141 research outputs found

    Modeling of erosion impact on geometric objects

    Get PDF
    Simulace eroze je důležitým problémem v oblasti počítačové grafiky. Nejvýznamnějšími erozními procesy v přírodě jsou zvětrávání a hydraulická eroze. Mnoho metod se těmito problémy zabývá, ale většinou jsou tyto metody založeny na výškových mapách nebo volumetrických datech. Výškové mapy neumožňují simulaci složitých plně trojrozměrných scén, zatímco volumetrická data mají vysoké paměťové nároky. Tato disertační práce zkoumá výhody reprezentace erodovaných objektů pomocí trojúhelníkových sítí a navrhuje řešení problémů, které vznikají v důsledku použití této datové struktury. Trojúhelníkové sítě se ukázaly být vhodnou datovou strukturou pro použití při simulaci eroze díky jejich adaptivitě a možnosti modelovat složité konkávní prvky scény. Použití trojúhelníkových sítí však přináší nové problémy, například problém vzniku nekonzistence sítě v důsledku silné eroze nebo problém simulace složitých scén složených z více materiálů. Tato práce zkoumá zmíněné problémy a navrhuje jejich možná řešení.ObhájenoErosion simulation is an important problem in the field of computer graphics. The most prominent erosion processes in nature are weathering and hydraulic erosion. Many methods address these problems but they are mostly based on height fields or volumetric data. Height fields do not allow the simulation of complex fully 3D scenes while the volumetric data have high memory requirements. This thesis explores the advantages of representing the eroded objects as triangular meshes and proposes solutions to problems that arise due to the use of this data structure. Triangular meshes prove to be an advantageous data structure for erosion simulations due to their adaptivity and the possibility to model complex concave features. However, the use of the triangular meshes brings new problems to the erosion simulation, such as the problem of creation of an inconsistency in the mesh due to heavy erosion or the problem of simulation of complex scenes composed of multiple materials. This thesis explores these problems and suggests possible solutions

    User Conference 2013

    Get PDF

    Proceedings of the XXVIIIth TELEMAC User Conference 18-19 October 2022

    Get PDF
    Hydrodynamic

    A Novel, Generic Approach To Simulate Bank Retreat In Alluvial River Channels

    Get PDF
    Despite the importance of bank erosion in rivers, most computational fluid dynamics (CFD) models have limited capacity to examine bank retreat and channel-floodplain interactions, as they lack bank stability algorithms and ignore vegetation effects. This research seeks to develop a numerical model to improve our understanding of key properties of bank material and vegetation cover with respect to lateral erosion in river meanders at intermediate spatial (5−10 meander bends) and temporal (2−3 years) scales. Following a comparison of six different morphodynamic models for three sinuous laboratory configurations, the CFD model TELEMAC-2D was chosen to receive a newly developed bank retreat module that respects geotechnical principles and integrates spatial analysis concepts. It was tested against morphological datasets from two contrasted river reaches, the semi-alluvial Medway Creek (Ontario) and alluvial St. François River (Quebec). Statistical analysis, combined with the use of machine learning algorithms, demonstrate that the coupled model is able to fit observed bank retreat location and extent. Some local disagreement with observations along Medway Creek seems associated with the heterogeneity of soil material and stratigraphy, and in vegetation cover present at the field site. The coupled model was also used to identify key geotechnical parameters and optimal parameter values for the studied reaches. An epistemological reflection on the purpose of modelling in fluvial geomorphology leads to the conclusion that the primary model strength lies in its ability to provide explanations on bank retreat mechanisms. Further research should seek to test more thoroughly morphodynamic modelling in complex geomorphological environments

    Visual Techniques for Geological Fieldwork Using Mobile Devices

    Get PDF
    Visual techniques in general and 3D visualisation in particular have seen considerable adoption within the last 30 years in the geosciences and geology. Techniques such as volume visualisation, for analysing subsurface processes, and photo-coloured LiDAR point-based rendering, to digitally explore rock exposures at the earth’s surface, were applied within geology as one of the first adopting branches of science. A large amount of digital, geological surface- and volume data is nowadays available to desktop-based workflows for geological applications such as hydrocarbon reservoir exploration, groundwater modelling, CO2 sequestration and, in the future, geothermal energy planning. On the other hand, the analysis and data collection during fieldwork has yet to embrace this ”digital revolution”: sedimentary logs, geological maps and stratigraphic sketches are still captured in each geologist’s individual fieldbook, and physical rocks samples are still transported to the lab for subsequent analysis. Is this still necessary, or are there extended digital means of data collection and exploration in the field ? Are modern digital interpretation techniques accurate and intuitive enough to relevantly support fieldwork in geology and other geoscience disciplines ? This dissertation aims to address these questions and, by doing so, close the technological gap between geological fieldwork and office workflows in geology. The emergence of mobile devices and their vast array of physical sensors, combined with touch-based user interfaces, high-resolution screens and digital cameras provide a possible digital platform that can be used by field geologists. Their ubiquitous availability increases the chances to adopt digital workflows in the field without additional, expensive equipment. The use of 3D data on mobile devices in the field is furthered by the availability of 3D digital outcrop models and the increasing ease of their acquisition. This dissertation assesses the prospects of adopting 3D visual techniques and mobile devices within field geology. The research of this dissertation uses previously acquired and processed digital outcrop models in the form of textured surfaces from optical remote sensing and photogrammetry. The scientific papers in this thesis present visual techniques and algorithms to map outcrop photographs in the field directly onto the surface models. Automatic mapping allows the projection of photo interpretations of stratigraphy and sedimentary facies on the 3D textured surface while providing the domain expert with simple-touse, intuitive tools for the photo interpretation itself. The developed visual approach, combining insight from all across the computer sciences dealing with visual information, merits into the mobile device Geological Registration and Interpretation Toolset (GRIT) app, which is assessed on an outcrop analogue study of the Saltwick Formation exposed at Whitby, North Yorkshire, UK. Although being applicable to a diversity of study scenarios within petroleum geology and the geosciences, the particular target application of the visual techniques is to easily provide field-based outcrop interpretations for subsequent construction of training images for multiple point statistics reservoir modelling, as envisaged within the VOM2MPS project. Despite the success and applicability of the visual approach, numerous drawbacks and probable future extensions are discussed in the thesis based on the conducted studies. Apart from elaborating on more obvious limitations originating from the use of mobile devices and their limited computing capabilities and sensor accuracies, a major contribution of this thesis is the careful analysis of conceptual drawbacks of established procedures in modelling, representing, constructing and disseminating the available surface geometry. A more mathematically-accurate geometric description of the underlying algebraic surfaces yields improvements and future applications unaddressed within the literature of geology and the computational geosciences to this date. Also, future extensions to the visual techniques proposed in this thesis allow for expanded analysis, 3D exploration and improved geological subsurface modelling in general.publishedVersio
    corecore