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End date: 2009 × Subject: I.3.3 [Computer Graphics] × Has files: true × Start date: 2000 ×

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Now showing 1 - 10 of 27
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    Real-Time Capture, Reconstruction and Insertion into Virtual World of Human Actors
    (The Eurographics Association, 2003) Hasenfratz, J.M.; Lapierre, M.; Gascuel, J.-D.; Boyer, E.; Peter Hall and Philip Willis
    In this paper, we show how to capture an actor with no intrusive trackers and without any special environment like blue set, how to estimate its 3D-geometry and how to insert this geometry into a virtual world in real-time. We use several cameras in conjunction with background subtraction to produce silhouettes of the actor as observed from the different camera viewpoints. These silhouettes allow the 3D-geometry of the actor to be estimated by a voxel based method. This geometry is rendered with a marching cube algorithm and inserted into a virtual world. Shadows of the actor corresponding to virtual lights are then added and interactions with objects of the virtual world are proposed. The main originality of this paper is to propose a complete pipeline that can computes up to 30 frames per second. Since the rapidity of the process depends mainly on its slowest step, we present here all these steps. For each of them, we present and discuss the solution that is used. Some of them are new solutions, as the 3D shape estimation which is achieved using graphics hardware. Results are presented and discussed.
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    Squeeze: Numerical-Precision-Optimized Volume Rendering
    (The Eurographics Association, 2004) Bitter, Ingmar; Neophytou, Neophytos; Mueller, Klaus; Kaufman, Arie E.; Tomas Akenine-Moeller and Michael McCool
    This paper discusses how to squeeze volume rendering into as few bits per operation as possible while still retaining excellent image quality. For each of the typical volume rendering pipeline stages in texture map volume rendering, ray casting and splatting we provide a quantitative analysis of the theoretical and practical limits for the required bit precision for computation and storage. Applying this analysis to any volume rendering implementation can balance the internal precisions based on the desired final output precision and can result in significant speedups and reduced memory footprint.
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    Prefiltered Antialiased Lines Using Half-Plane Distance Functions
    (The Eurographics Association, 2000) McNamara, Robert; McCormack, Joel; Jouppi, Norman P.; I. Buck and G. Humphreys and P. Hanrahan
    We describe a method to compute high-quality antialiased lines by adding a modest amount of hardware to a fragment generator based upon half-plane edge functions. (A fragment contains the information needed to paint one pixel of a line or a polygon.) We surround an antialiased line with four edge functions to create a long, thin, rectangle. We scale the edge functions so that they compute signed distances from the four edges. At each fragment within the antialiased line, the four distances to the fragment are combined and the result indexes an intensity table. The table is computed by convolving a filter kernel with a prototypical line at various distances from the line s edge. Because the convolutions aren t performed in hardware, we can use wider, more complex filters with better high-frequency rejection than the narrow box filter common to supersampling antialiasing hardware. The result is smoother antialiased lines. Our algorithm is parameterized by the line width and filter radius. These parameters do not affect the rendering algorithm, but only the setup of the edge functions. Our algorithm antialiases line endpoints without special handling. We exploit this to paint small blurry squares as approximations to small antialiased round points. We do not need a different fragment generator for antialiased lines, and so can take advantage of all optimizations introduced in the existing fragment generator.
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    Regularised Anisotropic Nonlinear Diffusion for Rendering Refraction in Volume Graphics
    (The Eurographics Association, 2005) Rodgman, David; Chen, Min; Mike Chantler
    Rendering refraction in volume graphics requires smoothly distributed normals to synthesise good quality visual representations. Such refractive visualisation is more susceptible to noise in the data than visualisations that do not involve refraction. In this paper, we addresses the need for improving the continuity of voxel gradients in discretely sampled volume datasets using nonlinear diffusion methods, which was originally developed for image denoising. We consider the necessity for minimising unnecessary geometrical distortion, detail the functional specification of a volumetric filter for regularised anisotropic nonlinear diffusion (R-ANLD), discuss the further improvements of the filter, and compare the efficacy of the filter with an anisotropic nonlinear diffusion (ANLD) filter as well as a Gaussian filter and a linear diffusion filter. Our results indicate that it is possible to make significant improvements in image quality in refractive rendering without excessive distortion.
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    GPU Algorithms for Radiosity and Subsurface Scattering
    (The Eurographics Association, 2003) Carr, Nathan A.; Hall, Jesse D.; Hart, John C.; M. Doggett and W. Heidrich and W. Mark and A. Schilling
    We capitalize on recent advances in modern programmable graphics hardware, originally designed to support advanced local illumination models for shading, to instead perform two different kinds of global illumination models for light transport. We first use the new floating-point texture map formats to find matrix radiosity solutions for light transport in a diffuse environment, and use this example to investigate the differences between GPU and CPU performance on matrix operations. We then examine multiple-scattering subsurface light transport, which can be modeled to resemble a single radiosity gathering step. We use a multiresolution meshed atlas to organize a hierarchy of precomputed subsurface links, and devise a three-pass GPU algorithm to render in real time the subsurface-scattered illumination of an object, with dynamic lighting and viewing.
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    Implicit Curve and Surface Design Using Smooth Unit Step Functions
    (The Eurographics Association, 2004) Li, Q.; Gershon Elber and Nicholas Patrikalakis and Pere Brunet
    This paper presents an implicit curve and surface design technique that uses smooth unit step functions. With the proposed method, an implicit curve or surface can be generated by inputting a sequence of points together with the normals at these points of the curve or surface to be designed. By choosing appropriate smooth unit step functions, these curves and surfaces can be designed to any required degree of smoothness.
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    Interactive Rendering of Atmospheric Scattering Effects Using Graphics Hardware
    (The Eurographics Association, 2002) Dobashi, Yoshinori; Yamamoto, Tsuyoshi; Nishita, Tomoyuki; Thomas Ertl and Wolfgang Heidrich and Michael Doggett
    To create realistic images using computer graphics, an important element to consider is atmospheric scattering, that is, the phenomenon by which light is scattered by small particles in the air. This effect is the cause of the light beams produced by spotlights, shafts of light, foggy scenes, the bluish appearance of the earth s atmosphere, and so on. This paper proposes a fast method for rendering the atmospheric scattering effects based on actual physical phenomena. In the proposed method, look-up tables are prepared to store the intensities of the scattered light, and these are then used as textures. Realistic images are then created at interactive rates by making use of graphics hardware.
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    The FFT on a GPU
    (The Eurographics Association, 2003) Moreland, Kenneth; Angel, Edward; M. Doggett and W. Heidrich and W. Mark and A. Schilling
    The Fourier transform is a well known and widely used tool in many scientific and engineering fields. The Fourier transform is essential for many image processing techniques, including filtering, manip- ulation, correction, and compression. As such, the computer graphics community could benefit greatly from such a tool if it were part of the graphics pipeline. As of late, computer graphics hardware has become amazingly cheap, powerful, and flexible. This paper describes how to utilize the current gener- ation of cards to perform the fast Fourier transform (FFT) directly on the cards. We demonstrate a system that can synthesize an image by conventional means, perform the FFT, filter the image, and finally apply the inverse FFT in well under 1 second for a 512 by 512 image. This work paves the way for performing complicated, real-time image processing as part of the rendering pipeline.
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    PixelView: A View-Independent Graphics Rendering Architecture
    (The Eurographics Association, 2004) Stewart, J.; Bennett, E.P.; McMillan, L.; Tomas Akenine-Moeller and Michael McCool
    We present a new computer graphics rendering architecture that allows all possible views to be extracted from a single traversal of a scene description. It supports a wide range of rendering primitives, including polygonal meshes, higher-order surface primitives (e.g. spheres, cylinders, and parametric patches), point-based models, and image-based representations. To demonstrate our concept, we have implemented a hardware prototype that includes a 4D, z-buffered frame-buffer supporting dynamic view selection at the time of raster scan-out. As a result, our implementation supports extremely low display-update latency. The PixelView architecture also supports rendering of the same scene for multiple eyes, which provides immediate benefits for stereo viewing methods like those used in today s virtual environments, particularly when there are multiple participants. In the future, view-independent graphics rendering hardware will also be essential to support the multitude of viewpoints required for real-time autostereoscopic and holographic display devices.
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    Adaptive Texture Maps
    (The Eurographics Association, 2002) Kraus, Martin; Ertl, Thomas; Thomas Ertl and Wolfgang Heidrich and Michael Doggett
    We introduce several new variants of hardware-based adaptive texture maps and present applications in two, three, and four dimensions. In particular, we discuss representations of images and volumes with locally adaptive resolution, lossless compression of light fields, and vector quantization of volume data. All corresponding texture decoders were successfully integrated into the programmable texturing pipeline of commercial off-the-shelf graphics hardware.