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Now showing 1 - 10 of 238
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    Modelling and Rendering Graphics Scenes Composed of Multiple Volumetric Datasets
    (Blackwell Publishers Ltd and the Eurographics Association, 1999) Leu, Adrian; Chen, Min
    This paper presents a method for modelling graphics scenes consisting of multiple volumetric objects. A two-level hierarchical representation is employed, which enables the reduction of the overall storage consumption as well as rendering time. With this approach, different objects can be derived from the same volumetric dataset, and 2D images can be trivially integrated into a scene. The paper also describes an efficient algorithm for rendering such scenes on ordinary workstations, and addresses issues concerning memory requirements and disk swapping.
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    ve99
    (1999)
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    Virtual Dunhuang Art Cave: A Cave within a CAVE
    (Blackwell Publishers Ltd and the Eurographics Association, 1999) Lutz, B.; Weintke, M.
    Virtual Reality can present historical places in a three-dimensional and interactive way, giving visitors a photorealistic impression of objects. Not only existing scenarios can be shown, but VR can also be used to rebuild scenarios that were damaged or destroyed a long time ago, giving new life to the cultural heritage. We used Virtual Reality to present the Mogao Grottos in Dunhuang. This cave site is one of the most important cultural and religious places by the ancient Silk Road. The presentation is to give visitors the impression of visiting the cave site and provide information about the caves, paintings and statues in an interesting way. To achieve this, we developed a new, intuitive interaction paradigm, which enables the user to explore the caves. To give observers a photorealistic impression of the caves and to create a feeling of immersion, innovative rendering techniques were integrated.The resulting presentation combines Virtual Reality and archaeology to give tourists a realistic experience of this cave site and to support scientists in their research work.
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    WebTalk: a 3D collaborative environment to access the Web
    (Eurographics Association, 1999) Paolini, P.; Barbieri, T.; Loiudice, P.; Alonzo, F.; Arru, M.; Zanti, M.; Gaia, G.
    The notion of cooperative visit and interaction within a web site, both at 2D and 3D level, could add decisive motivation to pursue exploitation of the third dimension in networked environments. A prototype developed at the HOC laboratory in Politecnico of Milan, WEBTALK, allows development of custom 3D environments in which actions and situations can be shared throughout a network. The current prototype makes use of standard web-based Internet/Intranet technology: it is composed of a VRML (Virtual Reality Modeling Language) graphical engine and a Java-based TCP/IP (the Internet Protocol) communication layer. The technique has proven itself successful and has given rise to several interesting applications, such as the creation of Virtual 3D Museum Spaces at the National Science Museum (www.museoscienza.org), in which visitors can visit the museum interacting with the exhibits themselves and sharing their experiences with other visitors - even joining a guided tour with the virtual museum guide. A new prototype will make use of a completely Java-based environment, using Sun’s Java 2 and Java 3D. The new WEBTALK will stress even further the issues of third party external authoring of virtual worlds and of cooperation patterns within the shared environments, with a distinction between shared object geometries, shared object behaviors, shared object data (stored in an on-line DBMS), and cooperation metaphors within the virtual world. Linking to 2D-based web sites resources will lead cooperation patterns to be extended also to regular web-space.
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    Improved Laplacian Smoothing of Noisy Surface Meshes
    (Blackwell Publishers Ltd and the Eurographics Association, 1999) Vollmer, J.; Mencl, R.; Muller, H.
    This paper presents a technique for smoothing polygonal surface meshes that avoids the well-known problem of deformation and shrinkage caused by many smoothing methods, like e.g. the Laplacian algorithm. The basic idea is to push the vertices of the smoothed mesh back towards their previous locations. This technique can be also used in order to smooth unstructured point sets, by reconstructing a surface mesh to which the smoothing technique is applied. The key observation is that a surface mesh which is not necessarily topologically correct, but which can efficiently be reconstructed, is sufficient for that purpose.
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    Texturing 3D Models of Real World Objects from Multiple Unregistered Photographic Views
    (Blackwell Publishers Ltd and the Eurographics Association, 1999) Neugebauer, Peter J.; Klein, Konrad
    As the efficiency of computer graphic rendering methods is increasing, generating realistic models is now becoming a limiting factor. In this paper we present a new technique to enhance already existing geometry models of real world objects with textures reconstructed from a sparse set of unregistered still photographs. The aim of the proposed technique is the generation of nearly photo-realistic models of arbitrarily shaped objects with minimal effort. In our approach, we require neither a prior calibration of the camera nor a high precision of the user's interaction. Two main problems have to be addressed of which the first is the recovery of the unknown positions and parameters of the camera. An initial estimate of the orientation is calculated from interactively selected point correspondences. Subsequently, the unknown parameters are accurately calculated by minimising a blend of objective functions in a 3D-2D projective registration approach. The key point of the proposed method of registration is a novel filtering approach which utilises the spatial information provided by the geometry model. Second, the individual images have to be combined yielding a set of consistent texture maps. We present a robust method to recover the texture from the photographs thereby preserving high spatial frequencies and eliminating artifacts, particularly specular highlights. Parts of the object not seen in any of the photographs are interpolated in the textured model. Results are shown for three complex example objects with different materials and numerous self-occlusions.
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    mm99
    (1999)
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    Approximating the Location of Integrand Discontinuities for Penumbral Illumination with Area Light Sources
    (The Eurographics Association, 1999) Ouellette, Marc J.; Fiume, Eugene; Dani Lischinski and Greg Ward Larson
    The problem of computing soft shadows with area light sources has received considerable attention in computer graphics. In part, this is a difficult problem because the integral that defines the radiance at a point must take into account the visibility function. Most of the solutions proposed have been limited to polygonal environments, and require a full visibility determination preprocessing step. The result is typically a partitioning of the environment into regions that have a similar view of the light source. We propose a new approach that can be successfully applied to arbitrary environments. The approach is based on the observation that, in the presence of occluders, the primary difficulty in computing the integral that defines the contribution of an area light source, is that of determining the visible domain of the integrand. We extend a recent shadow algorithm for linear light sources in order to calculate a polygonal approximation to this visible domain. We demonstrate for an important class of shadowing problems, and in particular, for convex occluders, that the shape of the visible domain only needs to be roughly approximated by a polygonal boundary. We then use this boundary to subdivide an area light source into a small number of triangles that can be integrated efficiently using either a deterministic solution, or a low degree numerical cubature.
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    Efficiently Rendering Large Volume Data Using Texture Mapping Hardware
    (Springer and The Eurographics Association, 1999) Tong, Xin; Wang, Wenping; Tsang, Waiwan; Tang, Zesheng; Gröller, E., Löffelmann, H., Ribarsky, W.
    Volume rendering with texture mapping hardware is a fast volume rendering method available on high-end workstations. However, limited texture memory often prevents the method from being used to render large volume data efficiently. In this paper, we propose a new approach to fast rendering of large volume data with texture mapping hardware. Based on a new volume-loading pipeline, the volume data is preprocessed in such a way that only the volume data that contains object voxels are loaded into texture memory and resampled for rendering. Moreover, if classification threshold is changed, our algorithm classifies and processes the raw volume data accordingly nearly in real time. Our tests show that about 40% to 60% rendering time is saved in our method for large volume data.
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    An Informed Environment Dedicated to the Simulation of Virtual Humans in Urban Context
    (Blackwell Publishers Ltd and the Eurographics Association, 1999) Farenc, Nathalie; Boulic, Ronan; Thalmann, Daniel
    In this paper, we outline the creation of an Informed Environment, dedicated to urban life simulation.We propose methods and tools for creating and providing the information necessary for animating virtual humans in a city using an Informed Environment. The Informed Environment is based on a hierarchical decomposition of a urban scene into Environment Entities providing geometrical information as well as semantic notions, thus allowing a more realistic simulation of human behaviour. In this manner, virtual humans can integrate with a certain kind of urban knowledge.