Haptic, or force, interaction in virtual environments can support the development of physical manipulation skills if users feel realistic forces in response to their motion in the virtual environment. The realism of the forces felt by users depends on: (i) how accurately the virtual environment simulates a real life situation such as surgery; and (ii) how faithfully the haptic controller renders the simulated interactions to users. Accurate simulations of real life situations such as surgery run at variable frequencies of the order of 20-100 Hz. However, the haptic controller needs updated stiffness and direction of contact at 1000 Hz to faithfully convey the shape and hardness of the virtual objects to the user. This thesis proposes to bridge the gap between the required fast haptic control rate and the slower virtual environment updates through a passive local model of interaction. This model comprises an approximation of the shape and stiffness of the virtual world in the area near the point of interaction. It also monitors its exchange of energy with the user to ensure its own passivity and thus, the stability of the haptic system. Lastly, the local model eliminates the spurious discontinuities that arise in contact direction at model updates by interpolating the contact normal before rendering it to the user. / Graduate

Orientador: Martin Tygel / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociências / Made available in DSpace on 2018-08-27T15:05:45Z (GMT). No. of bitstreams: 1 Vasconcelos_TabajaraWilliamsVilela_M.pdf: 7596247 bytes, checksum: 87f367837309475d85211f828eb1929f (MD5) Previous issue date: 2015 / Resumo: Dados sísmicos dispostos em grades densas e regulares são essenciais em vários objetivos de processamento, imageamento e inversão. Exemplos de tais objetivos incluem a eliminação de múltiplas de superfície (SRME) e migração baseada na equação da onda (WEM). Dados de sísmica de reflexão são geralmente sub-amostrados e as razões para isso incluem limitações físicas (por exemplo, comprimento finito dos cabos, dificuldades topográficas e ambientais), falhas instrumentais (por exemplo, traços ruins ou inexistentes) e, acima de tudo, a amostragem espacial densa é cara. Para superar o problema de subamostragem, bem como os deslocamentos dos dados da malha regular, é necessário reconstruir os dados faltantes a partir dos dados adquiridos. Em outras palavras, é preciso realizar interpolação e/ou extrapolação dos dados existentes. Este trabalho discute e compara métodos de interpolação e extrapolação com base na abordagem da superfície de reflexão comum (CRS), que se baseia num certo número de atributos cinemáticas das ondas de propagação, obtidos a partir dos dados de multicobertura. A análise é realizada em três metodologias CRS, a saber: (a) empilhamento parcial (PS) CRS; (b) regularização orientada à amostra alvo (TO) CRS e (c) regularização orientada ao operador (OO) CRS. Uma breve descrição das três metodologias é realizada e, por meio de exemplos ilustrativos, examinamos suas vantagens e desvantagens / Abstract: Dense and regularly sampled seismic data are essential to a number of processing, imaging and inversion purposes. Processes such as Surface-Related Multiple Elimination (SRME) and wave-equation migration (WEM) are good examples that required data displayed on a regular grid. Seismic reflection data are usually under or irregularly sampled. Reasons for that include physical limitations (e.g., finite-length spread, topographic or environmental difficulties), instrumental failures (e.g., bad or dead traces). Above all, dense spatial sampling is expensive. To overcome the under sampling problem, as well of having the data displaced on regular grids, it is necessary to simulate the missing data from the acquired data. In other words, one needs to interpolate and/or extrapolate the given data to a user defined regular grid. This work discusses and compares interpolation and/or extrapolation methods based on the common-reflection-surface (CRS) approach, which is based on a number of kinematic wavefield attributes, extracted from the multicoverage data. The analysis will be carried out on three CRS methodologies, namely (a) the partial-stack (PS) CRS; (b) the target-oriented (TO) CRS and (c) the operator-oriented (OO) CRS. We provide a brief description of the three methodologies and, by means of illustrative examples, examine their advantages and disadvantages / Mestrado / Reservatórios e Gestão / Mestre em Ciências e Engenharia de Petróleo

The realistic animation of virtual characters can enhance user experience. Motion-editing methods such as keyframing and motion capture are effective for pre-determined animations but are incapable of real-time generation. Algorithm-based dynamic simulation and machine learning-based motion synthesis are procedural but too complex. This thesis explores an approach known as animation interpolation, which benefits from the strengths of both types of methods. Animation interpolation generates full animation sequences by assembling pre-defined motion primitives or key poses in real-time. <div><br></div><div>The purpose of this thesis is to evaluate the naturalness of character animation in three common interpolation methods: linear Euler interpolation, spherical linear quaternion interpolation, and spherical spline quaternion interpolation. Many researchers have studied the mathematical equations, motion curves, and velocity graphs of these algorithms. This thesis focuses on the perceptual evaluation and the implementation of expressive upper body character animation. </div><div><br></div><div>During the experimental studies, 97 participants watched 12 animation clips of a character performing four different upper body motions using three interpolation methods. The motions were based on McNeill’s classification of body gestures (beat gesture, deictic gesture, iconic gesture, and metaphoric gesture). After viewing each clip, the participants rated the naturalness on a 5-point Likert scale. The results showed that animations generated using spherical spline quaternion interpolation were perceived as significantly more natural than those generated from the other two interpolation methods.</div>

Image interpolation in the medical area is of vital importance as most 3D biomedical volume images are sampled where the distance between consecutive slices is significantly greater than the in-plane pixel size due to radiation dose or scanning time. Image interpolation creates a certain number of new slices between known slices in order to obtain an isotropic volume image. The results can be used for the higher quality of 2D and 3D visualization or reconstruction of human body structure. Semantic interpolation on the manifold has been proved to be very useful for smoothing the interpolation process. Nevertheless, all previous methods focused on low-resolution image interpolation, and most of which work poorly on high-resolution images. Besides, the medical field puts a high threshold for the quality of interpolations, as they need to be semantic and realistic enough, and resemble real data with only small errors permitted. Typically, people downsample the images into 322 and 642 for semantic interpolation, which does not meet the requirement for high-resolution in the medical field. Thus, we explore a novel way to generate semantically correct interpolations and maintain the resolution at the same time. Our method has been proved to generate realistic and high-resolution interpolations on the sizes of 5262 and 5122. Our main contribution is, first, we propose a novel network, High Resolution Interpolation Network (HRINet), aiming at producing semantically correct high-resolution CT image interpolations. Second, by combining the idea of ACAI and GANs, we propose a unique alternative supervision method by applying supervised and unsupervised training alternatively to raise the accuracy and fidelity of body structure in CT when interpolated while keeping high quality. Third, we introduce an extra Markovian discriminator as a texture or fine details regularizer to make our model generate results indistinguishable from real data. In addition, we explore other possibilities or tricks to further improve the performance of our model, including low-level feature maps mixing, and removing batch normalization layers within the autoencoder. Moreover, we compare the impacts of MSE based and perceptual based loss optimizing methods for high quality interpolation, and show the trade-off between the structural correctness and sharpness. The interpolation experiments show significant improvement on both sizes of 256 2 and 5122 images quantitatively and qualitatively. We find that interpolations produced by HRINet are sharper and more realistic compared with other existing methods such as AE and ACAI in terms of various metrics. As an application of high-resolution interpolation, we have done 2D volume projection and 3D volume reconstruction from axial view CT data and their interpolations. We show the great enhancement of applying HRINet for both in sharpness and fidelity. Specifically, for 2D volume projection, we explore orthogonal projection and weighted projection respectively so as to show the improved effectiveness for visualizing internal and external human body structure.

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Spatial interpolation methods were analyzed to determine the best fit for subsidence rates and to create a predictive surface for the lower Mississippi River Industrial corridor (LMRIC). Empirical Bayesian kriging, ordinary kriging, universal kriging, and Inverse Distance Weighted interpolation methods were applied to the 2004 National Oceanic and Atmospheric Administration (NOAA) published Technical Report #50 dataset and cross validation methods were utilized to determine the accuracy of each method. The mean error and root mean square error were calculated for each interpolation method, then used to detect bias and compare the predicted value with the actual observation value. Cross-validation estimates are comparable for each method statistically and visually; however, the results indicate the empirical Bayesian kriging interpolation method is the most accurate of the methods using the lowest root mean square scores. Digital elevation models for the years 2025, 2050, and 2075 were developed based on the predictive surface of subsidence rates using the results from the empirical Bayesian kriging interpolation method. Results indicate that by 2025, 30.9% of landmass in the LMRIC will be below sea level, with 41.9% below sea level by 2050, and 53.5% by 2075. Subsidence rates in the LMRIC range from approximately 28 mm to 2 mm per year. Eighteen of the 153 industrial complexes located in the LMRIC are estimated to be below sea level by the year 2075.

<p>In this thesis we systematically reexamine the classical problem of image interpolation with an aim to better preserve the structural information, such as edges and textures, in the interpolated image. We take on the technical challenge of faithfully reconstructing high frequency components because this is critical to the perceptual quality. To achieve the above goal we develop three new adaptive image interpolation methods: 1) a classification-based method that is driven by contextual information of the low resolution image and the prior knowledge extracted from a training set of high resolution images; 2) An adaptive soft-decision block estimation method that learns and adapts to varying scene structures, guided by a two-dimension piecewise autoregressive model; 3) A model-based non-linear image restoration scheme in which the model parameters and high resolution pixels are jointly estimated through non-linear least squares estimation.</p> <p>The latter part of this thesis is devoted to the research of interpolation-based image compression, which is a relatively new topic. Our research is motivated by two important applications of visual communication: low bit-rate image coding and multiple description coding. We succeed in developing standard-compliant interpolation-based compression techniques for the above two applications. In their respective categories, these techniques exceed the best rate-distortion performance reported so far in the literature.</p> / Thesis / Doctor of Philosophy (PhD)

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