Texte remanié de: Th. Univ.--Géomorphol. appl.--Strasbourg 1, 1990. / Résumé en anglais. Bibliogr. p. 296-307.

In this thesis, methods for texture mapping voxel based terrain of arbitrary topology, are studied. Traditional methods for generating terrain often use 2D height maps which has its limitations in topology, but often can rely on fast and simple planar projection for texture mapping. To generate terrain of arbitrary topology and support features like caves, overhangs and vertical cliffs, the terrain representation needs to expand from two dimensions and surface rendering to three dimensions and volumetric rendering, and also needs other, more elaborate methods for texture mapping. The initial part of the thesis recounts \emph{Marching Cubes}, the main method used for volumetric rendering, and also some basics on texture mapping. A survey reviews different related work on the area and lists some of the features. Some initial tests, to achieve texture mapping on arbitrary terrain, are performed and are explained and evaluated. These tests focus on partition the terrain into submeshes of similar directional faces, using the initial voxel grid as a natural boundary, and project each submesh to a planar texture space called \emph{charts}. The texture of each chart is defined by the highest resolution of each submesh and all charts are stored in one \emph{texture atlas}. The charts then represent the texture used for all different resolutions of the submesh. The method results in gaps in the final texture due to mismatch occurring from the different mesh resolutions. To avoid the mismatch each chart is mapped to fixed shapes, namely triangles or quads. This solves the problem with gaps along chart boundaries but instead introduce heavy distortion in the texture due to stretching and resizing. Some tests have also been performed on editing the underlying scalar field directly by identifying and avoiding some unwanted cases, and creating a simpler mesh.

Thesis (M.S.)--University of Wisconsin--Stevens Point, 2007 / Includes bibliographical references.

No description available.

It is a time consuming task to generate textures for large 3D terrain surfaces in computer games, flight simulations and computer animations. This work explores the use of cellular automata in the automatic generation of textures for large surfaces. I propose a method for generating textures for 3D terrains using various approaches - in particular, a hybrid approach that integrates the concepts of cellular automata, probabilistic distribution according to height and Wang tiles. I also look at other hybrid combinations using cellular automata to generate textures for 3D terrains. Work for this thesis includes development of a tool called "Texullar" that allows users to generate textures for 3D terrain surfaces by configuring various input parameters and choosing cellular automata rules. I evaluate the effectiveness of the approach by conducting a user survey to compare the results obtained by using different inputs and analyzing the results. The findings show that incorporating concepts of cellular automata in texture generation for terrains can lead to better results than random generation of textures. The analysis also reveals that incorporating height information along with cellular automata yields better results than using cellular automata alone. Results from the user survey indicate that a hybrid approach incorporating height information along with cellular automata and Wang tiles is better than incorporating height information along with cellular automata in the context of texture generation for 3D meshes. The survey did not yield enough evidence to suggest whether the use of Wang tiles in combination with cellular automata and probabilistic distribution according to height results in a higher mean score than the use of only cellular automata and probabilistic distribution. However, this outcome could have been influenced by the fact that the survey respondents did not have information about the parameters used to generate the final image - such as probabilistic distributions, the population configurations and rules of the cellular automata.

Dažnai kompiuterinės grafikos taikymuose labiausiai visos scenos atvaizdavimo greitį įtakoja kraštovaizdžių atvaizdavimas. Darbe nagrinėtas vienas iš dviejų greičiausių šiuolaikinių kintamo detalumo kraštovaizdžių atvaizdavimo algoritmų – geomipmap. Šis algoritmas pasirinktas dėl platesnio pritaikomumo, didesnio algoritmo lankstumo ir šiai dienai dažnai didesnio greičio lyginant su jo varžovu geoclipmap. Algoritmo idėja – panaikinti kas antrą viršūnę iš vaizduojamųjų sąrašo, pereinant prie žemesnio detalumo lygio, taip sudarant galimybę laikyti visą geometriją keliuose nekintančiuose viršūnių ir indeksų buferiuose. Darbe pasiūlyta algoritmo optimizacija išnaudoja iš aukščių žemėlapio generuojamų kraštovaizdžių apatinę ribą. Pagrindinė idėja – nevaizduoti visų šioje riboje esančių trikampių, vėliau visus atsiradusius tarpus uždengti naudojant vieną plokštumą, ištemptą per visą kraštovaizdį. Nors optimizacijos efektyvumas priklauso nuo kraštovaizdžio formos ir negalima vienareikšmiškai įvertinti atvaizdavimo pagreitėjimo bendru atveju, nagrinėtose scenose užfiksuotas didelis našumo padidėjimas, aiškiai vertingas, net jei pasireikštų tik labai retais atvejais. Darbe taip pat parodoma, kad našumo padidėjimas iš tiesų galimas daugelyje scenų. / Often the bottleneck in the real-time 3D rendering applications is the rendering of a terrain. Geomipmap algorithm is analyzed here as it is one of the best terrain rendering algorithms known. It is much more versatile and flexible in comparative to geoclipmap and still often outperforms its main rival. The idea is to eliminate every other vertex in order to get a lower level of detail, thus having all the geometry in several immutable vertex and index buffers. An optimization is proposed that utilizes the lower bound of terrains generated from a heightmap. The idea is not to render the triangles that are exactly on the lower bound of a terrain and to cover all the eliminated triangles with a single plane. Even though the effectiveness of the optimization is highly dependent on the exact form of the terrain, the high performance gain observed in the analyzed scenes is valuable even if it would only occur in very rare cases. It is shown that the performance gain can actually be observed in quite a variety of scenes.

UNSTABLE was a field project in the summer of 2008 to better understand the large-scale and mesoscale forcings of summer storms. This thesis objective is to better understand boundary layer characteristics and convective environments in the Alberta foothills. Three sub-objectives are designed to address the overall thesis goal: (1) Characterize the daily evolution of the boundary layer during different convective regimes, (2) distinguish conditions between days with deep, shallow and no convection, and (3) to illustrate how targeted soundings can be useful for severe storm prediction. Non-convective days exhibited a warmer atmospheric column. Days with shallow convection exhibited a mid-level inversion. Deep convective days commonly displayed unstable low-levels and cooler upper levels, deep low-level moisture and the mountain-plains circulation. When compared to the pre-existing operational upper air network, mobile UNSTABLE soundings better captured the near storm environment of two tornadic events in terms of available instability and shear profiles.

Thèses (M.Sc.A.)--Université de Sherbrooke (Canada), 2004. / Titre de l'écran-titre (visionné le 21 juillet 2006). Publié aussi en version papier.

Computer-aided tools appropriate to architecture, engineering and construction have been Summarised, including digital terrain modelling (DTM), computer-aided design and draughting (CADD) and database management systems (DBMS). DTM and CADD techniques have been applied to simulating the hydraulic filling of tailings, or mine waste dams. A relational DBMS was used to structure and manage filling and terrain data relevant to hydraulic tailings disposal at the Wheal Jane mine in Cornwall.

Titre de l'écran-titre (visionné le 11 avril 2023) / La sismicité représente un enjeu majeur pour l'industrie minière. Elle affecte la sécurité du personnel minier, des opérations et la rentabilité des mines. Lorsqu'il est impossible de minimiser suffisamment l'aléa d'un coup de terrain, des mesures de mitigation du risque doivent être implantées. Une de ces mesures est l'utilisation de systèmes de soutènement bonifiés souvent qualifié de système de soutènement dynamique. La conception de systèmes de soutènement dans les mines subissant des conditions dynamiques est souvent basée sur l'expérience et les connaissances acquises à chaque mine, ce qui rend leur méthode spécifique au site et à ses conditions. Stacey (2012) a conclu que comme la capacité dynamique des systèmes de soutènement ainsi que la demande dynamique induite par les évènements sismiques ne pouvaient être quantifié de façon fiable, il était impossible d'utiliser les méthodes de conception de support de terrain traditionnelles pour déterminer les besoins en systèmes de soutènement. Ce mémoire vise à développer une meilleure compréhension de l'influence de la combinaison des facteurs de mouvement de terrain (GMFs) et diverses conditions géotechniques sur la fiabilité de stratégies de soutènement sujettes à des conditions dynamiques. La performance de dix stratégies de soutènement étudié pour un intervalle de GMF exprimée comme une fonction de la magnitude de l'évènement sismique et la distance entre la source sismique et le dommage. Le critère de performance est la survivabilité du système de soutènement (i.e., aucune chute de terrain, mais une réhabilitation peut être requise). Un index de fiabilité a aussi été développé pour classer la fiabilité de la performance. Les résultats sont montrés dans une matrice de survivabilité qui sera contributoire dans la sélection de systèmes de soutènement dans les mines souterraines soumises à des conditions dynamiques. / Seismicity represents one of the major threats of the mining industry. It affects the mining personnel safety, the operations, and the profitability of the mine. When it is impossible to eliminate the probability of occurrence of a major seismic event, some measures need to be implemented to reduce the probability of seismically induced rockfalls (rockbursts). This is generally achieved with the installation of enhanced ground support systems, also often referred to as dynamic ground support systems. The design of (dynamic) ground support systems in mine facing rockburst-prone conditions is often based on the experience and knowledge acquired at each mine, which made their methods specific to their conditions. Stacey (2012) concluded that since the dynamic capacity of ground support systems and the demand from seismically induced dynamic loading cannot be reliably quantified, then "...a clear case of design indeterminacy" results, making it "...impossible to determine the required support using the classical engineering design approach". This master's thesis aimed at developing a better understanding of the influence of combinations of ground motion factors (GMFs) and various geotechnical conditions on the reliability of numerous ground support strategies subjected to dynamic loading conditions The performance of ten ground support systems strategies have been investigated for a range of GMF expressed as a function of the seismic event magnitude and distance between the seismic source and damage. The performance criterion is the survivability of the ground support system (i.e., no fall of ground, although rehabilitation may be required). A reliability index was developed to classify the reliability of the performance. Results are shown as a survivability matrix, which will be used to assist in the selection of ground support systems in underground mines facing rockburst-prone conditions.