Section: New Results

3D User Interfaces

3D manipulation of virtual objects

Evaluation of Direct Manipulation using Finger Tracking for Complex Tasks in an Immersive Cube Maud Marchal, Collaboration with REVES

We have proposed a solution for interaction using finger tracking in a cubic immersive virtual reality system (or immersive cube)  [13] . Rather than using a traditional wand device, users can manipulate objects with fingers of both hands in a close-to-natural manner for moderately complex, general purpose tasks. Our solution couples finger tracking with a real-time physics engine, combined with a heuristic approach for hand manipulation, which is robust to tracker noise and simulation instabilities. A first study has been performed to evaluate our interface, with tasks involving complex manipulations, such as balancing objects while walking in the cube. The users finger-tracked manipulation was compared to manipulation with a 6 degree-of-freedom wand (or flystick), as well as with carrying out the same task in the real world. Users were also asked to perform a free task, allowing us to observe their perceived level of presence in the scene. Our results show that our approach provides a feasible interface for immersive cube environments and is perceived by users as being closer to the real experience compared to the wand. However, the wand outperforms direct manipulation in terms of speed and precision. We conclude with a discussion of the results and implications for further research

A New Direct Manipulation Technique for Immersive 3D Virtual Environments Thi Thuong Huyen Nguyen, Thierry Duval, Collaboration with MIMETIC

We have introduced a new 7-Handle manipulation technique [38] for 3D objects in immersive virtual environments and its evaluation. The 7-Handle technique includes a set of seven points which are flexibly attached to an object. There are three different control modes for these points including configuration, manipulation and locking/ unlocking modes. We have conducted an experiment to compare the efficiency of this technique with the traditional 6-DOF direct manipulation technique in terms of time, discomfort metrics and subjective estimation for precise manipulations in an immersive virtual environment in two consecutive phases: an approach phase and a refinement phase. The statistical results showed that the completion time in the approach phase of the 7-Handle technique was significantly longer than the completion time of the 6-DOF technique. Nevertheless, we found a significant interaction effect between the two factors (the manipulation technique and the object size) on the completion time of the refinement phase. In addition, even though we did not find any significant differences between the two techniques in terms of intuitiveness, ease of use and global preference in the result of subjective data, we obtained a significantly better satisfaction feedback from the subjects for the efficiency and fatigue criteria.

A survey of plasticity in 3D user interfaces Jérémy Lacoche, Thierry Duval, Bruno Arnaldi, Collaboration with b<>com

Plasticity of 3D user interfaces [33] refers to their capabilities to automatically fit to a set of hardware and environmental constraints. This area of research has already been deeply explored in the domain of traditional 2D user interfaces. Besides, during the last decade, interest in 3D user interfaces has grown. Designers find with 3D user interfaces new ways to promote and interact with data, such as e-commerce websites, scientific data visualization, etc. Because of the wide variety of Virtual Reality (VR) and Augmented Reality (AR) applications in terms of hardware, data and target users, there is a real interest in solutions for automatic adaption in order to improve the user experience in any context while reducing the development costs. An adaptation is performed in reaction to different criteria defining a system such as the targeted hardware platform, the user’s context and the structure and the semantic of the manipulated data. This adaptation can then impact the system in different ways, especially content presentation, interaction techniques modifications and eventually the current distribution of the system across a set of available devices. In [33] we present the state of the art about plastic 3D user interfaces. Moreover, we present well known methods in the field of 2D user interfaces that could become relevant for 3D user interfaces.

Navigating in virtual environments

Adaptive Navigation in Virtual Environments Ferran Argelaguet

Navigation speed for most navigation interfaces is still determined by rate-control devices (e.g. joystick). The interface designer is in charge of adjusting the range of optimal speeds according to the scale of the environment and the desired user experience. However, this approach is not valid for complex environments (e.g. multi-scale environments). Optimal speeds might vary for each section of the environment, leading to non-desired side effects such as collisions or simulator sickness. Thereby, we proposed a speed adaptation algorithm [24] based on the spatial relationship between the user and the environment and the user’s perception of motion. The computed information is used to adjust the navigation speed in order to provide an optimal navigation speed and avoid collisions. Two main benefits of our approach is firstly, the ability to adapt the navigation speed in multi-scale environments and secondly, the capacity to provide a smooth navigation experience by decreasing the jerkiness of described trajectories. The evaluation showed that our approach provides comparable performance as existing navigation techniques but it significantly decreases the jerkiness of described trajectories

Novel pseudo-haptic based interfaces

Toward “Pseudo-Haptic Avatars”: Modifying the Visual Animation ofSelf-Avatar Can Simulate the Perception of Weight Lifting, Ferran Argelaguet, Anatole Lécuyer, Collaboration with MIMETIC

We have studied how the visual animation of a self-avatar can be artificially modified in real-time in order to generate different haptic perceptions [18] . In our experimental setup, participants could watch their self-avatar in a virtual environment in mirror mode while performing a weight lifting task. Users could map their gestures on the self-animated avatar in real-time using a Kinect. We introduce three kinds of modification of the visual animation of the self-avatar according to the effort delivered by the virtual avatar: 1) changes on the spatial mapping between the user’s gestures and the avatar, 2) different motion profiles of the animation ,and 3) changes in the posture of the avatar (upper-body inclination). The experimental task consisted of a weight lifting task in which participants had to order four virtual dumbbells according to their virtual weight. The user had to lift each virtual dumbbells by means of a tangible stick, the animation of the avatar was modulated according to the virtual weight of the dumbbell. The results showed that the altering the spatial mapping delivered the best performance. Nevertheless, participants globally appreciated all the different visual effects. Our results pave the way to the exploitation of such novel techniques in various VR applications such as sport training, exercise games, or industrial training scenarios in single or collaborative mode.

The Virtual Mitten: A Novel Interaction Paradigm for Visuo-Haptic Manipulation of Objects Using Grip Force Merwan Achibet, Maud Marchal, Ferran Argelaguet, Anatole Lécuyer

We have proposed a novel visuo-haptic interaction paradigm called the “Virtual Mitten” [22] for simulating the 3D manipulation of objects. Our approach introduces an elastic handheld device that provides a passive haptic feedback through the fingers and a mitten interaction metaphor that enables to grasp and manipulate objects. The grasping performed by the mitten is directly correlated with the grip force applied on the elastic device and a supplementary pseudo-haptic feedback modulates the visual feedback of the interaction in order to simulate different haptic perceptions. The Virtual Mitten allows natural interaction and grants users with an extended freedom of movement compared with rigid devices with limited workspaces. Our approach has been evaluated within two experiments focusing both on subjective appreciation and perception. Our results show that participants were able to well perceive different levels of effort during basic manipulation tasks thanks to our pseudo-haptic approach. They could also rapidly appreciate how to achieve different actions with the Virtual Mitten such as opening a drawer or pulling a lever. Taken together, our results suggest that our novel interaction paradigm could be used in a wide range of applications involving one or two-hand haptic manipulation such as virtual prototyping, virtual training or video game.

Collaborative Pseudo-Haptics: Two-User Stiffness Discrimination Based on Visual Feedback Ferran Argelaguet, Takuya Sato, Thierry Duval, Anatole Lécuyer, Collaboration with Tohoku University Research Institute of Electrical Communication

We have explored how the concept of pseudo-haptic feedback can be introduced in a collaborative scenario [25] . A remote collaborative scenario in which two users interact with a deformable object is presented. Each user, through touch-based input, is able to interact with a deformable virtual object displayed in a standard display screen. The visual deformation of the virtual object is driven by a pseudo-haptic approach taking into account both the user in-put and the simulated physical properties. Particularly, we investigated stiffness perception. In order to validate our approach, we tested our system in a single and two-user configuration. The results showed that users were able to discriminate the stiffness of the virtual object in both conditions with a comparable performance. Thus, pseudo-haptic feedback seems a promising tool for providing multiple users with physical information related to other users' interactions.

Sound and virtual reality

Sonic interaction with a virtual orchestra of factory machinery Florian Nouviale, Valérie Gouranton, collaboration with Ronan Gaugne (IMMERSIA) and LIMSI

We have conceived an immersive application where users receive sound and visual feedbacks on their interactions with a virtual environment. In this application, the users play the part of conductors of an orchestra of factory machines since each of their actions on interaction devices triggers a pair of visual and audio responses. Audio stimuli were spatialized around the listener. The application was exhibited during the 2013 Science and Music day and designed to be used in a large immersive system with head tracking, shutter glasses and a 10.2 loudspeaker configuration [43] .

Audio-Visual Attractors for Capturing Attention to the Screens When Walking in CAVE Systems Ferran Argelaguet, Valérie Gouranton, Anatole Lécuyer, collaboration with Aalborg University

In four-sided CAVE-like VR systems, the absence of the rear wall has been shown to decrease the level of immersion and can introduce breaks in presence. We have therefore investigated to which extent user's attention can be driven by visual and auditory stimuli in a four-sided CAVE-like system [32] . An experiment was conducted in order to analyze how user attention is diverted while physically walking in a virtual environment, when audio and/or visual attractors are present. The four sided CAVE used in the experiment allowed to walk up to 9m in straight line. An additional key feature in the experiment is the fact that auditory feedback was delivered through binaural audio rendering techniques via non-personalized head related transfer functions (HRTFs). The audio rendering was dependent on the user's head position and orientation, enabling localized sound rendering. The experiment analyzed how different "attractors" (audio and/or visual, static or dynamic) modify the user's attention. The results of the conducted experiment show that audio-visual attractors are the most efficient attractors in order to keep the user's attention toward the inside of the CAVE. The knowledge gathered in the experiment can provide guidelines to the design of virtual attractors in order to keep the attention of the user and avoid the "missing wall".

Experiencing the past in virtual reality

Immersia, an open immersive infrastructure: doing archaeology in virtual reality Valérie Gouranton, Bruno Arnaldi, collaboration with MIMETIC and Ronan Gaugne (IMMERSIA)

We have first studied the mutual enrichment between archaeology and virtual reality [16] . To do so, we are considering Immersia, our open high-end platform dedicated to research on immersive virtual reality and its usages. Immersia is a node of the european project Visionair that offers an infrastructure for high level visualisation facilities open to research communities across Europe. In Immersia, two projects are currently active on the theme of archaeology. One is relative to the study of the Cairn of Carn, with the Creaah, a pluridisciplinary research laboratory of archeology and archeosciences, and one on the reconstitution of the gallo-roman villa of Bais, with the French institute INRAP.

Virtual reality tools for the West Digital Conservatory of Archaeological Heritage Jean-Baptiste Barreau, Valérie Gouranton, collaboration with Ronan Gaugne (IMMERSIA) and INRAP

In continuation of the 3D data production work made by the WDCAH (West Digital Conservatory of Archaeological Heritage), the use of virtual reality tools allows archaeologists to carry out analysis and understanding research about their sites. We have then focused on the virtual reality services proposed to archaeologists in the WDCAH, through the example of two archaeological sites, the Temple de Mars in Corseul and the Cairn of Carn Island [27] .

Preservative Approach to Study Encased Archaeological Artefacts Valérie Gouranton, Bruno Arnaldi, collaboration with Ronan Gaugne (IMMERSIA) and INRAP

We have proposed a workflow based on a combination of computed tomography, 3D images and 3D printing to analyse different archaeological material dating from the Iron Age, a weight axis, a helical piece, and a fibula [39] . This workflow enables a preservative analysis of the artefacts that are unreachable because encased either in stone, corrosion or ashes. Computed tomography images together with 3D printing provide a rich toolbox for archaeologist work allowing to access a tangible representation of hidden artefacts. These technologies are combined in an efficient, affordable and accurate workflow compatible with preventive archaeology constraints.

Combination of 3D Scanning, Modeling and Analyzing Methods around the Castle of Coatfrec Reconstitution Jean Baptiste Barreau, Valérie Gouranton, collaboration with Ronan Gaugne (IMMERSIA) and INRAP

The castle of Coatfrec is a medieval castle in Brittany constituting merely a few remaining ruins currently in the process of restoration. Beyond its great archeological interest, it has become, over the course of the last few years, the subject of experimentation in digital archeology. Methods of 3D scanning were used in order to gauge comparisons between the remaining structures and their absent hypothetical ones, resulting in the first quantitative results of its kind. We have applied these methods and presented the subsequent results obtained using these new digital tools [26] .

Ceramics Fragments Digitization by Photogrammetry, Reconstructions and Applications Jean Baptiste Barreau, Valérie Gouranton, collaboration with Ronan Gaugne (IMMERSIA) and INRAP

We have studied an application of photogrammetry on ceramic fragments from two excavation sites located north-west of France [28] . The restitution by photogrammetry of these different fragments allowed reconstructions of the potteries in their original state or at least to get to as close as possible. We used the 3D reconstructions to compute some metrics and to generate a presentation support by using a 3D printer. This work is based on affordable tools and illustrates how 3D technologies can be quite easily integrated in archaeology process with limited financial resources.