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Item Downsampling and Storage of Pre-Computed Gradients for Volume Rendering(The Eurographics Association, 2017) Díaz-García, Jesús; Brunet, Pere; Navazo, Isabel; Vázquez, Pere-Pau; Fco. Javier Melero and Nuria PelechanoThe way in which gradients are computed in volume datasets influences both the quality of the shading and the performance obtained in rendering algorithms. In particular, the visualization of coarse datasets in multi-resolution representations is affected when gradients are evaluated on-the-fly in the shader code by accessing neighbouring positions. This is not only a costly computation that compromises the performance of the visualization process, but also one that provides gradients of low quality that do not resemble the originals as much as desired because of the new topology of downsampled datasets. An obvious solution is to pre-compute the gradients and store them. Unfortunately, this originates two problems: First, the downsampling process, that is also prone to generate artifacts. Second, the limited bit size of storage itself causes the gradients to loss precision. In order to solve these issues, we propose a downsampling filter for pre-computed gradients that provides improved gradients that better match the originals such that the aforementioned artifacts disappear. Secondly, to address the storage problem, we present a method for the efficient storage of gradient directions that is able to minimize the minimum angle achieved among all representable vectors in a space of 3 bytes. We also provide several examples that show the advantages of the proposed approaches.Item Procedural Generation of Natural Environments with Restrictions(The Eurographics Association, 2017) Gasch, Cristina; Chover, Miguel; Remolar, Inmaculada; Fco. Javier Melero and Nuria PelechanoNatural environments are a very important part of virtual worlds, both for video games and for simulators, but their manual creation can be a very expensive job. The procedural creation of these, allows to generate them easily and quickly, although there is no way to control the final result quickly and accurately. The purpose of this work is to present a new method of creation, that allows the procedural generation of a natural environment for applications such as rail shooter. The vegetation of the natural environment will be placed automatically along the area of the route. The method presented, is based on establishing on the ground a grid of points which are assigned a random function of probability of appearance of each species based on Perlin noise. In addition, the method draws from the heightmap the values necessary to distribute the natural elements. These values are combined along the distance of the route and next to a noise distribution, thus obtaining placement patterns that have a greater probability of occurrence in favorable points of the map and near the route. The results show that the method allows the procedural generation of these environments for any heightmap, also focusing the realism and the placement of the natural elements in the user visualization zone.Item Extending Industrial Digital Twins with Optical Object Tracking(The Eurographics Association, 2017) Tammaro, Antonio; Segura, Álvaro; Moreno, Aitor; Sánchez, Jairo R.; Fco. Javier Melero and Nuria PelechanoIn the last year, the concept of Industry 4.0 and smart factories has increasingly gained more importance. One of the central aspects of this innovation is the coupling of physical systems with a corresponding virtual representation, known as the Digital Twin. This technology enables new powerful applications, such as real-time production optimization or advanced cloud services. To ensure the real-virtual equivalence it is necessary to implement multimodal data acquisition frameworks for each production system using their sensing capabilities, as well as appropriate communication and control architectures. In this paper we extend the concept of the digital twin of a production system adding a virtual representation of its operational environment. In this way the paper describes a proof of concept using an industrial robot, where the objects inside its working volume are captured by an optical tracking system. Detected objects are added to the digital twin model of the cell along with the robot, having in this way a synchronized virtual representation of the complete system that is updated in real time. The paper describes this tracking system as well as the integration of the digital twin in a Web3D based virtual environment that can be accessed from any compatible devices such as PCs, tablets and smartphones.Item Unsupervised Framework for People Counting Using a Stereo-based Camera(The Eurographics Association, 2017) Negrillo, José; Feito, Francisco R.; Segura, Rafael J.; Ogayar, Carlos Javier; Fuertes, José Manuel; Lucena, Manuel; Fco. Javier Melero and Nuria PelechanoThe counting of people in a room or a building is a desirable feature in a Smart City environment. There are several hardware systems that simplify this process. However, those systems tend to be very intrusive. This paper proposes a framework for counting people using an efficient and multi-platform computer vision based system. This system is easily deployable in crowded places by using affordable components.Item Dissipation Potentials for Yarn-Level Cloth(The Eurographics Association, 2017) Sánchez-Banderas, Rosa M.; Otaduy, Miguel A.; Fco. Javier Melero and Nuria PelechanoDamping is a critical phenomenon in determining the dynamic behavior of animated objects. For yarn-level cloth models, setting the correct damping behavior is particularly complicated, because common damping models in computer graphics do not account for the mixed Eulerian-Lagrangian discretization of efficient yarn-level models. In this paper, we show how to derive a damping model for yarn-level cloth from dissipation potentials. We develop specific formulations for the deformation modes present in yarn-level cloth, circumventing various numerical difficulties. We show that the proposed model enables independent control of the damping behavior of each deformation mode, unlike other previous models.Item Direct Volume Rendering of Stack-Based Terrains(The Eurographics Association, 2017) Graciano, Alejandro; Rueda, Antonio J.; Feito, Francisco R.; Fco. Javier Melero and Nuria PelechanoTraditionally, the rendering of volumetric terrain data, as many other scientific 3D data, has been carried out performing direct volume rendering techniques on voxel-based representations. A main problem with this kind of representation is its large memory footprint. Several solutions have emerged in order to reduce the memory consumption and improve the rendering performance. An example of this is the hierarchical data structures for space division based on octrees. Although these representations have produced excellent outcomes, especially for binary datasets, their use in data containing internal structures and organized in a layered style, as in the case of surface-subsurface terrain, still leads to a high memory usage. In this paper, we propose the use of a compact stack-based representation for 3D terrain data, allowing a real-time rendering using classic volume rendering procedures. In contrast with previous work that used this representation as an assistant for rendering purposes, we suggest its use as main data structure maintaining the whole dataset in the GPU in a compact way. Furthermore, the implementation of some visual operations included in geoscientific applications such as borehole visualization, attenuation of material layers or cross sections has been carried out.Item Procedural Semantic Cities(The Eurographics Association, 2017) Rogla, Otger; Pelechano, Nuria; Patow, Gustavo; Fco. Javier Melero and Nuria PelechanoProcedural modeling of virtual cities has achieved high levels of realism with little effort from the user. One can rapidly obtain a large city using off-the-shelf software based on procedural techniques, such as the use of CGA. However in order to obtain realistic virtual cities it is necessary to include virtual humanoids that behave realistically adapting to such environment. The first step towards achieving this goal requires tagging the environment with semantics, which is a time consuming task usually done by hand. In this paper we propose a framework to rapidly generate virtual cities with semantics that can be used to drive the behavior of the virtual pedestrians. Ideally, the user would like to have some freedom between fully automatic generation and usage of pre-existing data. Existing data can be useful for two reasons: re-usability, and copying real cities fully or partly to develop virtual environments. In this paper we propose a framework to create such semantically augmented cities from either a fully procedural method, or using data from OpenStreetMap. Our framework has been integrated with Unreal Engine 4.Item A Curvature-based Method for Identifying the Contact Zone Between Bone Fragments: First Steps(The Eurographics Association, 2017) Jiménez-Pérez, J. Roberto; Paulano-Godino, Félix; Jiménez-Delgado, Juan J.; Fco. Javier Melero and Nuria PelechanoThe use of computer-assisted procedures before or during surgery provides orthopaedic specialists additional information that help them to reduce surgery time and to improve the understanding of the fracture peculiarities. In this context, the calculation of the fracture area is one of the main tasks in order to better comprehend the fracture. This paper presents the initial results of a method for the calculation of the contact zone between bone fragments by using a curvature-based approach. The method only considers cortical tissue, thus it is robust again the deformation or lack of trabecular tissue because of the fracture. In the case of simple fractures, the contact zone coincides with the entire fracture area. However, the calculation of the contact zone in complex fractures avoids calculating correspondences between fragments; hence the proposed method favours the use of puzzle solving methods in order to address the fracture reduction computation. Our proposal is able to overcome the initial limitations of curvature-based methods such as noise sensitivity, and shows a robust behaviour under circumstances of inexact segmentation or low precision.Item Fireman Rescue: A Serious Game for Fire Fighting Training(The Eurographics Association, 2017) Ríos, Alejandro; Bonet, Carles; Morales, J. L.; Alavedra, Axel; París, Alejandro; Guillén, Marc; Fco. Javier Melero and Nuria PelechanoThis paper introduces a Serious Game that will be used as a tool for training fire fighting students at the Public Security Institute of Catalonia. The game is played in a virtual environment free of real hazards and/or dangers with the consequent savings in material costs and supplies. The system exposes the student to different emergency situations that the he/she must solve using the professional firefighters tools and following the protocol of actual action provided in each case. It is also possible to interact with different virtual agents to delegate functions and to obtain information about the emergency to be solved. All actions carried out by the user are monitored by the system and are scored at the end of each game taking into account the order and time invested in performing them. In addition, feed-back is offered to improve the player's decision making in future matches.Item Transient Photon Beams(The Eurographics Association, 2017) Marco, Julio; Jarosz, Wojciech; Gutierrez, Diego; Jarabo, Adrian; Fco. Javier Melero and Nuria PelechanoRecent advances on transient imaging and their applications have opened the necessity of forward models that allow precise generation and analysis of time-resolved light transport data. However, traditional steady-state rendering techniques are not suitable for computing transient light transport due to the aggravation of the inherent Monte Carlo variance over time. These issues are specially problematic in participating media, which demand high number of samples to achieve noise-free solutions. We address this problem by presenting the first photon-based method for transient rendering of participating media that performs density estimations on time-resolved precomputed photon maps. We first introduce the transient integral form of the radiative transfer equation into the computer graphics community, including transient delays on the scattering events. Based on this formulation we leverage the high density and parameterized continuity provided by photon beams algorithms to present a new transient method that allows to significantly mitigate variance and efficiently render participating media effects in transient state.