STARs

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https://diglib.eg.org/handle/10.2312/221

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Now showing 1 - 6 of 6
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    The 3D Model Acquisition Pipeline
    (Eurographics Association, 2000) Bernardini, Fausto; Rushmeier, Holly
    Three-dimensional image acquisition systems are rapidly becoming more affordable, especially systems based on commodity electronic cameras. At the same time, personal computers with graphics hardware capable of displaying complex 3D models are also becoming inexpensive enough to be available to a large population. As a result, there is potentially an opportunity to consider new virtual reality applications as diverse as cultural heritage and retail sales that will allow people to view realistic 3D objects on home computers. Although there are many physical techniques for acquiring 3D data – including laser scanners, structured light and time-of-flight – there is a basic pipeline of operations for taking the acquired data and producing a usable numerical model. We look at the fundamental problems of range image registration, line-of-sight errors, mesh integration, surface detail and color, and texture mapping. In the area of registration we consider both the problems of finding an initial global alignment using manual and automatic means, and refining this alignment with variations of the Iterative Closest Point methods. To account for scanner light-of-sight errors we compare averaging and conformance approaches. In the area of mesh integration, that is finding a single mesh joining the data from all scans, we compare various methods for computing interpolating and approximating surfaces. We then look at various ways in which surface properties such as color (more properly, spectral reflectance) can be extracted from acquired imagery. Finally, we examine techniques for a producing a final model representation that can be efficiently rendered using graphics hardware.
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    Geometric Signal Processing on Polygonal Meshes
    (Eurographics Association, 2000) Taubin, G.
    Very large polygonal models, which are used in more and more graphics applications today, are routinely generated by a variety of methods such as surface reconstruction algorithms from 3D scanned data, isosurface construction algorithms from volumetric data, and photogrametric methods from aerial photography. In this report we provide an overview of several closely related methods developed during the last few yers, to smooth, denoise, edit, compress, transmit, and animate very large polygonal models.
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    Interactive Display of Global Illumination Solutions for Non-Diffuse Environments
    (Eurographics Association, 2000) Heidrich, Wolfgang
    In recent years there has been a lot of work on interactively displaying global illumination solutions for nondiffuse environments. This is an extremely active field of research, in which a lot of different approaches have been proposed recently. In this State-of-The-Art-Report, we will discuss and compare these. This will hopefully lay the ground for systematically addressing the open questions in the future.
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    Recent Advances in Visualization of Volumetric Data
    (Eurographics Association, 2000) Brodlie, Ken; Wood, Jason
    In the past few years, there have been key advances in the three main approaches to the visualization of volumetric data: isosurfacing, slicing and volume rendering, which together make up the field of volume visualization. In this report we set the scene by describing the fundamental techniques for each of these approaches, using this to motivate the range of advances which have evolved over the past few years. In isosurfacing, we see how the original marching cubes algorithm has matured, with improvements in robustness, topological consistency, accuracy and performance. In the performance area, we look in detail at pre-processing steps which help identify data which contributes to the particular isosurface required. In slicing too, there are performance gains from identifying active cells quickly. In volume rendering, we describe the two main approaches of ray casting and projection. Both approaches have evolved technically over the past decade, and the holy grail of real-time volume rendering has arguably been reached. The aim of this Eurographics 2000 STAR is to pull these developments together in a coherent review of recent advances in volume visualization.
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    Shadow Computation: A Unified Perspective
    (Eurographics Association, 2000) Ghali, S.; Fiume, E.; Seidel, H.-P.
    Methods for solving shadow problems by solving instances of visibility problems have long been known and exploited. There are, however, other potent uses of such a reduction of shadow problems, several of which we explore in this paper. Specifically, we describe algorithms that use a resolution–independent, or object–space, visibility structure for the computation of object–space shadows under point, linear, and area light sources. The connection between object–space visibility and shadow computation is well–known in computer graphics. We show how that fundamental observation can be recast and generalized within an object–space visibility structure. The edges in such a structure contain exactly the information needed to determine shadow edges under a point light source. Also, the locations along a linear or an area light source at which visibility changes (termed critical points and critical lines) provide the necessary information for computing shadow edges resulting from linear and area light sources. Not only are instances of all shadow problems thus reduced to visibility problems, but instances of shadow problems under linear and area light sources are also reduced to instances of shadow generation under point and linear light sources, respectively.
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    Visual Perception in Realistic Image Synthesis
    (Eurographics Association, 2000) McNamara, A.; Chalmers, A.; Trocianko, T.
    Realism is often a primary goal in computer graphics imagery, we strive to create images that are perceptually indistinguishable from an actual scene. Rendering systems can now closely approximate the physical distribution of light in an environment. However, physical accuracy does not guarantee that the displayed images will have authentic visual appearance. In recent years the emphasis in realistic image synthesis has begun to shift from the simulation of light in an environment to images that look as real as the physical environment they portray. In other words the computer image should be not only physically correct but also perceptually equivalent to the scene it represents. This implies aspects of the Human Visual System (HVS) must be considered if realism is required. Visual perception is employed in many different guises in graphics to achieve authenticity. Certain aspects of the human visual system must be considered to identify the perceptual effects that a realistic rendering system must achieve in order to effectively reproduce a similar visual response to a real scene. This state-of-the-art report outlines the manner in which knowledge about visual perception is increasingly appearing in state-of-the-art realistic image synthesis. This STAR is organised into three sections, each exploring the use of perception in realistic image synthesis, each with slightly different emphasis and application. First, perception driven rendering algorithms are described, these algorithms focus on embedding models of the Human Visual System (HVS) directly into global illumination computations in order to improve their efficiency. Then perception based image quality metrics, which aim to compare images on a perceptual rather than physical basis are presented. These metrics can be used to evaluate, validate and compare imagery. Finally, Tone Reproduction Operators, which attempt to map the vast range of computed radiance values to the limited range of display values, are discussed.