THE EFFECT OF HAPTIC GUIDES ON HUMAN PERFORMANCE

IN VIRTUAL ENVIRONMENTS

Sehat Ullah

, Samir Otmane

, Paul Richard

and Malik Mallem

IBISC Laboratory, University of Evry/CNRS FRE 3190, 40 rue ,du Pelvoux 91000 Evry, France

LISA Laboratory University of Angers, 62 avenue N.-D. du Lac 49000 Angers, France

Keywords:

Virtual reality, Human-scale, 3D Interaction techniques, Haptic guide, Human performance.

Abstract:

In order to make the virtual environments(VE’s) more realistic and to increase human performance, the inclu-

sion of haptic modality becomes more important. In this paper we present two new haptic guides. The haptic

guides are fundamentally aimed to assist users for object selection in VE’s. We divide the virtual environ-

ment into three zones. In the ﬁrst zone the user can freely move and don’t use any sort of guides. In the 2nd

zone, user is given visual guidance and the 3rd zone contains haptic guides along with visual guides. As the

paper presents two different models of the haptic guides, one for free and multidirectional selection and the

second for precise and single direction selection. We not only study the effect of these guides on human task

performance in the VE but also investigate a comparison of the two haptic models.

1 INTRODUCTION

From the very ﬁrst day of virtual reality, researchers

have investigated, proposed and evaluated various in-

teraction techniques including those trying to solve

the problem of grabbing and manipulating of ob-

jects (Bowman, 1999), (Pierce et al., 1997), (Stoakley

et al., 1995). Selection/grabbing is the fundamental

step which is taken before manipulating an object or

usually command control in VE. On the other hand,

user is also required to reach or approach the object

he/she intends to select, therefore need free movement

in the VE. This we model and implement in the form

of a ”free zone” in the VE, also discussed in (Ouram-

dane et al., 2006). The second zone we propose con-

tains a visual guide (Otmane et al., 2000b) which is

dynamically activated to guide the user for object’s

selection.

The third zone that we propose contains haptic guides

which actively assist the user towards the object and

makes the selection easier. Furthermore we imple-

ment two different versions of the haptic guide; one

is supposed to act from all directions around the ob-

ject and can be effectively used in applications that

do not necessitate a speciﬁc point or direction in se-

lection. The second acts in a single direction which

is pre-speciﬁed as object’s selection direction, obvi-

ously it can be used in applications where objects are

selected or grabbed from a speciﬁc point, for example

objects selection or grabbing by robots. This section

is followed by the related work, section 3 presents the

proposed haptic guide and hardware/software setup.

Section 4 describes experiments and evaluation. Con-

clusion is given in section 5.

2 RELATED WORK

A lot of work related has already been done in VR

systems, Bowman (Bowman, 1999) has carried out a

detail taxonomy of object selection and manipulation

based on task decomposition. Similarly (Poupyrev

et al., 1998), (Poupyrev and Ichikawa, 1999) have par-

titioned the interaction into two broad categories: ex-

ocentric interactions and egocentric interactions. In

exocentric interactions users interact with VEs from

the outside (also known as the God’s eye viewpoint).

The World-In-Miniature (Stoakley et al., 1995) and

automatic scaling (Mine et al., 1997) are examples of

exocentric type interaction. In egocentric interaction,

the user interacts from inside the environment. The

egocentric interactions are further divided into two

metaphors: virtual pointer and virtual hand. The vir-

tual pointer uses a vector for object selection and ma-

nipulation (Pierce et al., 1997). similarly we may re-

fer to the Ray-Casting technique (Mine et al., 1997),

uses a laser pointer - an inﬁnite ray extending from

the virtual pointer. The ﬂash light technique (Liang

322

Ullah S., Otmane S., Richard P. and Mallem M.

THE EFFECT OF HAPTIC GUIDES ON HUMAN PERFORMANCE IN VIRTUAL ENVIRONMENTS.

DOI: 10.5220/0001799003220327

In Proceedings of the Fourth International Conference on Computer Graphics Theory and Applications (VISIGRAPP 2009), page

ISBN: 978-989-8111-67-8

and Green, 1994) use the same principle as the Ray-

casting technique, but the laser pointer is replaced by

an inﬁnite cone. In the case of virtual hand metaphors,

virtual representation of the real hand is used. Here,

an object in the VE can be selected and/or manipu-

lated when the virtual hand touches the object (Stur-

man et al., 1989),(Poupyrev et al., 1996). The PRISM

(Frees and Kessler, 2005) technique is used as an ad-

dition to other existing techniques to increase preci-

sion.

In order to make the interaction easier and increase

user performance, various aides like stereoscopic dis-

play, 3D audio or haptic feedback may be exploited.

In the context of assistance for 3D interaction, virtual

guides (Rosenberg, 1993) are valuable tools, for ex-

ample in the context of teleoperation (Otmane et al.,

2000b). The haptic virtual Fixtures (virtual Fixture),

currently being used mainly in robot-assisted manipu-

lation tasks, are simply software-generated forces and

position signals that guide the user along a speciﬁed

path and/or prevent penetration into forbidden regions

(Abbott et al., 2005). In these type of haptic vir-

tual ﬁxtures users not only have very little freedom

but also lack visual guides that may reduce perfor-

mance. Similarly (Ren et al., 2007) has proposed

haptically augmented surgical system limiting the sur-

geon movement in certain areas. Oakley et al. have

investigated the use of haptic feedback in GUI’s and

have concluded that carefully designed force feed-

back may bring best performance (Oakley et al., 2002

). Alex B. (Alex B. et al., 2004) have used virtual ﬁx-

tures for targeting tasks in a desktop environment, but

these can only be used with static objects with prede-

ﬁned path. Similarly they superimpose the visual and

haptic ﬁxtures on each other.

3 PROPOSED SYSTEM

3.1 Proposed Models for Haptic Guides

Concerning the spherical guide, all objects in the VE

share the same ”free manipulation zone”. Further-

more each object in VE is separately surrounded by

two concentric spherical zones, having different radii.

The outer sphere acts as a visual zone and is acti-

vated (becomes visible) when the condition D

≤ R

becomes true and remains active till the object is

selected for manipulation. Here D

represents the

distance between the virtual pointer and the object

whereas R

is the radius of the visual sphere. Simi-

larly haptic guide activates itself when the condition

≤ R

is true, where R

is the radius of the haptic

sphere (not visible). Once haptic guide is active, the

user feels an attractive force towards the object. The

haptic guide is deactivated when the above mentioned

condition becomes false or the object is selected for

manipulation. The magnitude F of the attractive force

is calculated according to the following equation.

F = K +

t+1

−V

)

(1)

Here K > 0 is a constant which not only signify the

minimum attractive force felt by the user but also

gives a sense of transition between the spheres, it is

always present as long as the user is inside the hap-

tic sphere. Care should be taken in determining R

in order to avoid the overlapping of haptic sphere of

two objects if they are close to each other. The force

calculating mechanism is very interesting in the sense

that we keep count of the user’s change of velocity

i.e. if his/her velocity V

t+1

is greater than that of V

, the attractive force increases as a consequence and

vice versa. Referring to (Abbott et al., 2005) vir-

tual ﬁxtures (haptic guides), are used to provide either

assistance to the users or prevent them entering into

forbidden regions. Furthermore they can be either

of impedance or admittance type. Here the attractive

force in our haptic model provides assistance to user

in object’s selection. Similarly this may be called an

amalgamation of both impedance and admittance type

guidance because of the minimum force of magnitude

K is always present inside the haptic sphere, and in-

crease and/or decrease in it depends on user’s velocity

towards the object. The spherical guide is illustrated

in ﬁgure 1.

Figure 1: Illustration of the spherical guide.

Like the spherical implementation here the ”free ma-

nipulation zone” is common to all objects but the in-

ner two zones (visual and haptic) are implemented

using cones, in order to conﬁne users to select ob-

jects from a single and speciﬁc direction. The virtual

pointer always emanates a laser ray in the direction of

THE EFFECT OF HAPTIC GUIDES ON HUMAN PERFORMANCE IN VIRTUAL ENVIRONMENTS

323

selection. The visual guide is activated over the near-

est object in virtual world through which not only the

laser ray passes but the condition D

≤ L

also be-

comes true. Here D

is distance between the virtual

pointer and object, L

is the length of visual cone.

In the active visual guide (cone), if the user further

moves towards the object the haptic guide is activated

when D

≤ L

occurs, where L

is the length of the

haptic cone. The attractive force is calculated as fol-

lows:

F =

1 + D

t+1

−V

)

(2)

Here again K > 0 is constant signifying the minimum

attractive force and acts as a transition signal between

the two zones. In this model the resultant force is

dependent on two factor, ﬁrst is D

which is the dis-

tance between the pointer and axis passing through

the center of the cone, and second is the user’s change

in velocity towards object. Therefore this haptic guide

combines the characteristics of both guidance virtual

ﬁxtures and ”forbidden region virtual ﬁxtures”. Gran-

ularity is an important concept associated with inter-

action in VE, and maps the relationship between the

user’s movements in the real world with those of the

virtual world (Ouramdane et al., 2006). For exam-

ple, mapping large movements (in real the world) of

the user into small ones (in the VE) and vice versa,

or some loss in the degree of freedom etc. may cre-

ate some difﬁculties for the user at cognitive level, for

example, when he/she can freely move the real world

pointer in all directions but the corresponding virtual

pointer is restricted to move in a single direction. In

our solution, once the user is inside the haptic cone,

his/her movements are not only restricted in the vir-

tual world but also in the physical world, through our

force feedback device SPIDAR (Space Interface De-

vice for Artiﬁcial Reality) (Sato, 2002), (Tarrin et al.,

2003), (Richard et al., 2006), thus providing more re-

alistic interactions. The conical guide is illustrated

ﬁgure 2

Figure 2: Illustration of the conical guide.

3.2 Platform Setup

For experimentation we use a large scale semi-

immersive environment equipped with a retro-

projected large screen (3m x 2.5m) for stereoscopic

images, viewed with polarized glasses. We used hu-

man scale (3m x 3m x 3m ) SPIDAR , placed in front

of large display screen. The motors, encoders and

pulleys are mounted on the corners of the iron cubic

frame as shown in the ﬁgure 3. The High Deﬁnition

Haptic Controller (HDHC) takes encoders’ counts to

calculate grip’s position and orientation, provides ten-

sion to the strings to simulate force and communicate

with computer via USB 2.0. Because it is a string-

based system, so it is transparent, safe and simple.

Figure 3: Illustrations of SPIDAR (a) Motors and strings

(b) HDHC (c) Computer.

3.3 Software Architecture

The software we used to implement the haptic guides

in VE has client-server(installed on two different ma-

chines) architecture as illustrated in the ﬁgure 4

Figure 4: Illustration of the software architecture.

We developed the server part of this software using

C++ language. This part of the software performs the

following tasks:

1. Establish PC and HDHC controller communica-

tion 2. Take the calculated position and orientation

from the HDHC controller. 3. Establish connection

GRAPP 2009 - International Conference on Computer Graphics Theory and Applications

324

with Virtools client. 4. Calculate and display forces

or weight based on the information received from the

client

The client part of this software was developed using

Virtools Dev4.0 environment. This part is responsible

for the presentation of VE and supports the interac-

tivity between the virtual objects and the user. The

position and orientation sent by the SPIDAR server

are applied to the virtual pointer. The information

collected and sent by the client to the server includes

current zone of the virtual pointer, activation and de-

activation events for haptic zone, radius or length of

the haptic zone, distance between the virtual pointer

and the object, information on collision detection and

force direction etc.

4 EXPERIMENTS

4.1 Experimental Protocol

In order to investigate the effect of the proposed

haptic guides on human performance, 20 volunteers

males subjects participated in the experiments. They

were all master, PhD or post doc students having age

from 23 to 35 years. All of them were right handed

and had prior knowledge of interactions in VE. We di-

vided the participants into two groups of 10 persons.

The ﬁrst group performed the experiment to evalu-

ate the spherical guide, while the second group per-

formed the experiment to test the second guide( hat-

pic cone). The only constraint on the second group

was to select the object from the front. We gave each

user a short explanation about the task to perform and

how to make the interaction with VE via SPIDAR, but

no training trial was given to them. We recorded the

task’s completion time for each user. In order to carry

out subjective evaluation of the system we collected

the user’s response through a questionnaire contain-

ing the following questions.

1. To what extent the object selection was easy with-

out force Feedback? 2. To what extend do you think

that force feedback provided you guidance in object

selection? 3. Do you think, the interaction becomes

more realistic with force feedback?

The user had to respond to each of these questions on

a scale from 1 to 7. The scale was formatted accord-

ing to the table 1.

Table 1: Scale to respond to the questions.

Q1 Not easy 1-2-3-4-5-6-7 Very easy

Q2 No guidance 1-2-3-4-5-6-7 Guidance of high level

Q3 Not realistic 1-2-3-4-5-6-7 Very realistic

4.2 Experimental Task

The VE (see ﬁgure 5) contains four small objects(i.e

two spheres, teapot, clock) in the same vertical plane

and an other small sphere is used as 3D pointer whose

movement is directly controlled via SPIDAR. The ex-

periment starts when the user holds the spidar’s grip in

hand and the experimenter says ”GO”. The subjects

were asked to select an object and place it on the red

zone from where it comes back to its initial position

and the user selects it again. In this way each object is

selected and displaced ﬁve times in a single trial. All

users did exactly two trials of their respective experi-

ment. Two conditions were used for the experiment.

The ﬁrst condition make use of stereoscopic display

and visual guide while the second condition use hap-

tic guide plus stereo and visual guide. In both groups

half of the subjects performed the experiment under

ﬁrst condition in their ﬁrst trial while the second half

used the second condition in their ﬁrst trial.

Figure 5: Illustration of the environments used for experi-

ments.

4.3 Results and Analysis

4.3.1 Task Completion Time

In this section we present and analyze the results

based on both task completion time and user re-

sponses collected through questionnaire.The general

ANOVA for task completion time is (F(1,9)= 8.72, P

< 0.005) signiﬁcative.

Visual Sphere vs Haptic Sphere. Comparing the

performance of visual sphere with haptic one gives us

means of 55.7 and 46.0 with std(18.83,14.18) respec-

tively, for which ANOVA result is non signiﬁcant.

Visual Sphere vs Visual Cone. Comparing the task

completion time of the two visual guides, we have

means 55.77 and 84.88 with std (18.83, 20.93) for

sphere and cone respectively, showing non signiﬁcant

ANOVA result.

THE EFFECT OF HAPTIC GUIDES ON HUMAN PERFORMANCE IN VIRTUAL ENVIRONMENTS

325

Haptic Sphere vs Haptic Cone. Comparison of the

two haptic guides (sphere and cone) give means 46.44

and 69.66 with std (14.18, 12.74) respectively, having

ANOVA result as signiﬁcant.

The analysis of task completion time can be seen in

the ﬁgure 6, where

1: spherical guide(no haptic) + stereo display

2: spherical haptic guide + stereo display

3: Conical guide(no haptic) + stereo display

4: Conical haptic guide + stereo display

4.3.2 Subjective Evaluation

In this section we analyze the users’ responses and

comments collected through questionnaire. Summa-

rizing the response we observed that both visual and

haptic guides provide assistance to users in objects’

selection but they preferred haptic guides because of

their active nature. The spherical guide enabled them

to complete the task in lesser time as compared to the

conical one because it restricted the users to make se-

lection from a single direction for the sake of preci-

sion.

Figure 6: Task completion time & level of guidance under

various conditions.

5 CONCLUSIONS

In order to remove the inconveniences observed in

Follow-Me, we proposed haptic guides which not only

provide active guidance (attractive force toward the

object) to the user to select an object but also physi-

cally restricts his/her hand’s movement whenever re-

quired. We implemented two versions of haptic guide.

The spherical haptic guide that provides assistance in

object selection from all directions. The second is

a conical haptic guide which impart guidance when

the object selection is required from a speciﬁc direc-

tion. Here the guide not only gives attractive force

towards the object but also resist the exit of virtual

pointer through the walls of the cone. Two groups,

each composed of 10 young volunteers performed the

task to evaluate the haptic guides.

We observed for both types of haptic guides a reduc-

tion in task’s completion time, especially for the con-

ical haptic guide. It was also noted that task’s com-

pletion time increased in case of conical haptic guide

as compared to the spherical haptic guide.

Evaluating the subjective responses collected through

questionnaire, both the groups reported that haptic

guides provided them signiﬁcant guidance in object

selection, made the task easier and thus resulted in

increasing performance. Another important point is

that SPIDAR can be successfully used in large scale

virtual environment not only to have free movements

(without force) in the environment but also to gener-

ate realistic forces if required.

REFERENCES

Abbott, J. J., Marayong, P., and Okamura, A. M. (2005).

Haptic virtual ﬁxtures for robot-assisted manipulation.

In Proceedings of the 12th International Symposium

of Robotics Research, pages 49–64.

Alex B.Kuang, Shahram Payandeh, B. Z. F. H. C. L. S. F.

(2004). Assembling virtual ﬁxtures for guidance in

training environments. In 12th Interantional Sympo-

sium on Haptic Interfaces for Virtual Environments

and Teleoperator Systems, pages 367–374.

Bowman, D. (1999). Interaction Techniques for Common

Tasks in Immersive Virtual Environments : Design,

Evaluation, and Application. PhD thesis, Georgia In-

stitute of Technology.

Frees, S. and Kessler, G. (2005). Precise and rapid interac-

tion through scaled manipulation in immersive virtual

environments. In IEEE Virtual Reality, pages 99–106.

Ian Oakley, Alison Adams, S. B. and Gray, P. Guidelines

for the design of haptic widgets. In 16th British HCI

Group Annual Conference.

Liang, J. and Green, M. (1994). Jdcad: a highly interac-

tive 3d modeling system. In CAD/Graphics ’93, vol-

ume 18, pages 499–506.

Mine, M., Brooks, F., and Sequin, C. (1997). Moving

objects in space: exploiting proprioception in vir-

tualenvironment interaction. In Proceedings of SIG-

GRAPH97, pages 19–26.

Otmane, S., Mallem, M., Kheddar, A., and Chavand, F.

(2000a). Active virtual guide as an apparatus for aug-

mented reality based telemanipulation system on the

internet. In Proceedings of the 33rd IEEE Annual Sim-

ulation Symposium (ANSS2000), pages 185–191.

Otmane, S., Mallem, M., Kheddar, A., and Chavand,

F. (2000b). Ariti: an augmented reality interface

for teleopeation on the internet. In Proceedings of

the Advanced Simulation Technologies Conference

(ASTC2000, pages 254–261.

GRAPP 2009 - International Conference on Computer Graphics Theory and Applications

326

Ouramdane, N., Davesne, F., Otmane, S., and Mallem, M.

(2006). Follow-me: a new 3d interaction technique

based on virtual guides and granularity of interaction.

In 2nd ACM International Conference on Virtual Re-

ality Continuum and Its Applications (VRCIA 2006),

pages 137–144. ACM.

Pierce, J. S., Forsberg, A., Conway, M. J., Hong, S.,

Zeleznik, R., and Mine, M. R. (1997). Image plane

interaction techniques in 3d immersive environment.

In Proceedings of the 1997 symposium on Interactive

3D graphics, pages 39–44.

Poupyrev, I., Billinghurst, Mark andWeghorst, S., and

Ichikawa, T. (1996). The go-go interaction technique:

non-linear mapping for direct manipulation in vr. In

Proceedings of the 9th annual ACM symposium on

User interface software and technology, pages 79–80,

New York, NY, USA. ACM.

Poupyrev, I. and Ichikawa, T. (1999). Manipulation object

in virtual worlds: Categorization and empirical evalu-

ation of interaction techniques. Visual languages and

Computing, 10(1):19–35.

Poupyrev, I., Weghorst, S., Billinghurst, M., and Ichikawa,

T. (1998). Egocentric object manipulation in vir-

tual environment: Empirical evaluation of interaction

techniques. In Computer Graphics Forum, EURO-

GRAPHICS’98 Issue, pages 41–52.

Ren, J., Zhang, H., Patel, R. V., and Peters, T. M. (2007).

Haptics constrained motion for surgical intervention.

In Proceedings of Health Technology and Informatics,

pages 379–384.

Richard, P., Chamaret, D., Inglese, F.-X., Lucidarme, P.,

and Ferrier, J.-L. (2006). Human-scale virtual envi-

ronment for product design: Effect of sensory substi-

tution. The International Journal of Virtual Reality,

5:37–44.

Rosenberg, L. (1993). The use of virtual ﬁxtures to en-

hance telemanipulation with time delay. In Proceed-

ings of the ASME Winter Anual Meeting on Advances

in Robotics, Mechatronics, and Haptic Interfaces, vol-

ume 49, pages 29–36.

Sato, M. (2002). Development of string-based force dis-

play: Spidar. In International Conference on Virtual

Systems and MultiMedia (VSMM 2002).

Stoakley, R., Conway, M. J., and Pausch, R. (1995). Virtual

reality on a WIM: Interactive worlds in miniature. In

Proceedings of CHI95, pages 265–272.

Sturman, D. J., Zeltzer, D., and Pieper, S. (1989). Hands-on

interaction with virtual environments. In ACM Sym-

posium on User Interface Software and Technology,

pages 19–24.

Tarrin, N., Hasegawa, S., Bouguila, L., and Sato, M. (2003).

The stringed haptic workbench. In SIGGRAPH Com-

puter Graphics Forum, volume 22, pages 583–590.

THE EFFECT OF HAPTIC GUIDES ON HUMAN PERFORMANCE IN VIRTUAL ENVIRONMENTS

327