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Item Accelerating Surface Tension Calculation in SPH via Particle Classification and Monte Carlo Integration(The Eurographics Association, 2019) Zorrilla, Fernando; Sappl, Johannes; Rauch, Wolfgang; Harders, Matthias; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.Surface tension has a strong influence on the shape of fluid interfaces. We propose a method to calculate the corresponding forces efficiently. In contrast to several previous approaches, we discriminate to this end between surface and non-surface SPH particles. Our method effectively smooths the fluid interface, minimizing its curvature. We make use of an approach inspired by Monte Carlo integration to estimate local normals as well as curvatures, based on which the force can be calculated. The technique is applicable, but not limited to 2D and 3D simulations, and can be coupled with any common SPH formulation. It outperforms prior approaches with regard to total computation time per time step, while being stable and avoiding artifacts.Item Deep Terrain Expansion: Terrain Texture Synthesis with Deep Learning(The Eurographics Association, 2019) Toulatzis, Vasilis; Fudos, Ioannis; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.In real-world applications terrains play a cardinal role in the field of games and geospatial applications such as Geographic Information Systems (GIS). The textures of a terrain are essential for creating virtual photorealistic environments for users. In many cases, the entire texture of a region is not available in high resolution or is much smaller than the required texture to cover a terrain. Tiling of a texture across a terrain or using an enlarged version of it usually fails to provide an acceptable photorealistic result. Consequently, high quality texture synthesis is a central issue in such settings. In this paper, we explore a novel methodology that extends previous work providing both synthesis and expansion/shrinkage of a texture.Item Projectional Radiography Simulator: an Interactive Teaching Tool(The Eurographics Association, 2019) Sujar, Aaron; Kelly, Graham; GarcÃa, 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.Item Optimising Underwater Environments for Mobile VR(The Eurographics Association, 2019) Cenydd, Llyr ap; Headleand, Christopher; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.Mobile Virtual Reality (VR) has advanced considerably in the last few years, driven by advances in smartphone technology. There are now a number of commercial offerings available, from smartphone powered headsets to standalone units with full positional tracking. Similarly best practices in VR have matured quickly, facilitating comfortable and immersive VR experiences. There remains however many optimisation challenges when working with these devices, as while the need to render at high frame rates is universal, the hardware is limited by both computational power and battery capacity. There is also often a requirement that apps run smoothly across a wide variety of headsets. In this paper, we describe lessons learned in rendering and optimising underwater environments for mobile VR, based on our experience developing the popular aquatic safari application 'Ocean Rift'. We start by analyzing essential best practices for mobile app development, before describing low-cost techniques for creating immersive underwater environments. While some techniques discussed are universal to modern mobile VR development, we also consider issues that are unique to underwater applications.Item CGVC 2019: Frontmatter(Eurographics Association, 2019) Vidal, Franck; Tam, Gary K. L.; Roberts, Jonathan C.; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.Item Deformed Reality(The Eurographics Association, 2019) Petit, Antoine; Haouchine, Nazim; Roy, Frederick; Goldman, Daniel B.; Cotin, Stephane; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.We present Deformed Reality, a new way of interacting with an augmented reality environment by manipulating 3D objects in an intuitive and physically-consistent manner. Using the core principle of augmented reality to estimate rigid pose over time, our method makes it possible for the user to deform the targeted object while it is being rendered with its natural texture, giving the sense of a interactive scene editing. Our framework follows a computationally efficient pipeline that uses a proxy CAD model for both pose computation, physically-based manipulations and scene appearance estimation. The final composition is built upon a continuous image completion and re-texturing process to preserve visual consistency. The presented results show that our method can open new ways of using augmented reality by not only augmenting the environment but also interacting with objects intuitively.Item Colour Processing in Adversarial Attacks on Face Liveness Systems(The Eurographics Association, 2019) Abduh, Latifah; Ivrissimtzis, Ioannis; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.In the context of face recognition systems, liveness test is a binary classification task aiming at distinguishing between input images that come from real people's faces and input images that come from photos or videos of those faces, and presented to the system's camera by an attacker. In this paper, we train the state-of-the-art, general purpose deep neural network ResNet for liveness testing, and measure the effect on its performance of adversarial attacks based on the manipulation of the saturation component of the imposter images. Our findings suggest that higher saturation values in the imposter images lead to a decrease in the network's performance. Next, we study the relationship between the proposed adversarial attacks and corresponding direct presentation attacks. Initial results on a small dataset of processed images which are then printed on paper or displayed on an LCD or a mobile phone screen, show that higher saturation values lead to higher values in the network's loss function, indicating that these colour manipulation techniques can indeed be converted into enhanced presentation attacks.Item Controlling 3D Visualisations with Multiple Degrees of Freedom(The Eurographics Association, 2019) Sandoval, Mario; Morris, Tim; Turner, Martin; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.In this paper, the two major components of a new multi-layer framework ideal for two-handed interaction in desktop virtual environments called Library for Interactive Settings of User-Mode (LISU) are explained. In addition, we evaluate LISU performance with a group of participants and we report some of our initial results by giving an analysis of user experiences, and interaction speed.Item Fast and Efficient Nearest Neighbor Search for Particle Simulations(The Eurographics Association, 2019) Gross, Julian; Köster, Marcel; Krüger, Antonio; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.One of the fundamental algorithms in particle simulations is the identification and iteration over nearest neighbors of every particle. Well-known examples are SPH or PBD simulations that compute forces and particle-position updates in every simulation step. In order to find nearest neighbors for all particles, hash-based, grid-based or tree-based approaches have been developed in the past. The two most prominent and fastest algorithms use virtual and explicitly allocated uniform grids to achieve high performance on Graphics Processing Units (GPUs). However, they have disadvantages with numerous particle simulation domains, either in terms of run time or memory consumption. We present a novel algorithm that can be applied to large simulation domains that significantly reduces memory consumption using a shared-memory based neighbor search. Furthermore, we achieve high-performance on our evaluation scenarios that often outperforms existing state-of-the-art methods.Item A Mesh Correspondence Approach for Efficient Animation Transfer(The Eurographics Association, 2019) Moutafidou, Anastasia; Fudos, Ioannis; Vidal, Franck P. and Tam, Gary K. L. and Roberts, Jonathan C.Animating a novel character not only needs a lot of effort and time but also requires the intervention of an experienced user. Moreover, the traditional animation pipeline for a set of characters can be a tedious and cumbersome process which often needs to be repeated several times to correct artifacts. We propose a user-friendly, semi-automated efficient method which is realized in two phases: (i) mesh correspondence, and (ii) skeleton and skinning transfer. We have developed a software tool for realizing the entire process without the need of third party software. We have improved the efficiency of the entire animation transfer process. To substantiate this, we provide a comparative performance evaluation with previous competent approaches.