Geometric shapes can be represented in a variety of different ways. A distancemap is a map from points to distances. This can be used as a shape representationwhich can be created through a process known as a distance transform. This the-sis project tests a method for three-dimensional distance transforms using frac-tional volume coverage. This method produces distance maps with subvoxel dis-tance values. The result which is achieved is clearly better than what would beexpected from a binary distance transform and similar to the one known fromprevious work. The resulting code has been published under a free and opensource software license. / <p>The developed code is available under a GPL license here https://gitlab.com/Emiluren/3d-distance-transform</p>

<p>This study describes a fast approach using GPU to process self-collision in cloth animation without significant compromise in physical accuracy. The proposed fast approach is built and works effectively on a modification of Mass Spring Model which is seen in a variety of cloth simulation study. Instead of using hierarchical data structure which needs to be updated each frame, this fast approach adopts a spatial hashing technique which virtually partitions the space where the cloth object locates into small cubes and stores the information of the particles being held in the cells with an integer array. With the data of the particles and the cells holding information of the particles, self-collision detection can be processed in a very limited cost in each thread launched in GPU regardless of the increase in the amount of particles. This method is capable of visualizing self-collision detection and response in real time with limited cost in accessing memory on the GPU. </p> <p>The idea of the proposed fast approach is extremely straightforward, however, the amount of memory which is needed to be consumed by this method is its weakness. Also, this method sacrifices physical accuracy in exchange for the performance.</p>

In this thesis, we will investigate the rapidly developing eld of computergraphics by giving an insight into the calculations behind the most im-portant topics in perspectives, shading and distance. We will delve intofrequently used shading algorithms and perspective transforms in areas ofcomputer science, architecture and photography, such as pseudo sh-eyelenses and wide-angle lenses.

Visualization is an important tool for presenting data to humans in an easy-to-understand manner. With new radar technology in development that can gather 3D atmosphere data, it opens up new possibilities for using 3D visualization tools to visualize the data, e.g, OpenSpace. OpenSpace is an open-source tool for visualization of the cosmos and universe. An evaluation of different rendering methods inside OpenSpace is evaluated to answer which method is most suitable for visualizing atmospheric 3D data. The data is in the format of HDF5 files and contains a list of beams with samples scattered along the beams, an algorithm is implemented to transform the beam data into a 3D volume which is used inside OpenSpace to be rendered. Tests are implemented to gather information on which parameter in the algorithm affects CPU execution time the most. The tests consist of executing the algorithm 100 times with different combinations of parameters to see which parameter has the largest effect on execution time, and a complexity analysis is calculated to evaluate the complexity of the algorithm. The results of the tests shows that the height of the volume affects execution performance the most on larger sizes. On small sizes, the difference between the different dimensions are insignificant. With the combination of height and smoothing, it slowed the execution time by a larger margin compared to width and smoothing or depth and smoothing. By implementing Volumetric ray casting and Point clouds as rendering methods, the results showed that both can visualize the data in real-time. Volumetric ray casting rendered with a clearer result in comparison to Point clouds, thus, Volumetric ray-casting is the preferred method to use when rendering atmospheric 3D volumes that is able to meet certain criteria.

<p>Digital image steganography is the process of embedding information withina cover image in  a  secure,  imperceptible,  and  recoverable  way.The  three  main  methods  of  digital  image steganography  are  spatial,  transform,  and  neural  network  methods. Spatial  methods  modify  the pixel  valuesof  an  image  to  embed  information,  while  transform  methods embed  hidden information within the frequency of the image.Neural network-based methods use neural networks to perform the hiding process, which is the focus of the proposed methodology.</p> <p>This  research  explores  the  use  of  deep  convolutional  neural  networks  (CNNs)  in  digital image steganography. This work extends an existing implementation that used a two-dimensional CNN to perform the preparation, hiding, and extraction phases of the steganography process. The methodology proposed in this research, however, introduced changes into the structure of the CNN and   used   a   gain   function   based   on   several   image   similarity   metrics   to   maximize   the imperceptibility between a cover and steganographic image.</p> <p>The  performance  of  the  proposed  method  was  measuredusing  some  frequently  utilized image metrics such as structured similarity index measurement (SSIM), mean square error (MSE), and  peak  signal  to  noise  ratio  (PSNR).  The  results  showed  that  the  steganographic  images produced by the proposed methodology areimperceptible to the human eye, while still providing good  recoverability.  Comparingthe  results  of  the  proposed  methodologyto  theresults  of  theoriginalmethodologyrevealed  that  our  proposed  network  greatly  improved  over  the  base methodology in terms of SSIM andcompareswell to existing steganography methods.</p>

Hand drawn ornamentation, such as floral or geometric patterns, is a tedious and time consuming task that requires much skill and training in ornamental design principles and aesthetics. Ornamental drawings both historically and presently play critical roles in all things from art to architecture; however, little work has been done in exploring their algorithmic and interactive generation. The field of computer graphics offers many algorithmic possibilities for assisting an artist in creating two-dimensional ornamental art. When computers handle the repetition and overall structure of ornament, considerable savings in time and money can result. Today, the few existing computer algorithms used to generate 2D ornament have over-generalized and over-simplified the process of ornamentation, resulting in the substitution of limited amounts of generic and static "clip art" for once personalized artistic innovations. Two possible approaches to computational ornamentation exist: interactive tools give artists instant feedback on their work while non-interactive programs can carry out complex and sometimes lengthy computations to produce mathematically precise ornamental compositions. Due to the importance of keeping an artist in the loop for the production of ornamentation, we present an application designed and implemented utilizing a user-driven global planning strategy, to help guide the generation of two-dimensional ornament. The system allows for the creation of beautiful organic ornamental 2D art which follows a user-defined curve. We present the application, the algorithmic approaches used, and the potential uses of this application.

The recent development of the impulse/summation approach for efficient B-spline computation in the discrete domain should increase the use of B-splines in many applications. Because we show here how the impulse/summation approach can also be used for constructing polynomials, the approach with a search table approach for the inverse square root operation allows an efficient shading algorithm for rendering an image in a computer graphics system. The approach reduces the number of multiplies and makes it possible for the entire rendering process to be implemented using an integer processor. In many applications, Chebyshev approximation with polynomials and splines is useful in representing a stream of data or a function. Because the impulse/summation approach is developed for discrete systems, some aspects of traditional continuous approximation are not applicable. For example, the lack of the continuity concept in the discrete domain affects the definition of the local extrema of a function. Thus, the method of finding the extrema must be changed. Both forward differences and backward differences must be checked to find extrema instead of using the first derivative in the continuous domain approximation. Polynomial Chebyshev approximation in the discrete domain, just as in the continuous domain, forms a Chebyshev system. Therefore, the Chebyshev approximation process always produces a unique best approximation. Because of the non-linearity of free knot polynomial spline systems, there may be more than one best solution and the convexity of the solution space cannot be guaranteed. Thus, a Remez Exchange Algorithm may not produce an optimal approximation. However, we show that the discrete polynomial splines approximate a function using a smaller number of parameters (for a similar minimax error) than the discrete polynomials do. Also, the discrete polynomial spline requires much less computation and hardware than the discrete polynomial for curve generation when we use the impulse/summation approach. This is demonstrated using two approximated FIR filter implementations. / Ph. D.

L'animation et le rendu sont deux domaines de recherche importants dans l'informatique graphique. L'occlusion ambiante (OA) est un moyen très répandu pour simuler l'éclairage indirect. Nous présentons une approche rapide et facile à mettre en œuvre pour l'approximation de l'occlusion ambiante de l'espace d'affichage. On calcule l'OA pour chaque pixel en intégrant les valeurs angulaires des échantillonneurs autour de la position du pixel qui pourrait bloquer l'éclairage ambiant. Nous appliquons une méthode séparable afin de réduire la complexité du calcul. La simulation des rides expressives du visage peut être estimée sans changer l'information géométrique. Nous avons construit un modèle de rides en utilisant une technique graphique qui effectue des calculs seulement dans l'espace d'affichage. Les animations faciales sont beaucoup plus réalistes avec la présence des rides. Nous présentons une méthode de cinématique inverse rapide et facile à mettre en œuvre qui s'appuie sur un modèle masse-ressort et qui repose sur les interactions de forces entre les masses. Les interactions de forces entre les masses peuvent être vues comme un problème de minimisation de l'énergie. Elle offre une très bonne qualité visuelle en haute performance de vitesse. En se basant sur notre méthode d'IK, nous proposons un modèle de synthèse des gestes corporels expressifs intégrés dans notre plateforme d'agents conversationnels. Nous appliquons l'animation de tout le corps enrichi par l'aspect expressif. Ce système offre plus de flexibilité pour configurer la cinématique expressive directe ou indirecte. De façon globale, cette thèse présente notre travail sur le rendu et l'animation en 3D. / Animation and rendering are both important research domains in computer graphics. We present a fast easy-to-implement separable approximation to screen space ambient occlusion.We evaluate AO for each pixel by integrating angular values of samplers around the pixel position which potentially block the ambient lighting.We apply a separable fashion to reduce the complexity of the evaluation. Wrinkle simulation can also be approximated without changing geometry information.We built a wrinkles model by using a modern graphics technique which performs computations only in screen space.With the help of wrinkles, the facial animation can be more realistic. Several factors have been proved, and wrinkles can help to recognize action units with a higher rate. Inverse kinematics (IK) can be used to find the hierarchical posture solutions. We present a fast and easy-to-implement locally physics-based IK method. Our method builds upon a mass-spring model and relies on force interactions between masses. Our method offers convincing visual quality results obtained with high time performance. Base on our IK method, we propose our expressive body-gestures animation synthesis model for our Embodied Conversational Agent (ECA) technology. Our implementation builds upon a full body reach model using a hybrid kinematics solution. Generated animations can be enhanced with expressive qualities.This system offers more flexibility to configure expressive Forward and Inverse Kinematics (FK and IK). It can be extended to other articulated figures. Overall, this thesis presents our work in 3D rendering and animation. Several new approaches have been proposed to improve both the quality and the speed.

Two hardware factors contributing to the overall image quality of digital CR Ts are display resolution and addressability. The relationship between these two factors and human performance was modeled by a metric of display quality, the Resolution Addressability Ratio (RAR), and investigated within the contexts of Word-Processing (WP) and Computer-Aided-Drafting (CAD) tasks. The findings indicate a perceptual limit to MTF bandwidth improvements, and significant differences iii display quality requirements between the two applications. The regression of image quality as a function of RAR metric values resulted in an r2 = 0.94 for the WP task and an r2 = 0.79 for the CAD task. These findings are discussed in terms of engineering guidelines for the design of CRT and flat-panel displays for applications which vary by the amount of the density of information in their typical displays.

Computing correspondences or maps between shapes is one of the oldest problems in Computer Graphics and Geometry Processing with a wide range of applications from deformation transfer, statistical shape analysis, to co-segmentation and exploration among a myriad others. A good map is supposed to be continuous, as-bijective-as-possible, accurate if there are ground-truth corresponding landmarks given, and lowdistortionw.r.t. different measures, for example as-conformal-as-possible to preserve the angles. This thesis contributes to the area of non-rigid shape matching and map space exploration in Geometry Processing. Specifically, we consider the discrete setting, where the shapes are discretized as amesh structure consisting of vertices, edges, and polygonal faces. In the simplest case, we only consider the graph structure with vertices and edges only. In this thesis, we design algorithms to compute soft correspondences between discrete shapes. Specifically, (1)we propose different regularizers, including orientation-preserving operator and the Resolvent Laplacian Commutativity operator, to promote the shape correspondences in the functional map framework. (2) We propose two refinement methods, namely BCICP and ZoomOut, to improve the accuracy, continuity, bijectivity and the coverage of given point-wisemaps. (3)We propose a tree structure and an enumeration algorithm to explore the map space between a pair of shapes that can update multiple high-quality dense correspondences.