CEIG17

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https://diglib.eg.org/handle/10.2312/2631632

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Procedural Generation of Natural Environments with Restrictions
(The Eurographics Association, 2017) Gasch, Cristina; Chover, Miguel; Remolar, Inmaculada; Fco. Javier Melero and Nuria Pelechano
Natural 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.
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 Pelechano
The 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.
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 Pelechano
The 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.
Procedural Semantic Cities
(The Eurographics Association, 2017) Rogla, Otger; Pelechano, Nuria; Patow, Gustavo; Fco. Javier Melero and Nuria Pelechano
Procedural 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.
Dissipation Potentials for Yarn-Level Cloth
(The Eurographics Association, 2017) Sánchez-Banderas, Rosa M.; Otaduy, Miguel A.; Fco. Javier Melero and Nuria Pelechano
Damping 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.
Direct Volume Rendering of Stack-Based Terrains
(The Eurographics Association, 2017) Graciano, Alejandro; Rueda, Antonio J.; Feito, Francisco R.; Fco. Javier Melero and Nuria Pelechano
Traditionally, 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.
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 Pelechano
The 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.
An Interactive Tool for Modeling Ancient Masonry Buildings
(The Eurographics Association, 2017) Fita, Josep Lluis; Besuievsky, Gonzalo; Patow, Gustavo; Fco. Javier Melero and Nuria Pelechano
We present a new pipeline of an interactive tool that combines procedural modeling of ancient masonry buildings with structural simulation. The tool has been designed for taking an input geometry of an ancient building and re-meshing it into a suitable mesh with a low quad density. Then, it creates the brick outlines on the mesh and adds the brick volumes for structural simulation. The tool was designed and built on a set of off-the-shelf tools. We tested and demonstrated its viability by modeling of a Romanesque church based on a real one from the 11th century, such as the church of Santa Maria de Agullana.
3D GIS Based on WebGL for the Management of Underground Utilities
(The Eurographics Association, 2017) Jurado, Juan Manuel; Ortega, Lidia; Feito, Francisco R.; Fco. Javier Melero and Nuria Pelechano
This work summarizes a web application related to a research project about underground infrastructures. The aim is to visualize, analyse and manage all underground layers inside 3D urban environments. This is possible using WebGL to develop a web application which may be used from mobile devices. The study of terrain relief to calculate the depth of these infrestructures, the conversion of 2D data to 3D models, the definition of a spatial database and the use of virtual reality to visualize the resulting 3D scene make of this application a useful tool for utility companies dealing with underground infrastructures.
Transient Photon Beams
(The Eurographics Association, 2017) Marco, Julio; Jarosz, Wojciech; Gutierrez, Diego; Jarabo, Adrian; Fco. Javier Melero and Nuria Pelechano
Recent 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.
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 Pelechano
In 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.
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 Pelechano
This 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.
CEIG 2017 - Spanish Computer Graphics Conference: Frontmatter
(Eurographics Association, 2017) Melero, Fco. Javier; Pelechano, Nuria; Fco. Javier Melero and Nuria Pelechano
Google Tango Outdoors. Augmented Reality for Underground Infrastructures
(The Eurographics Association, 2017) Soria, Gregorio; Ortega, Lidia; Feito, Francisco R.; Fco. Javier Melero and Nuria Pelechano
Underground infrastructures, which support much of the services provided to citizens, have the peculiarity of not being directly visible. This leads to problems when making incursions for maintenance or creating new installations. In this framework, new technologies related to augmented reality are of special interest. This work presents a virtual reality application using Google Tango in order to visualize underground infrastructures in situ, allowing also free navigation. The system works on a clientserver architecture. The client obtains the location point as well as the orientation of the device. The server returns the virtual visualization of infrastructure elements and buildings from this viewpoint, which will be superimposed over the actual view. The server maintains a spatial database with topological characteristics that allow this and other modes of interaction, as well as some analytical capacity. This article focuses on aspects such as the transformation of input data, the data model, the different methodologies for rapid and effective positioning, as well as the usability of the application.
An Improved Parallel Technique for Neighbour Search on CUDA
(The Eurographics Association, 2017) Perea, Juan J.; Cordero, Juan M.; Fco. Javier Melero and Nuria Pelechano
In Computer Graphics is usual the modelling of dynamic systems through particles. The simulation of liquids, cloths, gas, smoke... are highlighted examples of that modelling. In this scope, is particularly relevant the procedure of neighbour particles searching, which represents a bottleneck in terms of computational cost. One of the most used searching techniques is the cell- based spatial division by cubes, where each cell is tagged by a hash value. Thus, all particles located into each cell have the same tag and are the candidate to be neighbours. The most useful feature of this technique is that it can be easily parallelized, what reduces the computational costs. Nevertheless, the parallelizing process has some drawbacks associated with data memory management. Also, during the process of neighbour search, it is necessary to trace into the adjacent cells to find neighbour particles, as a consequence, the computational cost is increased. To solve these shortcomings, we have developed a method that reduces the search space by considering the relative position of each particle in its own cell. This method, parallelized using CUDA, shows improvements in processing time and memory management over other ''standard'' spatial division techniques.
Physically Based Skeleton Tracking
(The Eurographics Association, 2017) López-Gandía, Axel; Susín, Antonio; Fco. Javier Melero and Nuria Pelechano
Skeleton tracking has multiple applications such as games, virtual reality, motion capture and more. One of the main challenges of pose detection is to be able to obtain the best possible quality with a cheap and easy-to-use device. In this work we propose a physically based method to detect errors and tracking issues which appear when we use low cost tracking devices such as Kinect. Therefore, we can correct the animation in order to obtain a smoother movement. We have implemented the Newton- Euler Algorithm, which allow us to compute the internal forces involved in a skeleton. In a common movement, forces are usually smooth without sudden variations. When the tracking yields poor results or invalid poses the internal forces become very large with a lot of variation. This allow us to detect when the tracking system fails and the animation needs to be inferred through different methods.
Transfer Learning for Illustration Classification
(The Eurographics Association, 2017) Lagunas, Manuel; Garces, Elena; Fco. Javier Melero and Nuria Pelechano
The field of image classification has shown an outstanding success thanks to the development of deep learning techniques. Despite the great performance obtained, most of the work has focused on natural images ignoring other domains like artistic depictions. In this paper, we use transfer learning techniques to propose a new classification network with better performance in illustration images. Starting from the deep convolutional network VGG19, pre-trained with natural images, we propose two novel models which learn object representations in the new domain. Our optimized network will learn new low-level features of the images (colours, edges, textures) while keeping the knowledge of the objects and shapes that it already learned from the ImageNet dataset. Thus, requiring much less data for the training. We propose a novel dataset of illustration images labelled by content where our optimized architecture achieves 86.61% of top-1 and 97.21% of top-5 precision. We additionally demonstrate that our model is still able to recognize objects in photographs.
Improved Intuitive Appearance Editing based on Soft PCA
(The Eurographics Association, 2017) Malpica, Sandra; Barrio, Miguel; Gutierrez, Diego; Serrano, Ana; Masia, Belen; Fco. Javier Melero and Nuria Pelechano
During the last few years, many different techniques for measuring material appearance have arisen. These advances have allowed the creation of large public datasets, and new methods for editing BRDFs of captured appearance have been proposed. However, these methods lack intuitiveness and are hard to use for novice users. In order to overcome these limitations, Serrano et al. [SGM 16] recently proposed an intuitive space for editing captured appearance. They make use of a representation of the BRDF based on a combination of principal components (PCA) to reduce dimensionality, and then map these components to perceptual attributes. This PCA representation is biased towards specular materials and fails to represent very diffuse BRDFs, therefore producing unpleasant artifacts when editing. In this paper, we build on top of their work and propose to use two separate PCA bases for representing specular and diffuse BRDFs, and map each of these bases to the perceptual attributes. This allows us to avoid artifacts when editing towards diffuse BRDFs. We then propose a new method for effectively navigate between both bases while editing based on a new measurement of the specularity of measured materials. Finally, we integrate our proposed method in an intuitive BRDF editing framework and show how some of the limitations of the previous model have been overcomed with our representation. Moreover, our new measure of specularity can be used on any measured BRDF, as it is not limited only to MERL BRDFs [MPBM03].
Tree Variations
(The Eurographics Association, 2017) Argudo, Oscar; Andújar, Carlos; Chica, Antoni; Fco. Javier Melero and Nuria Pelechano
The cost-effective generation of realistic vegetation is still a challenging topic in computer graphics. The simplest representation of a tree consists of a single texture-mapped billboard. Although a tree billboard does not support top views, this is the most common representation for still image generation in areas such as architecture rendering. In this paper we present a new approach to generate new tree models from a small collection of RGBA images of trees. Key ingredients of our method are the representation of the tree contour space with a small set of basis vectors, the automatic crown/trunk segmentation, and the continuous transfer of RGBA color from the exemplar images to the synthetic target. Our algorithm allows the efficient generation of an arbitrary number of tree variations and thus provides a fast solution to add variety among trees in outdoor scenes.
Fast Stippling based on Weighted Centroidal Voronoi Diagrams
(The Eurographics Association, 2017) Gómez, Eila; Méndez, Elías; Arroyo, Germán; Martín, Domingo; Fco. Javier Melero and Nuria Pelechano
Stippling is an artistic technique that has been used profusely in antiquity. One of the main problems is that it requires great skill and patience to achieve excellent results due to the large number of points that must be drawn even for small formats. The use of computers, in general, and GPUs, in particular, with their computing capacity, has allowed to overcome many of these limits. We present a real-time GPU stippling program that combines the advantages of positioning based on Weighted Centroidal Voronoi Diagrams and the realistic aspect of the scanned points.

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