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Item High Resolution Medical 3D Data Sets on Mobile Devices and WebGL(The Eurographics Association, 2012) Jimenez, Juan-Roberto; Noguera, Jose Maria; Isabel Navazo and Gustavo PatowNowadays, mobile devices and the web are being used to deliver 3D graphics to mass users. However, applications such as visualization of high resolution medical models are still impossible to handle in such platforms due to texture limitations, mainly the lack of 3D texture support. In this paper we propose a software architecture and a novel texture storage technique that overcome these limitations. In addition, our proposal allows us to adapt existing direct volume rendering techniques based on 3D textures to mobile devices and WebGL. Our experiments demonstrate the feasibility and validity of our proposal to render high resolution volumetric models on both platforms.Item Visual Language Generalization for Procedural Modeling of Buildings(The Eurographics Association, 2012) Barroso, Santiago; Patow, Gustavo; Isabel Navazo and Gustavo PatowProcedural modeling has become the accepted standard for the creation of detailed large scenes, in particular urban landscapes. With the introduction of visual languages there has been a huge leap forward in terms of usability, but there is still need of more sophisticated tools to simplify the development process. In this paper we present extensions to the visual modeling of procedural buildings, which adapt concepts from general purpose programming languages, with the objective of providing higher descriptive power. In particular, we present the concepts of visual modules, parameter linking and the possibility to seamlessly add abstract parameter templates to the designer visual toolbox. We base our demonstrations on a new visual language created for volume-based models like historic architectonic structures (aqueducts, churches, cathedrals, etc.), which cannot be modeled as 2D facades because of the intrinsic volumetric structure of these construction (e.g. vaults or arches).Item Generating Coherent Ray Directions in Path Tracing(The Eurographics Association, 2012) Torres, Roberto; MartÃn, Pedro J.; Gavilanes, Antonio; Isabel Navazo and Gustavo PatowThe quality of the images produced by a global illumination rendering engine is highly connected to the number of paths that are randomly generated from the camera to the light sources. Graphics Processing Units (GPUs) have been used to implement renderers by typically binding each thread to a ray. Nevertheless, this purely random generation does not fit well on the architecture of current GPUs, due to their SIMD nature. We modify the way paths are extended in order to take the most of GPUs. The arrangement of rays is split into groups of contiguous rays. The hemisphere on each intersection point is divided into spherical patches, and the same patch is chosen for all the rays in the group. The next direction for each path will be randomly chosen on that patch. Thus, if the intersection points of a group are near, the new rays spawned will be similar. We have implemented different configurations of this idea on a path tracer in CUDA and they have been experimentally tested on usual scenes. In the same amount of time, most of our algorithms complete more paths and, therefore, they produce images of higher quality than those obtained by the purely random generation.Item Differential Ray Marching(The Eurographics Association, 2012) Muñoz, Adolfo; Isabel Navazo and Gustavo PatowSeveral participating media rendering algorithms are based on ray marching: they integrate the variations of radiance along the volume covered by the participating media by splitting the path of light into segments and sampling light contribution at each of those segments. This paper revisits the concept of ray marching not as an integration technique, but as the application of a numerical method to solve an initial value differential equation. We present how to apply different numerical methods as ray marching techniques, analyze a wide range of them and study their applicability under different scenarios. Furthermore, we show how each of them improves over traditional ray marching. Any participating media rendering algorithm that is based on ray marching will benefit from the application of our technique by reducing the number of needed samples (and therefore, rendering time) and/or increasing accuracy.Item A Procedural Modeling System for the Creation of Huge Models(The Eurographics Association, 2012) Cubero, Francisco; Mas, Albert; Patow, Gustavo; Isabel Navazo and Gustavo PatowThis paper presents a new general purpose procedural geometrical modeling system. It is focused on providing flexibility, modularity and scalability. Furthermore, it is taylored to manage huge geometric models, with millions of polygons. An out-of-core memory management system assures that any scene size can be generated during the modeling evolution. This generation is performed by a set of rules and operations on geometrical objects, organized as a directed acyclic graph.Item More Stable SPH-based Fluid Simulation(The Eurographics Association, 2012) Perea, Juan J.; Cordero, Juan M.; Isabel Navazo and Gustavo PatowThe simulation of fluid is a field largely discussed, from the viewpoint of engineering, in the so-called computational fluid dynamics (CFD). A problem that occurs repeatedly in the literature of CFD is the stability of the simulation. One of the elements that introduce instability in any CFD model is the temporal integration method. Among the most commonly used CFD techniques, both in the field of engineering and in the computer graphics, is SPH, which is particularly relevant to its computational simplicity. However, this technique adds stability problems due to the treatment of viscous and pressure terms arising from the formulation of Navier'Stokes. SPH also introduces greater instability by the need to use interpolation functions appropriate to the phenomena that occur in fluid dynamics. We present solutions to these four problems of inestability mentioned: treatment of the terms of pressure and viscosity that appear in the Navier'Stokes, the formulation of the characteristic interpolation function of SPH and treatment of temporal integration.Item A Survey on Development Tools for Mobile Augmented Reality(The Eurographics Association, 2012) Rovelo, Gustavo; Abad, Francisco; Camahort, Emilio; Isabel Navazo and Gustavo PatowAugmented Reality (AR) applications have become more popular beyond the research laboratory due to recent technological breakthroughs in computer hardware and mobile devices. Users are starting to interact with virtual content mixed with real environments at their offices, homes, and schools using their mobile phones. For this growing market, developers have first to decide the platform in which they will develop the application (e.g. Apple iOS or Android). Then they must decide whether start writing the application from scratch using only platform native tools, or using one of the available Software Development Kits (SDKs), or using high-level authoring tools for the chosen platform. Besides, developers have to face different AR related issues according to the application's requirements: markers, barcodes or general image tracking, geolocation, efficient rendering of 3D objects, and designing a robust GUI for the target devices. To help developers and researchers to start writing mobile AR applications, this survey identifies the main features of several freeware and commercial SDKs and authoring tools.Item Bringing Direct Local Control to Interactive Visual Editing of Procedural Buildings(The Eurographics Association, 2012) Riu, Adria; Patow, Gustavo; Isabel Navazo and Gustavo PatowThis paper presents a new system to add direct and persistent local control to the visual editing of rules for procedural buildings, avoiding a combinatorial explosion of grammar rules. In this paper we follow the ideas initially proposed by Lipp and co-workers [LWW08]. For this, we have added a few simple new commands, which are added to the artist-provided ruleset in a way completely transparent to the user. The end-user selects the primitives/assets to modify, and the system automatically incorporates these modifications into the ruleset. This change is performed using graph-rewriting techniques, which are both simple to define and control, but also very powerful and practical for these situations.