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Taming Mona Lisa: communicating gaze faithfully in 2D and 3D facial projections
KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Speech Communication and Technology.
KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Speech Communication and Technology.ORCID iD: 0000-0001-9327-9482
KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Speech Communication and Technology.ORCID iD: 0000-0003-1399-6604
2012 (English)In: ACM Transactions on Interactive Intelligent Systems, Vol. 1, no 2, 25- p.Article in journal (Refereed) Published
Abstract [en]

The perception of gaze plays a crucial role in human-human interaction. Gaze has been shown to matter for a number of aspects of communication and dialogue, especially for managing the flow of the dialogue and participant attention, for deictic referencing, and for the communication of attitude. When developing embodied conversational agents (ECAs) and talking heads, modeling and delivering accurate gaze targets is crucial. Traditionally, systems communicating through talking heads have been displayed to the human conversant using 2D displays, such as flat monitors. This approach introduces severe limitations for an accurate communication of gaze since 2D displays are associated with several powerful effects and illusions, most importantly the Mona Lisa gaze effect, where the gaze of the projected head appears to follow the observer regardless of viewing angle. We describe the Mona Lisa gaze effect and its consequences in the interaction loop, and propose a new approach for displaying talking heads using a 3D projection surface (a physical model of a human head) as an alternative to the traditional flat surface projection. We investigate and compare the accuracy of the perception of gaze direction and the Mona Lisa gaze effect in 2D and 3D projection surfaces in a five subject gaze perception experiment. The experiment confirms that a 3D projection surface completely eliminates the Mona Lisa gaze effect and delivers very accurate gaze direction that is independent of the observer's viewing angle. Based on the data collected in this experiment, we rephrase the formulation of the Mona Lisa gaze effect. The data, when reinterpreted, confirms the predictions of the new model for both 2D and 3D projection surfaces. Finally, we discuss the requirements on different spatially interactive systems in terms of gaze direction, and propose new applications and experiments for interaction in a human-ECA and a human-robot settings made possible by this technology.

Place, publisher, year, edition, pages
2012. Vol. 1, no 2, 25- p.
National Category
Computer Science Language Technology (Computational Linguistics)
URN: urn:nbn:se:kth:diva-106994DOI: 10.1145/2070719.207072OAI: diva2:574371

tmh_import_12_12_05, tmh_id_3542. Updated from "In press" to "Published"

 QC 20121210

Available from: 2012-12-05 Created: 2012-12-05 Last updated: 2012-12-10Bibliographically approved
In thesis
1. Bringing the avatar to life: Studies and developments in facial communication for virtual agents and robots
Open this publication in new window or tab >>Bringing the avatar to life: Studies and developments in facial communication for virtual agents and robots
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The work presented in this thesis comes in pursuit of the ultimate goal of building spoken and embodied human-like interfaces that are able to interact with humans under human terms. Such interfaces need to employ the subtle, rich and multidimensional signals of communicative and social value that complement the stream of words – signals humans typically use when interacting with each other.

The studies presented in the thesis concern facial signals used in spoken communication, and can be divided into two connected groups. The first is targeted towards exploring and verifying models of facial signals that come in synchrony with speech and its intonation. We refer to this as visual-prosody, and as part of visual-prosody, we take prominence as a case study. We show that the use of prosodically relevant gestures in animated faces results in a more expressive and human-like behaviour. We also show that animated faces supported with these gestures result in more intelligible speech which in turn can be used to aid communication, for example in noisy environments.

The other group of studies targets facial signals that complement speech. As spoken language is a relatively poor system for the communication of spatial information; since such information is visual in nature. Hence, the use of visual movements of spatial value, such as gaze and head movements, is important for an efficient interaction. The use of such signals is especially important when the interaction between the human and the embodied agent is situated – that is when they share the same physical space, and while this space is taken into account in the interaction.

We study the perception, the modelling, and the interaction effects of gaze and head pose in regulating situated and multiparty spoken dialogues in two conditions. The first is the typical case where the animated face is displayed on flat surfaces, and the second where they are displayed on a physical three-dimensional model of a face. The results from the studies show that projecting the animated face onto a face-shaped mask results in an accurate perception of the direction of gaze that is generated by the avatar, and hence can allow for the use of these movements in multiparty spoken dialogue.

Driven by these findings, the Furhat back-projected robot head is developed. Furhat employs state-of-the-art facial animation that is projected on a 3D printout of that face, and a neck to allow for head movements. Although the mask in Furhat is static, the fact that the animated face matches the design of the mask results in a physical face that is perceived to “move”.

We present studies that show how this technique renders a more intelligible, human-like and expressive face. We further present experiments in which Furhat is used as a tool to investigate properties of facial signals in situated interaction.

Furhat is built to study, implement, and verify models of situated and multiparty, multimodal Human-Machine spoken dialogue, a study that requires that the face is physically situated in the interaction environment rather than in a two-dimensional screen. It also has received much interest from several communities, and been showcased at several venues, including a robot exhibition at the London Science Museum. We present an evaluation study of Furhat at the exhibition where it interacted with several thousand persons in a multiparty conversation. The analysis of the data from the setup further shows that Furhat can accurately regulate multiparty interaction using gaze and head movements.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. xxvi, 96 p.
Trita-CSC-A, ISSN 1653-5723 ; 2012:15
Avatar, Speech Communication, Facial animation, Nonverbal, Social, Robot, Human-like, Face-to-face, Prosody, Pitch, Prominence, Furhat, Gaze, Head-pose, Dialogue, Interaction, Multimodal, Multiparty
National Category
Human Computer Interaction
Research subject
urn:nbn:se:kth:diva-105605 (URN)978-91-7501-551-4 (ISBN)
Public defence
2012-12-07, F3, Lindstedtsvägen 26, KTH, Stockholm, 13:30 (English)

QC 20121123

Available from: 2012-11-23 Created: 2012-11-22 Last updated: 2012-12-10Bibliographically approved

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Al Moubayed, SamerEdlund, JensBeskow, Jonas
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