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Now showing 1 - 10 of 39
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    An Effective Hardware Architecture for Bump Mapping Using Angular Operation
    (The Eurographics Association, 2003) Lee, S. G.; Park, W. C.; Lee, W. J.; Han, T. D.; Yang, S. B.; M. Doggett and W. Heidrich and W. Mark and A. Schilling
    In this paper, we propose an effective bump mapping algorithm that utilizes the reference space with the polar coordinate system and also propose a new hardware architecture associated with the proposed bump mapping algorithm. The proposed architecture reduces the computations to transform the vectors from the object space into the reference space by using a new vector rotation method. It also reduces the computations for the illumination calculation by using the law of cosine. Compared with the previous approaches, the proposed architecture reduces multiplication operations up to 78%.
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    Real-Time Bump Map Synthesis
    (The Eurographics Association, 2001) Kautz, Jan; Heidrich, Wolfgang; Seidel, Hans-Peter; Kurt Akeley and Ulrich Neumann
    In this paper we present a method that automatically synthesizes bump maps at arbitrary levels of detail in real-time. The only input data we require is a normal density function; the bump map is generated according to that function. It is also used to shade the generated bump map. The technique allows to infinitely zoom into the surface, because more (consistent) detail can be created on the fly. The shading of such a surface is consistent when displayed at different distances to the viewer (assuming that the surface structure is self-similar). The bump map generation and the shading algorithm can also be used separately.
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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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    SPAF: Sub-texel Precision Anisotropic Filtering
    (The Eurographics Association, 2001) Shin, Hyun-Chul; Lee, Jin-Aeon; Kim, Lee-Sup; Kurt Akeley and Ulrich Neumann
    Texture mapping is a technique which most effectively improves the realism of computer-generated scenes in 3D Graphics. Trilinear filtering of the mip-mapped textue has been popular as a texture filtering method but it blurs images on the surface of objects angled obliquely away from the viewer in a scene. Various anisotropic filtering methods like footprint assembly, Feline, and fast footprint mip-mapping have been proposed to satisfy the desire for the high quality image [7]. In spite of the increase of the memory bandwidth, tie memory bandwidth limit is still the bottleneck of the texture filtering hardware. Moreover, it is very important to keep the quality of rendered image good. In this paper, we propose Sub-texel Precision Anisonopic Filtering (SPAF) which filters texels in a region that covers a quadrilateral footprint with the weights. The weight plays a key role in effective filtering to render the image of high quality with the restricted number of texels loaded from memory for real-time filtering. First, the area coverage based texel filtering scheme is introduced to obtain the footprint's coverage for each texel on the sub-texel precision leading to the small weight table size. Second, the Gaussian weight is applied to this footprinfs coverage for each texel to reduce the artifacts. Therefore, the quality of rendered images is superior to other anisotropic filtering methods in the same restricted number of texels. And the size ofthis weight table is several hundred KBytes which is much smaller than fast footprint mip-mapping. This small ROM table size enables the SPAF to be implemented at feasible hardware costs.
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    Parallel Texture Caching
    (The Eurographics Association, 1999) lgehy, Homan; Eldridge, Matthew; Hanrahan, Pat; A. Kaufmann and W. Strasser and S. Molnar and B.- O. Schneider
    The creation of high-quality images requires new functionality and higher performance in real-time graphics architectures. In terms of functionality, texture mapping has become an integral component of graphics systems, and in terms of performance, parallel techniques are used at all stages of the graphics pipeline. In rasterization, texture caching has become prevalent for reducing texture bandwidth requirements. However, parallel rasterization architectures divide work across multiple functional units, thus potentially decreasing the locality of texture references. For such architectures to scale well, it is necessary to develop efficient parallel texture caching subsystems. We quantify the effects of parallel rasterization on texture locality for a number of rasterization architectures, representing both current commercial products and proposed future architectures. A cycle-accurate simulation of the rasterization system demonstrates the parallel speedup obtained by these systems and quantities inefficiencies due to redundant work, inherent parallel load imbalance, insufftcient memory bandwidth, and resource contention. We find that parallel texture caching works well, and is general enough to work with a wide variety of rasterization architectures.
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    VoxelCache: A Cache-Based Memory Architecture for Volume Graphics
    (The Eurographics Association, 2003) Kanus, U.; Wetekam, G.; Hirche, J.; M. Doggett and W. Heidrich and W. Mark and A. Schilling
    This paper presents a cache-based memory architecture for volume graphics. We describe the memory organization and cache logic to implement a voxel cache based on 43 voxel blocks. We show an efficient prefetching scheme that increases the cache hit ratio to more than 98% in most cases. The performance of the memory system with different types of external memory is demonstrated by a cycle accurate C++ simulation. The VoxelCache memory architecture is designed to be easily adapted to different memory technologies, because all volume graphics specific parts of the memory system are encapsulated inside the on-chip cache. The design is targeted at implementation on off-the-shelf reconfigurable hardware.
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    Memory Access Patterns of Occlusion-Compatible 3D Image Warping
    (The Eurographics Association, 1997) Murk, William R.; Bishop, Gary; A. Kaufmann and W. Strasser and S. Molnar and B.-O. Schneider
    McMillan and Bishop s 3D image warp can be efficiently implemented by exploiting the coherency of its memory accesses. We analyze this coherency, and present algorithms that take advantage of it. These algorithms traverse the reference image in an occlusion-compatible order, which is an order that can resolve visibility using a painter s algorithm. Required cache sizes are calculated for several one-pass 3D warp algorithms, and we develop a two-pass algorithm which requires a smaller cache size than any of the practical one-pass algorithms. We also show that reference image traversal orders that are occlusion-compatible for continuous images are not always occlusion-compatible when applied to the discrete images used in practice.
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    Texture Mapping Volume Objects
    (The Eurographics Association, 2005) Shen, P.; Willis, P.; Mike Chantler
    We present a combination of image-based texture mapping and projective space (pseudo-solid) texture. This imagebased texture mapping is useful for objects defined from volume datasets. The paper makes three main contributions. First, it introduces the combination of the image-based two-part texture mapping and projective space texture mapping for volume objects. Second, it presents a multi-resolution technique to overcome problems with projecting at glancing angles and to eliminate artifacts due to the resolution limitations. Third, it presents the pixel-level data-dependent interpolation technique in projective image warping. The proposed approach leads to superior quality of texture and thus provides an optional solution for texturing volume objects.The results show the effectiveness and quality of rendered images.
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    An Optimized Soft Shadow Volume Algorithm with Real-Time Performance
    (The Eurographics Association, 2003) Assarsson, Ulf; Dougherty, Michael; Mounier, Michael; Akenine-Möller, Tomas; M. Doggett and W. Heidrich and W. Mark and A. Schilling
    In this paper, we present several optimizations to our previously presented soft shadow volume algorithm. Our optimizations include tighter wedges, heavily optimized pixel shader code for both rectangular and spherical light sources, a frame buffer blending technique to overcome the limitation of 8-bit frame buffers, and a simple culling algorithm. These together give real-time performance, and for simple models we get frame rates of over 150 fps. For more complex models 50 fps is normal. In addition to optimizations, two simple techniques for improving the visual quality are also presented.
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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.