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Item Elasticity-based Clustering for Haptic Interaction with Heterogeneous Deformable Objects(The Eurographics Association, 2017) Gouis, BenoĂ®t Le; Marchal, Maud; LĂ©cuyer, Anatole; Arnaldi, Bruno; Fabrice Jaillet and Florence ZaraPhysically-based simulation of heterogeneous objects remains computationally-demanding for many applications, especially when involving haptic interaction with virtual environments. In this paper, we introduce a novel multiresolution approach for haptic interaction with heterogeneous deformable objects. Our method called "Elasticity-based Clustering" is based on the clustering and aggregation of elasticity inside an object, in order to create large homogeneous volumes preserving important features of the initial distribution. The design of such large and homogeneous volumes improves the attribution of elasticity to the elements of the coarser geometry. We could successfully implement and test our approach within a complete and real-time haptic interaction pipeline compatible with consumer-grade haptic devices. We evaluated the performance of our approach on a large set of elasticity configurations using a perception-based quality criterion. Our results show that for 90% of studied cases our method can achieve a 6 times speedup in the simulation time with no theoretical perceptual difference.Item Towards Biomechanically and Visually Plausible Volumetric Cutting Simulation of Deformable Bodies(The Eurographics Association, 2019) Qian, Yinling; Huang, Wenbin; Si, Weixin; Liao, Xiangyun; Wang, Qiong; Heng, Pheng-Ann; Lee, Jehee and Theobalt, Christian and Wetzstein, GordonDue to the simplicity and high efficiency, composited finite element method(CFEM) based virtual cutting attracted much attention in the field of virtual surgery in recent years. Even great progress has been made in volumetric cutting of deformable bodies, there are still several open problems restricting its applications in practical surgical simulator. First among them is cutting fracture modelling. Recent methods would produce cutting surface immediately after an intersection between the cutting plane and the object. But in real cutting, biological tissue would first deform under the external force induced by scalpel and then fracture occurs when the stress exceeds a threshold. Secondly, it's computation-intensive to reconstruct cutting surface highly consistent with the scalpel trajectory, since reconstructed cutting surface in CFEM-based virtual cutting simulation is grid-dependent and the accuracy of cutting surface is proportional to the grid resolution. This paper propose a virtual cutting method based on CFEM which can effectively simulate cutting fracture in a biomechanically and visually plausible way and generate cutting surface which is consistent with the scalpel trajectory with a low resolution finite element grid. We model this realistic cutting as a deformation-fracture repeating process. In deformation stage, the object will deform along with the scalpel motion, while in the fracture stage cutting happens and a cutting surface will be generated from the scalpel trajectory. A delayed fracturing criteria is proposed to determine when and how the cutting fracture occurs and an influence domain adaptation method is employed to generate accurate cutting surface in both procedures of deformation and fracture. Experiments show that our method can realistically simulate volumetric cutting of deformable bodies and efficiently generate accurate cutting surface thus facilitating interactive applications.Item A Virtual Character Posing System based on Reconfigurable Tangible User Interfaces and Immersive Virtual Reality(The Eurographics Association, 2018) Cannavò, A.; Lamberti, F.; Livesu, Marco and Pintore, Gianni and Signoroni, AlbertoComputer animation and, particularly, virtual character animation, are very time consuming and skill-intensive tasks, which require animators to work with sophisticated user interfaces. Tangible user interfaces (TUIs) already proved to be capable of making character animation more intuitive, and possibly more efficient, by leveraging the affordances provided by physical props that mimic the structure of virtual counterparts. The main downside of existing TUI-based animation solutions is the reduced accuracy, which is due partly to the use of mechanical parts, partly to the fact that, despite the adoption of a 3D input, users still have to work with a 2D output (usually represented by one or more views displayed on a screen). However, output methods that are natively 3D, e.g., based on virtual reality (VR), have been already exploited in different ways within computer animation scenarios. By moving from the above considerations and by building upon an existing work, this paper proposes a VR-based character animation system that combines the advantages of TUIs with the improved spatial awareness, enhanced visualization and better control on the observation point in the virtual space ensured by immersive VR. Results of a user study with both skilled and unskilled users showed a marked preference for the devised system, which was judged as more intuitive than that in the reference work, and allowed users to pose a virtual character in a lower time and with a higher accuracy.Item Evaluating and Comparing Game-controller based Virtual Locomotion Techniques(The Eurographics Association, 2017) Sarupuri, Bhuvaneswari; Hoermann, Simon; Whitton, Mary C.; Lindeman, Robert W.; Robert W. Lindeman and Gerd Bruder and Daisuke IwaiThe incremental hardware costs of virtual locomotion are minimized when the technique uses interaction capabilities available in controllers and devices that are already part of the VE system, e.g., gamepads, keyboards, and multi-function controllers. We used a different locomotion technique for each of these three devices: gamepad thumb-stick (joystick walking), a customized hybrid keyboard for gaming (speedpad walking), and an innovative technique that uses the orientation and triggers of the HTC Vive controllers (TriggerWalking). We explored the efficacy of locomotion techniques using these three devices in a hide and seek task in an indoor environment. We measured task performance, simulator sickness, system usability, perceived workload, and preference. We found that users had a strong preference for TriggerWalking, which also had the least increase in simulator sickness, the highest performance score, and highest perceived usability. However, participants using TriggerWalking also had the most object and wall-collisions. Overall we found that TriggerWalking is an effective locomotion technique and that is has significant and important benefits. Future research will explore if TriggerWalking can be used with equal benefits in other virtual-environments, on different tasks, and types of movement.Item Real-Time Gaze Mapping in Virtual Environments(The Eurographics Association, 2019) Kraus, Matthias; Kilian, Timon Urs; Fuchs, Johannes; Madeiras Pereira, JoĂŁo and Raidou, Renata GeorgiaIn order to analyze an analyst's behavior in an immersive environment, his or her eye movements can be monitored using eye trackers. Hereby, points of individual interest can be objectively identified, for instance, to assess the usability and intuitiveness of a framework. However, this technique can be used not only as a post-event analysis tool but also to assist an ongoing exploration of a virtual environment. With this poster, we present a technique that allows a real-time gaze map creation which supports the immersed analyst by providing real-time feedback on the user's own activity. In our approach, all surfaces in the virtual environment are enwrapped with a mesh structure. The grid structure recognizes when a user drifts with his or her eyes above it and increments weights of activated node points. This allows highlighting areas that have been observed, but also those that have not been observed - also when they are occluded by other objects or surfaces. We tested our technique in a preliminary qualitative expert study and received helpful feedback for further improvements.Item A Novel Approach for Cooperative Motion Capture (COMOCAP)(The Eurographics Association, 2018) Welch, Gregory; Wang, Tianren; Bishop, Gary; Bruder, Gerd; Bruder, Gerd and Yoshimoto, Shunsuke and Cobb, SueConventional motion capture (MOCAP) systems, e.g., optical systems, typically perform well for one person, but less so for multiple people in close proximity. Measurement quality can decline with distance, and even drop out as source/sensor components are occluded by nearby people. Furthermore, conventional optical MOCAP systems estimate body posture using a global estimation approach employing cameras that are fixed in the environment, typically at a distance such that one person or object can easily occlude another, and the relative error between tracked objects in the scene can increase as they move farther from the cameras and/or closer to each other. Body-relative tracking approaches use body-worn sensors and/or sources to track limbs with respect to the head or torso, for example, taking advantage of the proximity of limbs to the body. We present a novel approach to MOCAP that combines and extends conventional global and body-relative approaches by distributing both sensing and active signaling over each person's body to facilitate body-relative (intra-user) MOCAP for one person and body-body (inter-user) MOCAP for multiple people, in an approach we call cooperative motion capture (COMOCAP). We support the validity of the approach with simulation results from a system comprised of acoustic transceivers (receiver-transmitter units) that provide inter-transceiver range measurements. Optical, magnetic, and other types of transceivers could also be used. Our simulations demonstrate the advantages of this approach to effectively improve accuracy and robustness to occlusions in situations of close proximity between multiple persons.Item Fast and Accurate Simulation of Gravitational Field of Irregular-shaped Bodies using Polydisperse Sphere Packings(The Eurographics Association, 2017) Srinivas, Abhishek; Weller, Rene; Zachmann, Gabriel; Robert W. Lindeman and Gerd Bruder and Daisuke IwaiCurrently, interest in space missions to small bodies (e.g., asteroids) is increasing, both scientifically and commercially. One of the important aspects of these missions is to test the navigation, guidance, and control algorithms. The most cost and time efficient way to do this is to simulate the missions in virtual testbeds. To do so, a physically-based simulation of the small bodies' physical properties is essential. One of the most important physical properties, especially for landing operations, is the gravitational field, which can be quite irregular, depending on the shape and mass distribution of the body. In this paper, we present a novel algorithm to simulate gravitational fields for small bodies like asteroids. The main idea is to represent the small body's mass by a polydisperse sphere packing. This allows for an easy and efficient parallelization. Our GPU-based implementation outperforms traditional methods by more than two orders of magnitude while achieving a similar accuracy.Item Visualising Dudsbury Hillfort: Using Immersive Virtual Reality to Engage the Public with Cultural Heritage(The Eurographics Association, 2018) John, David; Hurst, David; Cheetham, Paul; Manley, Harry; Sablatnig, Robert and Wimmer, MichaelWhilst computer visualisation is an established method of presenting cultural heritage, the use of game engines to provide a full immersive virtual reality experience is less well developed. This research documents the development of a visualisation of an Iron Age hillfort using Unreal Engine together with LiDAR terrain data to create a fully immersive experience for the virtual visitor. The visualisation was evaluated by 36 members of the public. The results show a high degree of satisfaction with the visualisation and agreement with the results of other studies demonstrating significant differences between those new to and those familiar with virtual reality applications. The conclusion is that in combination, game engines and LiDAR are effective tools for creating engaging virtual heritage visualisations.Item Ethical Considerations for the Use of Virtual Reality: An Evaluation of Practices in Academia and Industry(The Eurographics Association, 2017) Luro, Francisco Lopez; Prada, Diego Navarro; Sundstedt, Veronica; Robert W. Lindeman and Gerd Bruder and Daisuke IwaiThe following article offers a set of recommendations that are considered relevant for designing and executing experiences with Virtual Reality (VR) technology. It presents a brief review of the history and evolution of VR, along with the physiological issues related to its use. Additionally, typical practices in VR, used by both academia and industry are discussed and contrasted. These were further analysed from an ethical perspective, guided by legal and Corporate Social Responsibility (CSR) frameworks, to understand their motivation and goals, and the rights and responsibilities related to the exposure of research participants and final consumers to VR. Our results showed that there is a significant disparity between practices in academia and industry, and for industry specifically, there can be breaches of user protection regulations and poor ethical practices. The differences found are mainly in regards to the type of content presented, the overall setup of VR experiences, and the amount of information provided to participants or consumers respectively. To contribute to this issue, this study highlights some ethical aspects and also offers practical considerations that aim, not only to have more appropriate practices with VR in public spaces but also to motivate a discussion and reflection to ease the adoption of this technology in the consumer market.Item Projectional Radiography Simulator: an Interactive Teaching Tool(The Eurographics Association, 2019) Sujar, Aaron; Kelly, Graham; GarcĂa, Marcos; Vidal, Franck; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.Radiographers need to know a broad range of knowledge about X-ray radiography, which can be specific to each part of the body. Due to the harmfulness of the ionising radiation used, teaching and training using real patients is not ethical. Students have limited access to real X-ray rooms and anatomic phantoms during their studies. Books, and now web apps, containing a set of static pictures are then often used to illustrate clinical cases. In this study, we have built an Interactive X-ray Projectional Simulator using a deformation algorithm with a real-time X-ray image simulator. Users can load various anatomic models and the tool enables virtual model positioning in order to set a specific position and see the corresponding X-ray image. It allows teachers to simulate any particular X-ray projection in a lecturing environment without using real patients and avoiding any kind of radiation risk. This tool also allows the students to reproduce the important parameters of a real X-ray machine in a safe environment. We have performed a face and content validation in which our tool proves to be realistic (72% of the participants agreed that the simulations are visually realistic), useful (67%) and suitable (78%) for teaching X-ray radiography.