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Now showing 1 - 10 of 65
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    Special Effects with Half-Toning
    (Blackwell Science Ltd and the Eurographics Association, 1996) Buchanan, John W.
    Half-toning is the process by which gray-scale images are approximated with sets of black and white pixels. The process works because our eyes perceive a local average, thus half-toning seeks to approximate the local average. Ideally this approximation should be accomplished without introducing undesirable artifacts.In many situations the stylized display of images is desired. Often this stylized display is accomplished by the addition of semi-structured artifacts. In current applications the designer processes the image using tools provided by some image processing package. The resulting image is then half-toned and printed. Half-toning these processed images can reduce the visual impact of the special effects that have been introduced in the image.In this paper we show that the processes of controlled artifact introduction and half-toning can successfully be combined. By combining these two processes we ensure that the printed image is what the designer intended. We present a brief overview of the current error-diffusion half-toning techniques. We then propose several ways in which artifacts can be introduced to the image. This discussion is accompanied by a set of illustrative images.In particular, we discuss the introduction of false edges and the alteration of the scan pattern. We illustrate these techniques with a variety of images.We conclude the paper with a discussion on these new half-toning methods for the generation of binary gray-scale textures. In addition to showing how to generate these binary gray-scale textures we also show how these gray-scale textures can be used to half-tone images.
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    Extraction of Typographic Elements from Outline Representations of Fonts
    (Blackwell Science Ltd and the Eurographics Association, 1996) Shainir, Ariel; Rappoport, Ari
    Digital typefaces for computer graphics and multimedia applications should be capable of supporting operations such as font variations, transformations. deformations and blending. A powerful implementation of such operations must rely on the inherent typographic attributes of the typeface. However, even today s most advanced typeface representations support only geometric outline representations and basic font variations.In this paper we discuss high-level typeface representations which we term Parametric Typographic Representations (PTRs). We present an algorithm for automatically extracting typographic elements of typefaces from their outline representation, which, is an essential initial step in converting typefaces from outline representations to PTRs. The extracted typographic elements include serifs, bars. sterns, slants, bows, arcs, curve stems and curve bars. Most notable is the treatment of serifs, which are represented by finite-automata. The algorithm only needs to learn a serif type once, and is then capable of automatically recognizing it in different typefaces.We show an application of a PTR for automatic high-quality hinting of fonts, which is one of the most important stages in, digital font production. Our system was used to generate hints for dozens of thousands of Kanji, Roman and Hebrew characters.
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    Animation of Human Diving
    (Blackwell Science Ltd and the Eurographics Association, 1996) Wooten, Wayne L.; Hodgins, Jessica K.
    The motion of a human platform diver was simulated using a dynamic model and a control system. The dynamic model has 32 actuated degrees of freedom and dynamic parameters within the range of those reported in the literature for humans. The control system uses algorithms for balance, jumping, and twisting to initiate the dive, sequences of desired values for proportional-derivative servos to perform the aerial portion of the dice, and a state machine to sequence the actions throughout the dice. The motion of the simulated diver closely resembles video footage of dices performed by human athletes. The control and simulation techniques presented in this paper are useful for providing realistic motion for synthetic actors in computer animations and virtual environments and may some day be useful for analysis of sports performance.
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    A Platform for User-Tailored Interaction Development in 2D, 3D, and VR
    (Blackwell Science Ltd and the Eurographics Association, 1996) Encarnacao, L. Miguel; Fechter, Jurgen; Grunert, Thomas; Strasser, Wolfgang
    The discussion on the advantages and disadvantages of 2D, 3D, and VR interfaces and their applicability to different types of systems, users, and information led to a series of stand-alone implementations that lack the possibility of realizing an integrated approach. The acceptance of the different interaction techniques will depend on their success in practical applications, i.e. with systems that are used by different users for different purposes. Since this acceptance is especially hard to achieve in computer-critical environments, such as medicine, we developed a software environment that allows for the development, integration, and user-centered evaluation of existing and new interaction techniques for their use in medical applications. This environment is equipped with an innovative message-passing functionality that provides the communication to and among application objects in 2D, 3D, and VR. Furthermore, the environment contains a component for user-adapted interaction and system support at runtime.
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    A Three Dimensional Image Cache for Virtual Reality
    (Blackwell Science Ltd and the Eurographics Association, 1996) Schaufler, Gernot; Sturzlinger, Wolfgang
    Despite recent advances in rendering hardware, large and complex virtual environments cannot be displayed with a sufficiently highframe rate, because of limitations in the available rendering performance.This paper presents a new approach of software accelerated rendering which draws from the concepts of impostors, hierarchical scene subdivision and levels of detail. So far software optimization in real-time rendering has merely considered individual objects. This work is actually optimizing the rendering of the whole virtual environment by implementing a three dimensional image cache. It speeds up rendering for large portions of the scene by exploiting the coherence inherent in any smooth frame sequence.The implementation of the three dimensional image cache is discussed and the savings in rendering load achievable on a suitable hardware platform are presented.
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    Energy Duality Methods for Piecewise Bezier Curve Construction
    (Blackwell Science Ltd and the Eurographics Association, 1996) Bercovier, M.; Volpin, O.
    Piecewise Bezier Curves are constructed using a minimization principle. Ck and GCk continuity is imposed by linear constraints. The corresponding quadratic programming with linear constraints problem is introduced and solved by duality methods. Bordering matrices methods are implemented to deal with local refinement (subdivision). The result is a versatile tool for defining/editing contours made of piecewise Bezier curves.
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    Vector Field Based Texture Mapping of Animated Implicit Objects
    (Blackwell Science Ltd and the Eurographics Association, 1996) Smets-Solanes, Jean-Paul
    This paper shows that an adequate use of vectorfields can solve most inconsistencies related to texture mapping that appear in current animation and rendering systems based on implicit objects. The method used is based on the concept of a virtual skin. A skin with its own texture mapping is spread over an implicit object and is constrained to stick to the deformation of the implicit object. A vectorfield is used to compute the relationship between the motion of the skin and the deformation of the object. Visual and implementation issues are discussed with respect to typical applications of implicit objects in computer graphics.
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    Simplification of Global-Illumination Meshes
    (Blackwell Science Ltd and the Eurographics Association, 1996) Hughes, Merlin; Lastra, Anselmo A.; Saxe, Edward
    We present a methodfor simplifying the meshes produced as solutions to global illumination problems, reducing geometric complexity while retaining the perceived imagefidelity. The method has been applied to produce meshes of linearly, quadratically and cubically colour-interpolated triangles. The goal of our work is to permit interactive rendering of more complex global illumination solutions through the application of simplification algorithms as well as the use of more powerful rendering primitives.
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    Three-Dimensional Modeling and Effects on Still Images
    (Blackwell Science Ltd and the Eurographics Association, 1996) Zakait, Yaron; Rappoport, Ari
    Designers and creative artists use computer graphics and image processing effects on stall photographs in application areas such as advertising entertainment broadcasting and the arts Most of the effects available in research arid commercial work are two-dimensional in nature, for example image processing filters [blur, edge enhancement) and creative effects (tilings, reflections) There is almost no usage of information taken from the 3-D world in which the objects appearing an the image are located.In this paper we present a novel method for creating 3-D effects on photographs or in general on any image created by rendering a 3-D world The artist interacts with the image using a set of intuitive direct manipulation interface objects These objects let the user define a 3-D model, display at, and manipulate it in a 3-D space which is correlated with that of the input image.The generated model can be an arbitrarily complex 3-D polyhedron Any texture, including texture taken from the input photograph, can be mapped into any of its faces arid used for special effects We discuss and show examples for effects such as copy and paste, motion blur, model editing and deformations lighting effects, and shadows.
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    Incremental Line Labelling for Sketch Input of Solid Models
    (Blackwell Science Ltd and the Eurographics Association, 1996) Grimstead, I. J.; Martin, R. R.
    Designers need to transfer three-dimensional objects from their minds via a two-dimensional interface into a solid modelling system. We propose a system where objects are sketched interactively in two-dimensions and incrementally line-labelled as the drawing progresses, as the preliminary stage in constructing a solid model. Once the sketch is complete, the line-labels are coupled with various inferred constraints to enable us to generate a solid model. In this paper we describe and evaluate a modification to existing line labelling methods to allow them to work incrementally. In this way, the labelling and region information can be built up as the user sketches, rather than all at once at the end of the sketching process, which reduces the delay before the final solid model is built.