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Computer Graphics, Spring Conference on, 2001.

Date 25-28 April 2001

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Displaying Results 1 - 25 of 30
  • Proceedings Spring Conference on Computer Graphics

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    Freely Available from IEEE
  • Table of contents

    Page(s): 249
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    Freely Available from IEEE
  • Shape of toric surfaces

    Page(s): 55 - 62
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (548 KB) |  | HTML iconHTML  

    We present an informal introduction to the theory of toric surfaces from the viewpoint of geometric modeling. Bezier surfaces and many well-known low-degree rational surfaces are found to be toric. Bezier-like control point schemes for toric surfaces are defined via mixed trigonometric-polynomial parametrizations. Many examples are considered: quadrics, cubic Mobius strip, quartic 'pillow', 'crosscap' and Dupin cyclides. A 'pear' shape modeling is presented View full abstract»

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  • An octree isosurface codification based on discrete planes

    Page(s): 130 - 137
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB) |  | HTML iconHTML  

    Describes a method to code a decimated model of an isosurface on an octree representation while maintaining volume data if it is needed. The proposed technique is based on grouping the marching cubes (MC) patterns into five configurations according the topology and the number of planes of the surface that are contained in a cell. Moreover, the discrete number of planes on which the surface lays is fixed. Starting from a complete volume octree, with the isosurface codified at terminal nodes according to the new configuration, a bottom-up strategy is taken for merging cells. Such a strategy allows one to implicitly represent co-planar faces in the upper octree levels without introducing any error. At the end of this merging process, when it is required, a reconstruction strategy is applied to generate the surface contained in the octree intersected leaves. Some examples with medical data demonstrate that a reduction of up to 50% in the number of polygons can be achieved View full abstract»

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  • Quadratic interpolation in hardware Phong shading and texture mapping

    Page(s): 181 - 188
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (684 KB) |  | HTML iconHTML  

    Rendering systems often represent curved surfaces as a mesh of planar polygons that are shaded to add realism and to restore a smooth appearance. To increase the rendering speed, complex operations, such as the evaluation of the local illumination model or texture transformation, are executed for just a few knot points, and the values at other points are interpolated. Usually, a linear transformation is used, since it can be easily implemented in hardware. However, the colour distribution and texture transformation may be strongly nonlinear, so a linear interpolation may introduce severe artifacts. Thus, this paper proposes two-variate quadratic interpolation to tackle this problem and demonstrates that it can be implemented in hardware. A software simulation and a VHDL description of the shading hardware are also presented View full abstract»

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  • Vessel tracking in peripheral CTA datasets-an overview

    Page(s): 232 - 239
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (812 KB) |  | HTML iconHTML  

    We describe the results of the literature review focused on the peripheral vessel segmentation in 3D medical datasets, acquired by computer tomography angiography (CTA) of the human leg. The fundamental aim of such a segmentation task is a robust method for the detection of main vessels in the leg that simultaneously preserves the vessel calcification (the sediment is called plaque) and allows localization of vessel narrowings (called stenoses). This segmentation has to be free from artifacts, i.e., without false detections of stenoses and without false omitting of any stenotic part. The paper collects seven methods applicable for vessel segmentation View full abstract»

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  • On the domain of constructive geometric constraint solving techniques

    Page(s): 49 - 54
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB) |  | HTML iconHTML  

    We study the domain of two constructive geometric constraint solving techniques. Both deal with constraints represented by a geometric constraint graph. The first technique analyses the graph bottom-up, from the edges to the whole graph. The second technique analyses the graph top-down, from the whole graph to the individual edges. We describe these techniques using abstract reduction systems which simplifies the study of their properties. We present an abstract description of the domain of each technique. Finally, we show that both techniques have the same domain, that is, they solve the same kind of problems defined by geometric constraints View full abstract»

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  • Smooth high-quality interactive visualization

    Page(s): 87 - 94
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (684 KB) |  | HTML iconHTML  

    The paper addresses the problem of interactive visualization in the view-dependent simplification framework. A geomorphing algorithm for interpolation between different levels of detail is given. The interpolation parameter is derived from the screen-space geometric error instead of assigning a fixed transition time to the interpolation process. Furthermore, a hybrid frame rate control system is proposed. Frame time is predicted based on the average rendering time per triangle, reducing oscillation and overshooting. A set of experiments demonstrates the advantages of both methods View full abstract»

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  • Automatic instancing of hierarchically organized objects

    Page(s): 63 - 70
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (644 KB) |  | HTML iconHTML  

    Instancing is an approved concept to save space for the storage of three dimensional scenes. The authors propose an algorithm to automatically create instances from objects that are organized in a hierarchical scene graph. They present a definition of instancing and derive an algorithm from that. The authors also discuss results of tests done with their implementation of the algorithm and give options for further development View full abstract»

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  • Texturing through constructive modeling

    Page(s): 190 - 200
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1132 KB) |  | HTML iconHTML  

    The concept of solid texturing is extended in two directions: constructive modeling of space partitions for texturing and modeling of multi-dimensional textured objects called hypervolumes. A hypervolume is considered as a point set with attributes of both physical (density, temperature, etc.) and photometric (color, transparency, diffuse and specular reflections, etc.) nature. The point-set geometry and attributes are modeled independently using real-valued scalar functions of several variables. Each real-valued function defining the geometry or an attribute is evaluated in the given point by a procedure traversing a constructive tree structure with primitives in the leaves and operations in the nodes of the tree. This approach provides a framework for the modeling, texturing and visualization of 3D solids and time-dependent and multi-dimensional objects in a completely uniform manner. We introduced a special modeling language and implemented software tools supporting the proposed approach. The concept of constructive hypervolume textures is independent of the geometric representation. We provide examples of textured functional representation (F-Rep) and boundary representation (B-Rep) objects as illustrations View full abstract»

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  • Topological graphics

    Page(s): 2 - 9
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (736 KB) |  | HTML iconHTML  

    Topological graphics opens up completely new worlds in computer graphics applications. It is supported by advances in modern algebraic topology homotopy theory and cellular spatial structures in particular. Topological graphics lays out the framework to interactively construct cyberworlds emerging on the World Wide Web. It guides graphics software design to make it minimal and reusable. This progress report on our own frontier researches gives abundant examples as well as a brief summary of theoretical foundations View full abstract»

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  • Some new challenging research topics in human animation

    Page(s): 12 - 20
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (892 KB) |  | HTML iconHTML  

    The paper aims at defining new challenging research topics related to human simulation and animation. Although virtual human modelling, animation and simulation aspects have now been widely studied, there remain many topics and applications that are still open for research. Among them, we propose a survey of the current status and the future directions of research topics and applications such as virtual cloning and population and crowd modelling, clothing simulation, communication and interaction with virtual humans thanks to emotional dialogue, avatars and autonomous virtual embodiments in an inhabited virtual environment for cultural heritage View full abstract»

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  • Mixture of random walk solution and quasi-random walk solution to global illumination

    Page(s): 211 - 217
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (700 KB) |  | HTML iconHTML  

    Conventional Monte Carlo methods are often used to solve some hard second kind Fredholm integral equations such as the difficult global illumination problems due to its dimensional independence. However, the convergence rate of the quasi-Monte Carlo methods for numerical integration is superior to that of the Monte Carlo methods. We present two mixed strategies that make use of both the statistical properties of random numbers and the uniformity properties of quasi-random numbers to build up walk histories for solving the global illumination. In the framework of the proposed strategies, experimental results have been obtained from rendering the test scenes. The computations indicate that the mixed strategies can outperform Monte Carlo or quasi-Monte Carlo used alone View full abstract»

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  • Perspective projection through parallel projected slabs for virtual endoscopy

    Page(s): 241 - 248
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (856 KB) |  | HTML iconHTML  

    Virtual endoscopy is a promising medical application for volume rendering techniques where perspective projection is mandatory. Most of the acceleration techniques for direct volume rendering make use of parallel projection. This is also the case of the current generation of VolumePro systems, which achieve real-time frame rates but unfortunately just provide parallel projection. In this paper, an algorithm to approximate perspective volume rendering using parallel projected slabs is presented. The introduced error due to the approximation is investigated. Based on the error estimation, an improvement to the basic algorithm is presented. The improvement increases the frame rate keeping the global maximal error bounded. The usability of the algorithm is shown through the virtual endoscopic investigation of various types of medical data sets View full abstract»

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  • Post-optimization of Delaunay tetrahedrization

    Page(s): 31 - 38
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (584 KB) |  | HTML iconHTML  

    The paper brings results of post-optimization of Delaunay tetrahedrization. Delaunay triangulation is a very popular method to create 2D meshes, but in 3D its properties are not as good as in 2D and can be improved. For this improvement an already existing method was used: local transformations, so called flips, performed in order to improve different geometrical properties of tetrahedra and applied to the finished 3D Delaunay triangulation. We examined this method by using various criteria to compare their benefits and losses in the area of the tetrahedra shape or time demand. We found out that the greatest benefit comes from the so called compound criteria and from the criterion which minimizes the numbers of tetrahedra. Other criteria have no positive influence on mesh improvement, they rather degrade the quality of the Delaunay mesh. The question of time is not so important, because all criteria are fast enough (they take at most 10 percent of time needed to construct a Delaunay mesh) View full abstract»

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  • A colour reindexing algorithm for lossless compression of digital images

    Page(s): 104 - 108
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB) |  | HTML iconHTML  

    The efficiency of lossless compression algorithms for fixed palette images (also called indexed images) changes if a different indexing scheme is adopted. Indeed, these algorithms adopt a differential-predictive approach of some sort: if the spatial distribution of the indexes over the image is smooth, greater compression ratios may be obtained. It hence becomes relevant to find an indexing scheme that realizes such a smooth distribution. This seems to be a hard problem, and only approximate answers can be provided if a realistic run-time has to be achieved. In this paper, we propose a new indexing scheme, based on an approximate algorithm that maximizes the cost of a Hamiltonian path in a weighted graph. The proposed technique compares favourably with the algorithm proposed by W. Zeng et al. (2000). The computational complexity of the two algorithms is compared and experimental tests that show that relative compression rates are reported View full abstract»

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  • Interactive display of surfaces using subdivision surfaces and wavelets

    Page(s): 118 - 127
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (908 KB) |  | HTML iconHTML  

    Complex surfaces and solids are produced by large-scale modeling and simulation activities in a variety of disciplines. Productive interaction with these simulations requires that these surfaces or solids should be viewable at interactive rates - yet many of these surfaces/solids can contain hundreds of millions of polygons/polyhedra. Interactive display of these objects requires compression techniques to minimize storage, and fast view-dependent triangulation techniques to drive the graphics hardware. In this paper, we review recent advances in subdivision-surface wavelet compression and optimization that can be used to provide a framework for both compression and triangulation. These techniques can be used to produce suitable approximations of complex surfaces of arbitrary topology and can be used to determine suitable triangulations for display. The techniques can be used in a variety of applications in computer graphics, computer animation and visualization View full abstract»

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  • A new efficient wave model for maritime training simulator

    Page(s): 202 - 209
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (772 KB) |  | HTML iconHTML  

    The market for maritime training simulators is as important as the market for aeronautical training simulators. Many maritime accidents are caused by piloting errors in critical situations. Such situations are usually due to the environment (waves and streams). Hence, the main challenge of a maritime simulator is to simulate this environment as accurately as possible and, more precisely, to simulate ocean waves. Nowadays, two kinds of wave simulation theories are being presented. Firstly, accurate models are being created by physicists, while in computer graphics, researchers are putting forward some simpler physically-based models in order to produce static photorealistic images. This paper describes a new, efficient, real-time model of wave propagation and shows its integration in a real maritime simulator View full abstract»

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  • High precision non-binary voxelization of geometric objects

    Page(s): 220 - 229
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1004 KB) |  | HTML iconHTML  

    Volume graphics represents a set of techniques aimed at modeling, manipulation and rendering of objects represented by means of a 3D raster of elementary volume primitives-voxels. It represents a viable alternative for the standard surface graphics, and as such, it provides us with a possibility to overcome some of its bottlenecks and to extend its capabilities even further. Namely, by means of voxelization, it decouples object specific issues from rendering and enables uniform representation of all objects by a single primitive, the voxel. Thus, instead of dealing with a number of different objects with specific features, a renderer processes only one primitive object, which simplifies its architecture and leads to a more effective implementation. Moreover, rendering is independent on the original number of objects and hence a complete independence on object and scene complexity is achieved. Voxelization, i.e. a conversion of object representation by means of analytic formulas to the discrete 3D raster stands in the core of volume graphics techniques. We present and critically analyze distance oriented techniques as a tool for alias free volumetric representation of geometric objects View full abstract»

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  • View-dependent information theory quality measures for pixel sampling and scene discretization in flatland

    Page(s): 173 - 180
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    In this paper, we present view-dependent information theory quality measures for pixel sampling and scene discretization in flatland. The measures are based on a definition for the mutual information of a line, and have a purely geometrical basis. Several algorithms exploiting them are presented and compare well with an existing one based on depth differences View full abstract»

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  • Growth simulation of human embryo brain

    Page(s): 139 - 145
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (672 KB) |  | HTML iconHTML  

    The growth of the brain of a human embryo changes over a long period of time in the body of the mother. So it is very difficult to observe and to understand that process. Therefore, embryologists have found realistic human organ models and animations to be necessary for their studies, but to create realistic human embryo brain models and to perform the animations requires an appropriate methodology. This paper presents a developing methodology based on the brain's functional representation and the convolutions of the surfaces. We employed this methodology to create a growth simulation of a human embryo's brain. The idea behind this technique is as follows. As a first step a 2D central skeleton is created from an artistic drawing and then a 3D skeleton is modeled by adding thickness information. In the next step, the skeletons representing the key-frame models are used to create an animation. At the end, the gap between the key-frame models is filled by suitable interpolation techniques and, finally, the animation is composed View full abstract»

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  • An efficient technique for ray tracing of a D0L-system

    Page(s): 165 - 172
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (624 KB) |  | HTML iconHTML  

    Presents an algorithm which aims at reducing the execution time and memory requirements of the synthesis of plants which are generated by a D0L system (deterministic context-free Lindenmayer system) and rendered by ray tracing. We propose a new method that carries out an intersection test directly with the production obtained by a D0L system, and thus attain considerable size reduction in the database. To reduce the computation time, the method works with a bounding volume hierarchy and adapts to the available memory by storing the hierarchy as far as a certain depth. Both the graphical primitives and those bounding volumes that have not been stored in memory are calculated at tracing time when they are required. We have compared our intersection test with a classical intersection test and with the commercial ray tracer PovRay, obtaining important reductions in computation time and memory in both cases View full abstract»

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  • Taylor models and affine arithmetics-towards a more sophisticated use of reliable methods in computer graphics

    Page(s): 40 - 47
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (628 KB) |  | HTML iconHTML  

    A critical discussion of existing applications of reliable methods in computer graphics and the fact that one of the key applications of reliable arithmetics in computer graphics is its use for range analysis provokes a reconsideration of existing ideas of bounding volumes. A novel kind of parametrized bounding volume for parametric surfaces is proposed that informs about the location of each surface point and the corresponding parameters, as well as the location of the surface . Taylor models and the intrinsic structure of affine arithmetic are used to realize the discussed concepts in the form of linear interval estimations (LIEs). The sophisticated use of reliable methods and the characteristics of LIEs allow an effective intersection test for LIEs that also gives information about those parts of the parameter domains possibly affected by an intersection of the enclosed surface patches. A novel subdivision algorithm for the intersection of two parametric surfaces with remarkable experimental results is presented as a possible application for LIEs View full abstract»

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  • Layered data representation for visual simulation of terrain erosion

    Page(s): 80 - 86
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (820 KB) |  | HTML iconHTML  

    New data structure for visual simulation of 3D terrains is introduced. The representation is inspired by real geological measurements and presents good trade-off between commonly used inexpensive, but inaccurate, height fields and memory demanding voxel representation. The representation is based on horizontal stratified layers consisting of one material. The layers are captured in certain positions of the landscape. This representation is then discretized into a 2D array. We demonstrate that the classical algorithm simulating thermal erosion (F.K. Musgrave, 1989), can run on this representation and we can even simulate some new properties. The simulation has been done on artificial data as well as on real data from Mars View full abstract»

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  • Exploiting temporal and spatial coherence in hierarchical visibility algorithms

    Page(s): 156 - 163
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    Presents a series of simple improvements that make use of temporal and spatial coherence in the scope of hierarchical visibility algorithms. The hierarchy updating avoids visibility tests of certain interior nodes of the hierarchy. The visibility propagation algorithm reuses information about visibility of neighbouring spatial regions. Finally, the conservative hierarchy updating avoids visibility tests of the hierarchy nodes that are expected to remain visible. We evaluate the presented methods in the context of hierarchical visibility culling using occlusion trees View full abstract»

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