technology
Gokiso-cho, Showa-ku,
Nagoya, Japan
Email: kenji@nitech.ac.jp

Rinnai Corporation
2-26 Fukuzumi-cho,
Nakagawa-ku,
Nagoya, Japan

Chubu University
1200 Matsumoto-cho,Kasugai,
Aichi, Japan

Honda R&D Co., Ltd.
4630 Shimotakanezawa,
Haga-machi,
Tochigi, Japan

Abstract—This paper proposes the virtual scissors system using
virtual hands. Users can cut virtual paper with their own hands.
The purpose of this system is to make it easy to implement
different tools by only changing parameters in software. Other
purpose is to make system with small-scale input and output
devices for general applications, for example, only using thin
haptic information and force feedback. In this VR (Virtual
Reality) scissors system, various feedbacks were introduced inorder to cover any impressions such as the interference feelingfor interface problem while using the virtual scissors and cutting
the virtual paper. Using this system, users can manipulate andcut virtual scissors through a data-glove as similar to real ones.

I. I NTRODUCTION
Many researches on object manipulation in virtual spacehave been proposed. These virtual reality technologies arebeing applied to the medical area, space developments andamusement attractions, and these demands for the VR technology are getting higher. In this virtual object manipulation
technology field, there are many researches using glove type
input device [1]. The development of input device itself has
been advanced, the glove is marketed which has vibrators atfingertips to convey information and the glove which can makefeedback forces to each of four fingers and thumbs with wire.
On introducing haptic and force feedback, however, thesize of equipment probably will be large-scale and more
expensive. Of course in some field, i.e. medical field, priority isoften given to precision over cost, hence, for example, virtual
scissors system has been proposed in which the force feedback
is considered [2].
In this research, we considered the virtual scissors systemwith thin haptic and force feedback [3][4]. Especially, thesystem consists of only vibration feedback elements for smallscale size and low-price, because our goal is widely generalization. One of our proposals was that we considered vibrating
not only at the contact points but also at non-contact points,
and giving the cutting sound which is not calculated but a likesound effect. Other was that we gave an intentional feedback
delay on the system to make an operator have feeling likecutting a thick piece of paper.
In this paper, we describe firstly the outline of virtual
scissors system and next the informative control method. Thenwe would like to show the experiments and results. This

technique might be not only for virtual scissors system but
also for any virtual reality system to use at personal home.
II. V IRTUAL S CISSORS S YSTEM
A. Model of Scissors and Paper
In our system, we consider the scissors which moves, opens
and closes following the movement of the right hand (Figure1). For simplification, taking and releasing scissors are notconsidered. The scissors are always contacted with the thumb’s
first joint and forefinger’s first joint of the right hand. Then theContact point which blades contact each other as a working
point is calculated.
The virtual paper is defined as a plane, not curved, and ascollective vertices. And the lines connecting vertices together
are called Boundary. The newly-created lines by cutting operation are called Cut-line. Here the operator doesn’t execute
any operations except for closing blades, opening them andmoving while opening them, i.e., slide cutting as using knife
is not allowed, then the finite-size line of the collective Contact
points is defined as Cut-line after the operation of blade
closing. Hence separating paper is not considered in thisexperiment.
B. Interaction ModelIn this model, the blade parts of the scissors can interfere in
the paper at the Contact point, although the handle parts do notinterfere. At the same, the interference of virtual hand with thepaper is not considered. The cutting operation is executed only
as closing action by the operator, moving scissors as moving
action and opening blades as opening action. Then the pathof the contact point is generated. The path is calculated as the
Cut-line only when it is inside Boundary, although a path is
not generated if the scissors is closed with no contacts on thepaper.
III. F EEDBACK
A. Vibration
We give the operator some cutting feelings using vibratorsof data glove, although it is different from the strict force
feedback. On the glove, vibrators are set on the second andthird joint of each fingers and palm (Figure 2). First we haveto consider the strength and the position of vibrational stimuli.

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Fig. 1.

Model of scissors and paper

Three levels of the strength were we thought as below; 1) an
operator dose not feel it excessively, 2) can feel it, and 3) feelstrongly.
So where would be best position to vibrate? Of course weat the first thought it is the finger which contacts with scissors.
However cutting feeling by artificial vibration is already different from actual one, and vibrators are unfortunately set on thebackside of finger. We used our ingenuities to vibrate otherfingers which have no contacts with scissors and also palmin order to get quasi-feeling. And furthermore considering
simplification, the system was set to give a constant vibrationin action of cutting.
Fig. 2.

B. Cutting Sound
When cutting virtual paper, the system gives an operator
CG (Computer Graphics) image to observe the virtual world
visually. Using this system (probably many other systems), it
gives not only CG image but also cutting sound. The soundwas not computational, but recorded of the real sound of
cutting. When cutting operation, it decided the playback partas follows (Figure 3). The sound when the paper is cut was notconsidered for the thickness, the material of paper and also theshape, material and attitude of scissors, but considered for the
position of contact point of scissors’ blade. The playback partwas decided only by the contact point. The beginning point of
playback part is decided by the position of the contact point
for whole of the blade and the end point is decided by thecontact point when cutting operation ends in the same way.
So what kind of sound would be best? We tend to regard as
the same sound when using the same thickness paper of CG
image, the same shape scissors and the same size scissors of
CG image. However the system is already different at many
points. For example, the visual image in 2D Display is limited,the image is not so real, and haptic and force feedback is thin.
Then evaluation was done with some recorded sounds; somekinds of scissors and two materials as paper and cloth.
C. Intentional Delay
Heavy expression is sometimes introduced when execution
speed of PC is slow. As we drag a mouse cursor or an icon,

Vibrators on glove

Sound Data

begin
Fig. 3.

end

Playback part of cutting sound effectwe feel it heavy when its response is a little delayed. We madeexperimental design as a new method to make an operator feellike cutting a thick piece of paper with scissors in the virtual
space by an intentional feedback delay.
There are some related researches: one of them proposedthat making the motion of a mouse cursor on a monitor
faster/slower than the movement of bodily operation. The system was impressed as a hillclimb and a downhill respectively.
It gave an operator pseudo haptic [5].

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Fig. 4.

Delay and Pseudo haptic

Most of operator usually think high execution speed isbest. However we cut thick paper slowly, and can not cut
it fast because of the thickness. Our experimental system caninput the value of an operator’s hand motion and movement,
calculate the interaction to the virtual environment and display
the CG at 20 images per second. In other words, it contains
50ms delay resignedly. But we can feel that we manipulate byourselves. We generally can say that a virtual reality system isrealized when the delay is under 100ms. So we tried to makethe delay over 100ms (Figure 4).
IV. E XPERIMENT AND R ESULT
A. System Overview
The virtual scissors system mentioned above was implemented on a PC (Pentium4, 2.80GHz, 1GM memory) with C
language. The position of hand was detected by Polhemus
3SPACE FASTRAK and the angles of each finger weredetected by Immersion CyberTouch. The system appearance
and CG image of this system are shown in Figure 5 and 6.
It refreshed the CG image at 20 frames/sec. The virtual hand
shown in CG was assumed as that of adult man’s. And thelength of virtual scissors was given 190mm with 80mm blade.

Fig. 5.

System overview and Image

B. Vibration
In all experiments, the monitor was set up vertically andthe virtual paper was tilted as 45 degrees to the monitor.
The number of right-handed subjects was six and they had
10 minutes experience of this system before experiments. The
subject could draw forth the virtual paper by the left hand
movement.
In the first experiment, the strength and the position ofvibration (note that there were no cutting sound effects in thisexperiment) were evaluated. However, vibration at ring finger
and little finger did not give good results in pre-experiment.
And strong vibrations made feel bad. Hence we focused on
the thumb, fore and middle fingers and the palm at vibration
points, and set five patterns as follows;1) fingers: strength 2, palm: strength 2

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Fig. 6.

Execution screenTABLE I
REALITY FOR VIBRATION PART AND LEVEL

patternpoint (average)

1

4.22

2

5.27

3

5.00

4

3.61

5

3.16

2) fingers: strength 2, palm: strength 13) fingers: strength 2, palm: strength 34) fingers: strength 1, palm: strength 25) fingers: strength 3, palm: strength 2
where strength is;1) the subject dose not feel it excessively2) the subject can feel it3) no vibration
Every subject was tried three times for each pattern, thatis, they totally tried 15 times in randomized order. After eachtest, they answered its evaluation as level among 1 to 7 points.
The result of their averages is shown in TABLE I. The resultshows that a little vibration at palm was effective. Vibrations
at middle finger and the next forefinger were also effective,
where it was observed that these fingers sometimes contacted
to the outside of handle of scissors in the pre-experiment result.
C. Cutting Sound
In this experiment, we evaluate what kind of cutting soundwas effective, and whether the real sound was necessary also
in virtual scissors which was modeled with the real shape andmaterial.
We prepared some sheets of general paper (for printer) andsome pieces of cloth which was about 0.3mm of thickness,and seven kinds of scissors as follows;A) 45mm blade length, stainless steelB) 60mm blade length, stainless steelC) 75mm blade length, stainless steelD) 105mm blade length, stainless steelE) 140mm blade length, stainless steelF) 40mm blade length, stainless steel, the cut-line will be
zigzagG) 100mm blade length, steel, dressmaker’s shears, as sameas D in size and shape
These seven scissors are shown in Figure 7. Then we recorded
14 kinds of cutting sound, and we asked six subjects to evaluate the 14 kinds of cutting sound through VR system (notethat there were no vibration feedbacks in this experiment)
and the same 14 kinds of original real sound without VR
system. Each subject was listened to three times for each soundin randomized order. When a subject felt a sound good, theFig. 7.

Scissors A-G

subject pointed +1 to +3, when felt bad, pointed −1 to −3.
The result is shown in Figure 8.
In the result of this experiment, it is seen that scissors D and
E got higher points than A to C. The beginning position of
cutting sound is different from the end one, and the difference
became bigger when blades got longer. We could guess thatlong blades made subjects feel better. Although the blade
length of scissors G is the same as scissors D, it got lower
evaluation in the VR environment. We can guess the reason
is that some subjects felt cutting operation was light as seenin their comments because steel scissors made sound withhigh frequency. We think that an effective sound frequency
is necessary for the cutting operations.
D. Vibration and Sound EffectThen the effects of vibration feedback and cutting soundwere evaluated together. Following four conditions were prepared first;
1) only CG image
2) CG image and vibration feedback3) CG image and sound effect4) CG image and vibration and soundThe vibration pattern was set on the 3rd pattern and the cutting
sound was set with the D sound mentioned before. Next we

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TABLE II

point (average)

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Evaluation of cutting sound

REALITY UNDER EACH ENVIRONMENT

environment

E

D

C

B

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Fig. 8.

asked six subjects to evaluate these four conditions by 17 points. The result is shown in TABLE II. The vibration
heightened evaluation certainly, although the effect by vibration feedback was lower than sound effect.
E. Intentional Delay
Our system could be input motional values by the device
calculate the interaction and display the CG image and cutting
sound at 20 times per a second. It contained 50ms delay, but
we can generally judge it as real-time system under 100ms
delay in virtual reality field.
Here three conditions were prepared as follows;

1) no delay (50ms delay)
2) 200ms delay
3) 500ms delay
And the system gave the subjects feedbacks of CG image,vibration and cutting sound in each environment.
10 minutes after experience at condition 1, eight subjects
cut the virtual paper at each remaining condition. They triedeach condition in randomized order, and answered evaluations
as good/normal/bad and comments for them.
Two subjects evaluated condition 2 better than condition
1, and other two subjects answered the same evaluation for
condition 1 and condition 2 (TABLE III). We got comments
for every condition 2 experiments like;• It was heavy.
• Subject felt cutting thick paper.
• Scissors/paper is hard.
Four subjects evaluated condition 1 better than condition 2
according to their comments. As for condition 3, we got
comments like;• It was stressful.
• It was difficult to cut it straightly.
• Subject felt being old person.
Then we announced to them that the virtual paper was thicklike cardboard in fact, and asked them to try again and answer

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TABLE III

Many kinds of force and haptic feedback device have been
researched and developed, but the size and price of most ofthem are not for home use, while the vibrator system is used
for the silent mode of mobile phone and video game controller
recently. Although the data-glove we used is very expensive
one, there are/were some data-gloves for video game in themarket. It would be able to make a data-glove with vibrator ata low price in the future. Using this data-glove and the method
proposed, various virtual reality system might be produced andsold, for example, for our home through the internet.
Good results were obtained, but there are some points
to be improved. For example, we tested just some patternsof vibration position and strength level, cutting sound, anddelay time. As a future subject, these above problems areremained to be solved. Many patterns of them should betested and analyzed, and the optimized pattern should befound automatically. It also remains as our task that Touchable
Internet Shopping System should be realized.

EVALUATION FOR EACH DELAY

subject

environment 1

environment 2

environment 3

a

good

good

bad

b

good

normal

bad

c

good

normal

bad

d

good

normal

bad

e

good

normal

bad

f

good

good

bad

g

normal

good

bad

h

normalgoodbad

again. So all of evaluations of condition 2 turned good, andthe six of them was better than condition 1. From these results,
the minuteness delay of haptic information is effective as force
feedback. That is, time can be perceived as force.

ACKNOWLEDGMENT
Part of Iwahori’s research is supported by JSPS Grantin-Aid for Scientific Research (C) (20500168), Chubu Univ.
Grant and Nitto Foundation.

V. C ONCLUSION
Experimental evaluations were done using virtual scissors
system. The vibration feedback is effective as force feedback,and the vibrational stimulus where man can realistically nevertouch, i.e., palm is also effective. The cutting sound feedback
is effective on operational feeling, the sound which is replayedwith the real scissors is also effective even if the virtual
scissors size is different from real one.
The intentional delay is effective as force feedback too.
The appropriate delay of minuteness makes an operator feel
heavy and/or hard. Nevertheless our experiment after theannouncement that the virtual paper was thick showed thedelay was effective very much. Only delay is not so effective
and the delay is probably just supplementary. So, for example,
we have to use this method assuming thick paper of CG.

R EFERENCES[1] Kenji Funahashi, Takami Yasuda, Shigeki Yokoi and Jun-ichiro Toriwaki.
A Model for Manipulation of Objects with Virtual Hand in 3-D VirtualSpace, Systems and Computers in Japan, Vol.30, No.11, pp.22-32, 1999.
[2] A. M. Okamura, R. J. Webster III, J. T. Nolin, K. W. Johnson, and H.
Jafry. The Haptic Scissors: Cutting in Virtual Environments, Proc. the2003 IEEE International Conference on Robotics & Automation, pp.828833, 2003.
[3] Koji Tanida, Kenji Funahashi, Masao Ohmi, and Masashi Kusumi.
Embodiment Evaluation for Tools of Virtual Reality Technology -A
Trial Evaluation by Measuring Hemodynamic Change in the Brain-,Transactions of Virtual Reality Society of Japan, Vol.12, No.1, pp.3-10,
2007. (in Japanese)[4] Kenji Funahashi, Daisuke Kubotani, Koji Tanida, and Yuji Iwahori.
Pseudo Haptic Expression by Presentation Delay in Virtual Scissors System, Proc. the 12th Virtual Reality Society of Japan Annual Conference,
pp393-394, 2007. (in Japanese)[5] Anatole Lecuyer, Jean-Marie Burkhardt, Laurent Etienne. Feeling Bumps
and Holes without a Haptic Interface: the Perception of Pseudo-Haptic
Textures, Proc. ACM SIGCHI, 2004.

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