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Item GreenArt: A Tool for Non-Photorealistic Rendering of Plants and Trees(Eurographics Association, 2003) Campos, C.; Quirós, R.; Huerta, J.; Camahort, E.; Lluch, J.; Vivo, R.Plant and tree rendering is critical to many computer graphics applications, like interactive walkthroughs, architectural presentations, entertaintment and computer games. Current research focuses on realistic modeling and rendering of plants and trees. In this paper, however, we focus on non-photorealistic rendering of these models. We introduce GreenArt, a tool for a modeling and rendering non-photorealistic plants and trees. We present GreenArt’s functionality and capabilities and we show some examples of scenes generated using the system.Item Large XML Document Manager and Visualizer(Eurographics Association, 2003) Merienne, J. P.; Jacquemin, C.This work presents an interactive Graphical User Interface used to display and manipulate collection of large XML documents. It relies on a geometrical model that combines hierarchical and sequential representations. In this interface, XML structures are displayed on an inclined plane in a 3D environment. This interface provides users with a visualization that speeds up searches in collection of documents through simple interaction techniques. Document browsing is facilitated through display space optimization and direct manipulation of document structures. Besides, this approach tries to take advantage of 3D by engaging human 3D spatial cognitive capabilities while using 2D interaction to not disrupt user's habits. A user evaluation for document access is reported that shows that our interface tends to be faster than 2D interface in data searching while taking advantage of the user's natural attraction to 3D interface.Item Fast Marching farthest point sampling(Eurographics Association, 2003) Moenning, Carsten; Dodgson, Neil A.We introduce the Fast Marching farthest point sampling (FastFPS) approach for the progressive sampling of planar domains and curved manifolds in triangulated, point cloud or implicit form. By using Fast Marching methods2, 3, 6 for the incremental computation of distance maps across the sampling domain, we obtain a farthest point sampling technique superior to earlier point sampling principles in two important respects. Firstly, our method performs equally well in both the uniform and the adaptive case. Secondly, the algorithm is applicable to both images and higher dimensional surfaces in triangulated, point cloud or implicit form. This paper presents the methods underlying the algorithm and gives examples for the processing of images and triangulated surfaces. A companion report4 provides details regarding the application of the FastFPS algorithm to point clouds and implicit surfaces.Item Persepolis: Recovering history with a handheld camera(Eurographics Association, 2003) Sainz, M.; Susin, A.; Cervantes, A.; Bagherzadeh, N.In this paper we present new improvements to our novel pipeline for image based modeling of objects using a camcorder. Our system takes an uncalibrated sequence of images recorded around a scene, it automatically recovers the underlying 3D structure and camera path and then a volumetric scene reconstruction is performed using a hardware accelerated voxel carving approach. Finally a triangular mesh is obtained and the available information from the images is combined to generate a full 3D photo-realistic reconstruction. As an application, we use this system to reconstruct parts of the archeological site of Persepolis (Iran).Item Real time positioning system based on active stereo and facial features identification(Eurographics Association, 2003) Frosio, Iuri; Lanzarotti, Raffaella; Campadelli, Paola; Ferrigno, Giancarlo; Borghese, N. AlbertoWe propose a new system for patient’s head positioning for radiology and radiotherapy. The system is constituted of two low-cost digital cameras and a digital projector. As a first step a bright pattern is projected onto the subject’s face and a 3D model of the face is reconstructed in real-time. The pattern guides the selection of feature regions of the face: the eyes, the lips and the nose. Inside these regions features are recognized using image processing techniques; 3D many-fold analysis can improve this stage. From these features the position and orientation over time of the face can be determined.Item Polygon-Polygon Collision Detection in 2D(Eurographics Association, 2003) Jiménez Delgado, Juan J.; Segura Sánchez, Rafael J.; Feito Higueruela, Francisco R.Collision detection between moving objects is an open question which raises major problems concerning its algorithmic complexity. In this paper we present a polygon collision detection algorithm which uses polygon decomposition through triangle coverings and polygon influence areas (implemented by signs of barycentric coordinates). By using influence areas and the temporal and spatial coherence property, the amount of time needed to detect a collision between objects is reduced. By means of these techniques, a valid representation for any kind of polygon is obtained, whether concave or convex, manifold or nonmanifold, with or without holes, as well as a collision detection algorithm for this type of figures. This detection algorithm has been compared with the well-known PIVOT2D1 one and better results have been achieved in most situations. This improvement together with its possible extension to 3D makes it an attractive method because pre-processing of the polygons is no longer necessary. Besides, since this method uses sign operations, it proves to be a simple, more efficient and robust method.Item Interactive demo: OpenGLfly, version Euskadi(Eurographics Association, 2003) Gómez de Segura, José Daniel; Fernández, Borja; Peral, Rosa; López, Susana; Ibáñez, EduardoThis paper describes the demo associated to one of our projects, which is currently under development. The version presented can be considered as a large terrain simulation over the Basque Country area (North of Spain), with real imagery, georeferenced information and a user friendly and interactive interface. The main goal is to demonstrate the applications of virtual reality techniques to fields such as virtual tourism, low cost simulators or edutainment. The requirements of the demo are low enough for it to be run in a home PC with a middle range graphics accelerator card. Currently, there are some OpenGL optimisations specific to NVIDIA chipsets and consequently this platform has a slight advantage in terms of performance.Item VR Game Interfaces for Interaction onto 3D Display(Eurographics Association, 2003) Choi, Jeong-Dan; Jang, Byung-Tae; Hwang, Chi-JeongThis paper describes the VR game interfaces for interaction onto 3D display. The challenge we are interested in is how to build and use a low cost 3D display that satisfies semi-immersive requirements and how to coordinate it with interactions into the immersive VR game environments. So, the objective of our display system is to produce a viewer-oriented, stereoscopic display; each of the user’s eyes should see an image correctly rendered from that eye’s position through the window of the displays. To accomplish this project, we concrete a projection-based multiple window rendering system on passive 3D stereo display, synchronization multichannel system for wide field of view on different PCs, and game user interactions using real-time virtual character animations. Our preliminary results are well suited for VR Safari as game contents with surround displays running on a PC clusters.Item Predictive fixed-frame rate tessellation of NURBS surfaces(Eurographics Association, 2003) Sanchez, H.; Moreno, A.; Garcia-Alonso, A.In this work we propose a predictive fixed-frame rate scheme that shows how to control the visualization frame rate using uniform dynamic tessellation. Similar to previous works5; 6, tessellation quality criteria is based on the triangle edge length.Item Certosa virtual museum: a dynamic multilevel desktop VR application(Eurographics Association, 2003) Calori, L.; Diamanti, T.; Guidazzoli, A.; Liguori, M. C.; Mauri, M. A.; Valentini, L.Starting from the exigencies of restoration, safeguard and promotion set by Bologna City Council for its Museum of the Certosa Cemetery, a multilevel application has been developed. Its main features are dynamic generation of models, interaction with objects, link to relational multimedia database, DTM and a friendly, computer games like interface. The outcome is a flexible product, both from a technological point of view – it can be experienced on low cost platforms as well as in HI End systems - and for the possible kind of fruition, that can involve several different groups of users.Item Parametric Foveation for Progressive Texture and Model Transmission(Eurographics Association, 2003) Cheng, Irene; Basu, Anup; Pan, YixinSpatially varying sensing (foveation) has been used in many different areas of Computer Vision, such as image compression and video teleconferencing and in perceptually driven Level of Detail (LOD) representations in graphics. In this work, we show that foveation is advantageous for interactive mesh and texture transmission in online 3D applications. Unlike traditional mesh representations where all 3D vertices need to be transmitted, we only need to transmit a collection of points-of-interest (foveae) and information on only one (rather than three) axis. Thereby, we can achieve a threefold reduction in the amount of data that needs to be transmitted to represent a new 3D model. Our research differs from level of detail (LOD) based approaches using perceptually driven simplification in that (i) the mesh and texture resolutions vary smoothly and continuously in our approach compared to distinct levels of details in adjoining regions in other foveated or multiresolution LOD based methods; and (ii) the approach works for an integrated foveated texture and mesh representation. The current implementation extends our past research in image and video compression [1] and is restricted to regular grid mesh representation produced by 3D scanners.Item Resampling structured grids into regular ones(Eurographics Association, 2003) Dimitrov, Leonid I.; Kolcun, Aleksej; Sramek, MilosStructured grids and some of their applications in natural sciences are discussed. The problem of their visualization and quantitative evaluation is considered and possible ways for its solution sketched. Resampling a structured grid onto a regular one is one of the possible solutions offering the additional benefit of opening up more possibilities for qualification and quantification, too. Some methods for achieving this goal are presented, their advantages and disadvantages compared, and preliminary results from the application of our own method shown.Item Pedagogic discrete visualization of electromagnetic waves(Eurographics Association, 2003) Mora, F.; Ruillet, G.; Andres, E.; Vauzelle, R.A dynamic electromagnetic wave propagation visualization tool is presented in this paper. It can simulate wave reflection and diffraction in 2D. It allows to visualize the electric field magnitude. The original approach is based on discrete analytical geometry allowing a dynamic visualization of the wave propagation contrary to existing models. We use it for the moment as pedagogic tool for the understanding of this complex phenomenon.Item Pen and Ink Pictures from Gray-Scale Photographs(Eurographics Association, 2003) Arroyo, G.; Martín, D.A new method for producing pen and ink pictures from gray-scale photographs is introduced in this article. It is based on path-finding and reconstruction of strokes. First we apply filters to extract contours from photographs which are converted to strokes, then we show how to modify these strokes in the same way an artist could do it. The strokes are not pixel-based but bspline curves, which are rendered simuling different kinds of brushes and papers.Item 3deSoundBox – a Scalable, Platform-Independent 3D Sound System for Virtual and Augmented Reality Applications(Eurographics Association, 2003) Stampfl, PhilippSound is one of the most important components in animations, presentations and especially immersive environments. Many aspects are recognized more intuitively when sound supports vision and it is easier to follow a story and to believe in a virtual world of illusion. The 3deSoundBox was designed to provide this important acoustic component for such kind of 3D applications in an easy and intuitive way. It is scalable, platform-independent, has an easy to use interface and offers a lot of new possibilities in the field of virtual and augmented reality applications. The 3deSoundBox system can drive any number of speakers and works with any application on any platform with the same range of service. Once programmed, an application can easily take advantage of these features, as it will work on any sound-system with any number of speakers without requiring any changes, due to the scalable architecture of the system.Item Multi-resolution modelling of terrains by using non restricted quadtree triangulation(Eurographics Association, 2003) Aguilera, A.; Torres, J. C.; Feito, F.The interactive visualization of terrains requires the processing of a high amount of data in real time, usually it is not possible to work with all of them on main in memory. In this work we present, a method which solves the above problem by means of using spatial indices (quadtree). For that, the terrains are divided into square cells, each of them having a quadtree, which will only be refined up to a the detail level depending on the observer position. With this, allaus to reduce the time used for terrains visualization.Item Anisotropic Participating Media at Near Interactive Rates(Eurographics Association, 2003) Jimenez, Juan-Roberto; Pueyo, XavierThis article presents an algorithm for the realistic simulation, at near interactive rates, of globally illuminated scenes including participating media, isotropic and anisotropic. The proposed algorithm is divided in three phases: particle tracing, reconstruction and rendering. The particle tracing phase is based on the Monte Carlo light tracing. The goal of this phase is to deliver the light energy from the sources, over the scene’s object. In the reconstruction phase the algorithm derives one texture for each object in the scene, 2D textures for surfaces and 3D textures for participating media. Each texel represents the outgoing radiance, in a given direction, from a region of the object. The method uses density estimation techniques to compute the textures. In the final phase, the algorithm renders the textures using hardware graphics capabilities.Item A Spatial Representation for Ray-Scene Intersection Test Improvement in Complex Scenes(Eurographics Association, 2003) Revelles, J.; Aguilera, N.; Aguado, J.; Lastra, M.; Garcia, R.; Montes, R.We present a spatial representation based on a hierarchical structure using the well-known spatial indexing structure called octree. There are very useful spatial representations for scenes whose objects can be distributed in clusters and here we present a new one. In order to prove its benefits, several results are shown in scenes using a photom tracing algorithm to compute the global illumination based on photon map. These results show that the hierarchy of octrees becomes a good choice to improve the performance when compare to other strategies such as octrees and hierarchy of uniform grids3.Item Virtual Modelling(Eurographics Association, 2003) Kiss, Szilárd; Nijholt, Anton; Zwiers, JobWe concentrate our efforts on building virtual modelling environments where the content creator uses controls (widgets) as an interactive adjustment modality for the properties of the edited objects. Besides the advantage of being an on-line modelling approach (visualised just like any other on-line VRML content), our approach provides also instant visualisation and an intuitive, graphical editing modality. Although visual modelling environments are more powerful in content creation than a text editor, our aim is to include certain domain knowledge to extend their capabilities. Our most recent system is a 3D character modeller capable of handling H-anim or other types of hierarchies (based also on H-anim components) and the geometry attached to them. The modelling is based on the properties of regular grid geometries, on H-anim hierarchies and where applicable, on 3D character symmetry. The novelty of our approach consists of 1) natural graphics components; 2) integrating the interface elements into the virtual environment itself; 3) rule based modelling of 3D characters; 4) on-line modelling.Item Curve Synthesis from Learned Refinement Models(Eurographics Association, 2003) Simhon, Saul; Dudek, GregoryWe present a method for generating refined 2D illustrations from hand drawn outlines consisting of only curve strokes. The system controllably synthesizes novel illustrations by augmenting the hand drawn curves’ shape, thickness, color and surrounding texture. These refinements are learned from a training ensemble. Users can select several examples that depict the desired idealized look and train the system for that type of refinement. Further, given several types of refinements, our system automatically recognizes the curve and applies the appropriate refinement. Recognition is accomplished by evaluating the likelihood the curve belongs to a particular class based on both its shape and context in the illustration.