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A computational scheme is presented that takes into account the topography, i.e. the shadowing and hence the local emission angle of the electrons when evaluating AR-XPS data of macroscopic rough surfaces. The topography of the sample surface is supposed to be recorded by atomic force microscopy and/or opticalmicroscopy. The emitted photoelectrons are simulated based on an extension of the Beer-Lambert law that includes the shadowing, the current local emission angle, and the geometrical instrument setup. The obtained angle-resolved XPS spectra are optimized in accordance with experimental ones via a self-consistentminimization algorithmthat also allows one to determine the layer thicknesses of the corrugated sample. In order to validate the proposed numerical scheme, the simulationprogram simulationof electron spectra for surface analysis is used. An additional analysis is then performed considering only experimental data. The numerical scheme gives good agreement in simulation-simulation as well as simulation-experiment comparisons and permits a comprehensible interpretation of themeasured data. [ABSTRACT FROM AUTHOR]

Global illumination systems require intervisibility information between pairs of points in a scene. This visibility problem is computationally complex, and current interactive implementations for dynamic scenes are limited to crude approximations or small amounts of geometry. We present a novel algorithm to determine intervisibility from all points of dynamic height fields as visibility horizons in discrete azimuthal directions. The algorithm determines accurate visibility along each azimuthal direction in time linear in the number of output visibility horizons. This is achieved by using a novel visibility structure we call the convex hull tree. The key feature of our algorithm is its ability to incrementally update the convex hull tree such that at each receiver point only the visible parts of the height field are traversed. This results in low time complexity; compared to previous work, we achieve two orders of magnitude reduction in the number of algorithm iterations and a speedup of 2.4 to 41 on height fields, depending on geometric content. [ABSTRACT FROM AUTHOR]

Geodesic Polar Coordinates (GPCs) on a smooth surface S are local surface coordinates that relates a surface point to a planar parameter point by the length and direction of a corresponding geodesic curve on S. They are intrinsic to the surface and represent a natural local parameterization with useful properties. We present a simple and efficient algorithm to approximate GPCs on both triangle and general polygonal meshes. Our approach, named DGPC, is based on extending an existing algorithm for computing geodesic distance. We compare our approach with previous methods, both with respect to efficiency, accuracy and visual qualities when used for local mesh texturing. As a further application we show how the resulting coordinates can be used for vector space methods like local remeshing at interactive frame-rates even for large meshes. [ABSTRACT FROM AUTHOR]

In this paper, we propose an instant shadow generation technique for 2D animation, especially Japanese Anime. In traditional 2D Anime production, the entire animation including shadows is drawn by hand so that it takes long time to complete. Shadows play an important role in the creation of symbolic visual effects. However shadows are not always drawn due to time constraints and lack of animators especially when the production schedule is tight. To solve this problem, we develop an easy shadowing approach that enables animators to easily create a layer of shadow and its animation based on the character's shapes. Our approach is both instant and intuitive. The only inputs required are character or object shapes in input animation sequence with alpha value generally used in the Anime production pipeline. First, shadows are automatically rendered on a virtual plane by using a Shadow Map1 based on these inputs. Then the rendered shadows can be edited by simple operations and simplified by the Gaussian Filter. Several special effects such as blurring can be applied to the rendered shadow at the same time. Compared to existing approaches, ours is more efficient and effective to handle automatic shadowing in real-time. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

If there is a frequency offset in the local oscillator circuit in QPSK demodulation, the BER is degraded. Previously, methods for estimating this frequency offset have been proposed. However, few techniques that have been studied can estimate this offset in an environment with a large frequency offset or noise. A digital adaptive IIR notch filter is effective for estimation of a large frequency offset in an environment with noise. However, the noise is colored in the receiver due to the IF band BPF inserted in order to suppress out-of-band noise. Therefore, the converged value has a bias error with respect to the target value. The method proposed in this paper is based on the fact that the phase of the digital IIR-BPF is zero at the center frequency of the amplitude characteristic. This characteristic is used for control by applying a negative feedback to the digital IIR-BPF coefficients. Then, no bias error is generated because the noise in the in-phase channel and that of the quadrature channel in QPSK are uncorrelated. Further, the proposed method does not drift but maintains the present status due to the uncorrelated character described above, even in the case of channel disconnection such as shadowing. Therefore, this is a frequency offset estimation method suitable for mobile communications. As a result of evaluation of the proposed method in terms of the BER in a white Gaussian noise channel, it is confirmed that the proposed method provides a BER lower than that of the conventional digital adaptive IIR notch filter. © 2003 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 86(9): 1–12, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.10089 [ABSTRACT FROM AUTHOR]