full Paper - Nguyen Dang Binh

EUROGRAPHICS 2005 Tutorial
1. abstract
Haptic Interfaces:Collocation and Coherence Issues
Multi-modality, collocation and immersive VE nowadays
represents the break-trough barrier of human computer
interaction. Typical VE systems synthesize the information
to be presented to the user by means of different algorithms
and present them using different interfaces. On the other
hand the human perceptive system is strongly integrated and
“fatigues” to interpret these stimuli as belonging to a unique
information source.
Collocation and coherence issues may be noticed in any
kind of multimodal integration: “visual and audio”, “visual
and vestibular”, “audio and haptic”, “visual and haptic”,...
The present paper deals with two speci£c kinds of multimodal
integration: “visual and haptic” and “haptic and
haptic”. The coherence problem of synchronizing several
haptic devices is analyzed and an optimized solution is
proposed. The proposed solution has been tested on a dual
point HI, behaving a wide workspace realized at PERCRO.
More speci£cally the present paper will present a novel
algorithm to achieve the absolute coordination of multiple
HI working in the same VE. The system performances have
been assessed and compared to those of existing solutions.
The achieved results have been exploited for the EU project
GRAB † . The GRAB project investigates to which extent a
purely haptic environment can be employed from sightless
users.
Index Terms - Haptic Interface; coherence.
2. Introduction
Visual Display Terminal technologies (VDT) i.e. screen,
keyboard and mouse, represent the most spread systems
for the human computer interaction (HCI). Such technologies
are the classical example of non-collocated and non-
† The GRAB project has been carried on within the 5th framework
program of the EU. The IST and the European Union are acknowledged
for their grants in sustaining the GRAB research.
c○ The Eurographics Association 2005.
C.A. Avizzano, S. Marcheschi, M. Bergamasco
Superiore S. Anna, Pisa, Italy
59
Figure 1: Collocation & Coherence in multipoint HI
coherent systems. Collocated feedback required that the information
is produced (or given) in the place where the generating
action are exerted. Coherent feedback is more related
to timing and physical aspects of the interaction and implies
that the given feedback is strictly related to the generating
action (Fig. 1). Almost all the experiences the user probes in
a real world have these two key elements, but the HCI interaction
introduces the possibility of altering them. As shown
in the scienti£c literature, the missing of these two factors
implies that the user brain has to compensate for them resulting
in a sort of “mental load” which varies largely according
to the application.
When the multimodal integration is very strong, as for
as the case of vestibular and visual information (typical
in vehicle simulator), the presence of incoherent feedback
may cause also several physical sickness. Therefore, mouse,
video and keyboard are not the optimal way for interacting
with computers. In the case of VDT, the popularity of these
interfaces is ensured by the fact that the associated mental
load is very low because very low is the information content
associated to the interaction. This is no more true whenever
the degree of interaction between user and computer
increases to higher complexities or includes different perceptive
channels.