Ronan Boulic

• PhD
• Senior Scientist at Swiss Federal Institute of Technology in Lausanne

Investigating cybersickness (CS) in virtual reality (VR) often requires significant resources to create the VR environment and manage other experiment-related aspects. Additionally, slight differences in VR content across studies can lead to conflicting results. To address these challenges, we propose a standardized assessment framework to facilita...

The perception of one's own body is subject to systematic distortions and can be influenced by exposure to visual stimuli showing distorted bodies. In Virtual Reality (VR), echoing such body judgment inaccuracies, avatars with strong appearance dissimilarities with respect to users' bodies can be successfully embodied. The present experimental work...

This paper introduces the Least Increase aversion (LIA) protocol to investigate the relative impact of factors that may trigger cybersickness. The protocol is inspired by the Subjective Matching methodology (SMT) from which it borrows the incremental construction of a richer VR experience, except that the full-blown target experience may cause unde...

Objective. A key challenge of virtual reality (VR) applications is to maintain a reliable human-avatar mapping. Users may lose the sense of controlling (sense of agency), owning (sense of body ownership), or being located (sense of self-location) inside the virtual body when they perceive erroneous interaction, i.e. a break-in-embodiment (BiE). How...

In this research paper, we conducted a study to investigate the connection between three objective measures: Electrocardio-gram(ECG), Electrogastrogram (EGG), and Electroencephalogram (EEG), and individuals' susceptibility to cybersickness. Our primary objective was to identify which of these factors plays a central role in causing discomfort when...

The sense of embodiment in virtual reality (VR) is commonly understood as the subjective experience that one's physical body is substituted by a virtual counterpart, and is typically achieved when the avatar's body, seen from a first-person view, moves like one's physical body. Embodiment can also be experienced in other circumstances (e.g., in thi...

The brain mechanism of embodiment in a virtual body has grown a scientific interest recently, with a particular focus on providing optimal virtual reality (VR) experiences. Disruptions from an embodied state to a less- or non-embodied state, denominated Breaks in Embodiment (BiE), are however rarely studied despite their importance for designing in...

Studies of cybersickness (CS) often require a significant investment in creating the primary VR environment and other experiment-related features. In addition, minor differences in VR content in independent studies may lead to opposite results. This motivates us to introduce a standardized CS assessment framework to facilitate the development of CS...

The current study sought to objectively evaluate cybersickness by utilizing Electrogastrogram (EGG) physiological data in relation to three different navigation axes: Translational movement along the longitudinal and lateral axes, and rotation along the vertical Yaw axis. EGG was employed as it has been clinically identified as a valuable tool for...

The subjective experience of embodying an avatar when immersed in virtual reality (VR) is known to support the sense of presence and to help with the interaction in a virtual environment. Virtual embodiment is often thought of as the consequence of replacement of the physical body by a virtual one, with a sense of agency for the avatar obtained by...

In immersive Virtual Reality (VR), users can experience the subjective feeling of embodiment for the avatar representing them in a virtual world. This is known to be strongly supported by a high Sense of Agency (SoA) for the movements of the avatar that follows the user. In general, users do not self-attribute actions of their avatar that are diffe...

The brain mechanism of embodiment in a virtual body has grown a scientific interest recently, with a particular focus on providing optimal virtual reality (VR) experiences. Disruptions from an embodied state to a less- or non-embodied state, denominated Breaks in Embodiment (BiE), are however rarely studied despite their importance for designing in...

The perception of one’s own body is a complex mechanism that can be disturbed by conflicting sensory information and lead to illusory (mis-) perceptions. Prominent models of multisensory integration propose that sensory streams are integrated according to their reliability by approximating Bayesian inference. As such, when considering self-attribut...

In immersive Virtual Reality (VR), users can experience the subjective feeling of embodiment for the avatar representing them in a virtual world. This is known to be strongly supported by a high Sense of Agency (SoA) for the movements of the avatar that follows the user. In general, users do not self-attribute actions of their avatar that are diffe...

Cybersickness still poses a significant challenge to the widespread usage of virtual reality, leading to different levels of discomfort and potentially breaking the immersive experience. Researchers have attempted to discover the possible fundamental causes of cybersickness for years. Despite the longstanding interest in the research field, inconsi...

Providing Virtual Reality(VR) users with a 3D representation of their body complements the experience of immersion and presence in the virtual world with the experience of being physically located and more personally involved. A full-body avatar representation is known to induce a Sense of Embodiment (SoE) for this virtual body, which is associated...

Providing Virtual Reality(VR) users with a 3D representation of their body complements the experience of immersion and presence in the virtual world with the experience of being physically located and more personally involved. A full-body avatar representation is known to induce a Sense of Embodiment (SoE) for this virtual body, which is associated...

In Virtual Reality, having a virtual body opens a wide range of possibilities as the participant's avatar can appear to be quite different from oneself for the sake of the targeted application (e.g. for perspective-taking). In addition, the system can partially manipulate the displayed avatar movement through some distortion to make the overall exp...

The current approach to train Cardiopulmonary Resuscitation (CPR) is to employ a mannequin device replicating the physical properties of a real human head and torso. This aims to ensure a correct transfer of the cardiac massage location, amplitude and frequency in a real situation. However, this type of training does not replicate the stress that m...

Cybersickness is still an inevitable adverse effect when using VR systems, resulting in different levels of discomfort, and potentially breaking the immersive experience. To date, few studies have focused on exploring VR experience in the supine posture. Recent research indicated that simple adoption of VR game initially designed for a seated postu...

Cybersickness induced through Virtual Reality (VR) applications is still one of its main barriers as it can induce unwanted side-effects in players, significantly hindering the overall experience. Despite the wealth of research available on this topic, it is still an unsolved problem. Although previous studies have explored methods of cybersickness...

Over the past few years scientific research has opened up to the idea of using digital games for human-based studies. Fields such as Neuroscience, Medical and Affective Computing are currently using games to study human-based phenomena. Even though a vast amount of work exists within the field, rarely is the subject of designing such games ever tou...

Cybersickness continues to be one of the main barriers for mainstream adoption of Virtual Reality (VR). Despite the wealth of research available on this topic, it is still an unsolved problem. This paper explores the potential influence of cybersickness over the course of a VR experience on player Blink-Rate. This investigation was conducted on the...

Hands deserve particular attention in virtual reality (VR) applications because they represent our primary means for interacting with the environment. Although marker-based motion capture works adequately for full body tracking, it is less reliable for small body parts such as hands and fingers which are often occluded when captured optically, thus...

Hands deserve particular attention in virtual reality (VR) applications because they represent our primary means for interacting with the environment. Although marker-based motion capture with inverse kinematics works adequately for full body tracking, it is less reliable for small body parts such as hands and fingers which are often occluded when...

This study explores the extent to which individuals embodied in Virtual Reality tend to self-attribute the movements of their avatar. More specifically, we tested subjects performing goal-directed movements and distorted the mapping between user and avatar movements by decreasing or increasing the amplitude of the avatar hand movement required to r...

We investigate the self-attribution of distorted pointing movements in immersive virtual reality. Participants had to complete a multi-directional pointing task in which the visual feedback of the tapping finger could be deviated in order to increase or decrease the motor size of a target relative to its visual appearance. This manipulation effecti...

With the broad range of motion capture devices available on the market, it is now commonplace to directly control the limb movement of an avatar during immersion in a virtual environment. Here, we study how the subjective experience of embodying a full-body controlled avatar is influenced by motor alteration and self-contact mismatches. Self-contac...

Empirical research on the bodily self has shown that the body representation is malleable, and prone to manipulation when conflicting sensory stimuli are presented. Using Virtual Reality (VR) we assessed the effects of manipulating multisensory feedback (full body control and visuo-tactile congruence) and visual perspective (first and third person...

Example of the GSR signal of a complete session. (PDF)

Overview of the experimental setup and conditions. (MP4)

Session protocol. Video used to instruct the subject about the stages of a session. (MP4)

Reported sense of self-location at different levels of perspective and perspective order factors. (PDF)

Summary of results: Mean and confidence interval per experimental condition. (PDF)

Performance comparison of the reaching task (VMT group only). (PDF)

Summary of statistical tests results and their respective effect size estimations. (PDF)

Data sets obtained with this experiment. (ZIP)

In this paper, we propose a new approach for the classification of reaching targets before movement onset, during visually-guided reaching in 3D space. Our approach combines the discriminant power of two-dimensional Electroencephalography (EEG) signals (i.e., EEG images) built from short epochs, with the feature extraction and classification capabi...

Many on-line communities still rely on text messages as their privileged medium of communication and we believe it will remain so even if it can be complemented by images and video. Previous chapters have described how to infer emergent emotion dynamics from text corpus whereas we focus here on the instantaneous display of a detected emotion with a...

Creating interactive characters is one of the most challenging tasks of videogame design. In order to facilitate such an endeavour, we introduce a decisional and behaviour synthesis architecture integrated in the game engine Unity3D. A distinguishing feature of this architecture is that it embraces embodied cognition principles and uses them as imp...

The relative location of human body parts often materializes the semantics of on-going actions, intentions and even emotions expressed, or performed, by a human being. However, traditional methods of performance animation fail to correctly and automatically map the semantics of performer postures involving self-body contacts onto characters with di...

The use of expressive Virtual Characters is an effective complementary means of communication for social networks offering multi-user 3D-chatting environment. In such contexts, the facial expression channel offers a rich medium to translate the ongoing emotions conveyed by the text-based exchanges. However, until recently, only purely symmetric fac...

The locomotion pattern is characterized by a translation displacement mostly occurring along the forward frontal body direction, whereas local repositioning with large re-orientations, i.e. stepping, may induce translations both along the frontal and the lateral body directions (holonomy). We consider here a stepping pattern with initial and final...

In this paper we present an intuitive tool suitable for 2D artists using touch-enabled pen tablets. An artist-oriented tool should be easy-to-use, real-time, versatile, and locally refinable. Our approach uses an interactive system for 3D character posing from 2D strokes. We employ a closed-form solution for the 2D strokes to 3D skeleton registrati...

In this article, we present a parallel prioritized Jacobian-based inverse kinematics algorithm for multithreaded architectures. We solve damped least squares inverse kinematics using a parallel line search by identifying and sampling critical input parameters. Parallel competing execution paths are spawned for each parameter in order to select the...

Photorealistic animation is a desirable technique for computer games and movie production. We propose a new method to synthesize plausible videos of human actors with new motions using a single cheap RGB-D camera. A small database is captured in a usual office environment, which happens only once for synthesizing different motions. We propose a mar...

In this paper we evaluate the use of non-planar projections as a means to increase the Field of View (FoV) in embodied Virtual Reality (VR). Our main goal is to bring the virtual body into the user's FoV and to understand how this affects the virtual body/environment relation and quality of interaction. Subjects wore a Head Mounted Display (HMD) an...

Third Person Perspective (3PP) viewpoints have the potential to expand how one perceives and acts in a virtual environment. They offer increased awareness of the posture and of the surrounding of the virtual body as compared to First Person Perspective (1PP). But from another standpoint, 3PP can be considered as less effective for inducing a strong...

We conducted an exploratory study to better understand free-space stepping for short range change of position and orientation within a maximum radius of 40% of the body height. Twenty subjects have each performed 386 of such relocation tasks. We look at the choice of starting foot that the subjects could take depending on the relative positions and...

In this paper we propose the Middle-Axis-Rotation (MAR) parametrization of human limbs that addresses the ill-conditioned cases of analytical Inverse Kinematics (IK) algorithms. The MAR parametrization is singularity-free in the reach space of the human limbs. Unlike the swivel representation, it does not rely on the projection of an additional fix...

In this paper, we propose a method to achieve effective facial emotional expressivity for embodied conversational agents by considering two types of asymmetry when exploiting the valence–arousal–dominance representation of emotions. Indeed, the asymmetry of facial expressions helps to convey complex emotional feelings such as conflicting and/or hid...

Following limb loss, patients usually continue having sensations on their missing limbs as if they were still present. Significant amount of such sensations are painful and referred as Phantom Limb Pain (PLP). Previous research has shown that providing the patient with the visual feedback of a limb at the place of the missing one in Virtual Reality...

We present the disambiguation canvas, a technique developed for easy, accurate and fast selection of small objects and objects inside cluttered virtual environments. Disambiguation canvas rely on selection by progressive refinement, it uses a mobile device and consists of two steps. During the first, the user defines a subset of objects by means of...

We explore an approach to full-body motion editing with linear motion models, prioritized constraint-based optimization and latent-space interpolation. By exploiting the mathematical connections between linear motion models and prioritized inverse kinematics (PIK), we formulate and solve the motion editing problem as an optimization function whose...

We present Disambiguation canvas, a technique for selection by progressive refinement using a mobile device and consisting of two steps. During the first, the user defines a subset of objects through the orientation sensors of the device and a volume-casting pointing technique. The subsequent step consists of the disambiguation of the desired targe...

While designing an animation engine usable in crowd simulations, several criteria have to be taken into account: animation computation should be efficient and scalable, it should allow for variability, and it should be compatible with levels of detail. To understand the problems, let us take the most important animation pattern used in crowd simula...

In this paper, we first present our crowd simulation method, Trajectory Variant Shift (TVS) based on real pedestrian trajectories re-use. We detail how to re-use and shift these trajectories to avoid collisions while retaining the liveliness of captured data. Second, we conducted a user study in a four-screen CAVE to compare our approach with three...

Achieving effective facial emotional expressivity within a real-time rendering constraint requests to leverage on all possible inspiration sources and especially from the observations of real individuals. One of them is the frequent asymmetry of facial expressions of emotions, which allows to express complex emotional feelings such as suspicion, sm...

This paper proposes a new emotional model for Virtual Humans (VHs) in a conversational environment. As a part of a multi-users emotional 3D-chatting system, this paper focus on how to formulate and visualize the flow of emotional state defined by the Valence-Arousal-Dominance (VAD) parameters. From this flow of emotion over time, we successfully vi...

Non-verbal communication (NVC) makes up about two-thirds of all communication between two people or between one speaker and a group of listeners. However, this fundamental aspect of communicating is mostly omitted in 3D social forums or virtual world oriented games. This paper proposes an answer by presenting a multi-user 3D-chatting system enriche...

Computer-based simulations of human hip joints generally include investigating contacts happening among soft or hard tissues during hip movement. In many cases, hip movement is approximated as rotation about an estimated hip center. In this paper, we investigate the effect of different methods used for estimating hip joint center of rotation on the...

Stepping is a class of complex coordinated movements allowing a standing individual to relocate oneself locally with a potentially large body reorientation. Being a key component of numerous higher-level activities, it deserves to be studied for itself. Due to the local nature of the relocation such stepping movement is holonomic, i.e. one exploits...

The Immersive Interaction Group aims at ensuring active presence through the transparent performance of complex full-body actions in potentially complex environments

This paper is motivated by the objective of improving the realism of real-time simulated crowds by reducing short term collision avoidance through long term anticipation of pedestrian trajectories. For this aim, we choose to reuse outdoor pedestrian trajectories obtained with non-invasive means. This initial step is achieved by analyzing the record...

Despite the large success of games grounded on movement-based interactions the current state of full-body motion capture technologies still prevents the exploitation of precise interactions with complex environments. The first key requirement in the line of work we present here is to ensure a precise spatial correspondence between the user and the...

Our goal is to create dancing crowds in cyber worlds and to use this feature to support creative endeavors such as pre-visualization of choreography and actual stage performances. In this paper we present a method of motion planning using dance motion clips. We describe a trial algorithm of collision avoidance using a grid map. We also present meth...

We are interested in developing real-time applications such as games or virtual prototyping that take advantage of the user full-body input to control a wide range of entities, from a self-similar avatar to any type of animated characters, including virtual humanoids with differing size and proportions. The key issue is, as always in real-time inte...

We introduce a new method for computerized real-time evaluation of femoroacetabular impingement (FAI). In contrast to previously presented stress analyses, this method is based on two types of predictions of penetration depths for two rotating bodies: curvilinear and radial penetration depth. This intuitive method allows the analysis of both bony a...

The growth of motion capture systems have contributed to the proliferation of human motion database, mainly because human mo- tion is important in many applications, ranging from games entertain- ment and films to sports and medicine. However, the captured motions normally attend specific needs. As an effort for adapting and reusing cap- tured huma...

Despite the large success of games grounded on movement-based interactions the current state of full body motion capture technologies still prevents the exploitation of precise interactions with complex environments. This paper focuses on ensuring a precise spatial correspondence between the user and the avatar. We build upon our past effort in hum...

Hip mechanical simulation for estimating pressures within the soft tissues during the loads and motions of daily activities is a common approach to investigate hip joint pathology. Many computational approaches estimate the pressure and contact pressures via finite element methods (FEM) by using 3D meshes of the tissues. Although this type of simul...

Today, to create and to simulate a virtual anatomical version of a subject is useful in the decision process of surgical treatments. The muscular activity is one of the factors which can contribute to abnormal movements such as in spasticity or static contracture. In this paper, we propose a numerical solution, based on the Finite Element (FE) meth...

Interactive control of a virtual character through full-body movement has a wide range of applications. However, there is a need for systems that accurately reproduce a performer's motion while accounting for surrounding obstacles. The authors propose an approach based on a Prioritized Inverse Kinematics (IK) constraint solver. Several markers plac...

In this paper, we propose a hybrid postural control approach taking advantage of data-driven and goal-oriented methods while overcoming their limitations. In particular, we take advantage of the latent space characterizing a given motion database. We introduce a motion constraint operating in the latent space to benefit from its much smaller dimens...

In this paper a model is proposed to evaluate individually the normalized fatigue at the joint level. More specifically our model distinguishes the two antagonist muscle groups acting for each degree of freedom (in short dof). The fatigue model parameters are normalized torques, joint strength and the maximum holding time that a posture can be main...