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.

Hurricane Matthew (2016) was a category 5 hurricane that interacted with remote terrain over northern South America in the early stages of its life cycle. Because tropical cyclone (TC) precipitation and convection are known to be crucial factors in the understanding and forecasting of TC intensity, this study investigates how this terrain impacted Hurricane Matthew's rainband structure. Remote terrain is hypothesized to play a role in the strength of TC rainband convection by modifying the thermodynamic environment such that subsiding dry air advects over an extremely moist ocean surface layer leading to increased moist static instability. To investigate this hypothesis, this study utilizes the Advanced Research Weather and Research Forecasting Model (WRF-ARW) to create a high-resolution (2-km horizontal grid spacing) control simulation (CTL) of Hurricane Matthew and a second experimental simulation with a 50% reduction of terrain height over the topography of northern South America (T50). This study focuses on a particular convective rainband positioned downstream of the terrain that displayed prolonged robust convection during the initial stages of Hurricane Matthew's life cycle. Results indicate that characteristics of this robust rainband are consistent with prior research on an inner core rainband called a principal rainband. This rainband does not display differences in intensity in the two simulations but is located closer to the TC center and more persistent in the control simulation. In the region downstream of the topography, significantly (p < 0.05) drier conditions exist in the control simulation, which is consistent with the hypothesis that downslope motion would lead to a drier air mass. TC structural changes are also apparent, with a weaker TC in the reduced topography simulation. This research emphasizes the potentially important role of terrain distant from the TC center with possible influences on TC rainband convection and warm core structure. Conclusions of this research are limited due to the small sample size of a single case study. An ensemble modeling study and additional cases are needed for a more thorough conclusion on the impact of remote terrain on TC structure. / Master of Science / Predicting the intensity of hurricanes remains a monumental challenge for hurricane forecasters. Many factors can influence the intensity of hurricanes, including the strength, frequency, and spatial distribution of hurricane rainbands (band of precipitation). The hypothesis for this study is that terrain distant from the hurricane center can alter the hurricane environment and cause more frequent and stronger rainbands to form. To assess this hypothesis, I use a weather model to simulate Hurricane Matthew (2016) while it was interacting with remote terrain over northern South America on September 30 - October 1, 2016. Then I use the same model, but with terrain height reduced by 50% over northern South America and analyze the similarities and differences in the hurricane structure and rainband patterns. The results of this study suggest that terrain did not alter the peak rain rates in the hurricane rainbands but may have caused more frequent, widespread, and prolonged precipitation. Also, differences in hurricane structure were apparent when comparing the two model simulations. The reduced terrain simulation produced a weaker hurricane, lending some evidence to support the hypothesis that terrain may have played a role in altering the hurricane structure. These results demonstrate the potential importance of distant terrain on forecasting hurricane precipitation and intensity.