Study On The Technology Of 3D Engineering Geological Modeling And Visualiztion

The geometry, topology, and attributes of the geological objects can be represented and understood directly in 3D spatial perspective by the technology of 3d engineering geological modeling and visualization, which is based on the technology of computer and visualization, and is important for engineering decision and geology data management, so it has been the interdisciplinary frontier and hot point of geosciences and information science. Some key problems of 3d geological modeling are discussed in this paper, which are mainly including several aspects listed below.1. The 3d data model which is well adapted to modeling complex geological structures Boundary based topological models (BRep) has become the standard way to represent the topology of 3d geological objects on computer.Recently, more robust and rigorously defined approaches to boundary based topological representation of complex objects have been developed based on combinatorial maps, which is the 3-dimensional generalized map (3GMap), and it has extensive capabilities for non- manifold topological representation. Firstly, the theory of 3GMap is presented and compared to other existing boundary representation techniques, such as the winged-edge, half-edge, and radical-edge data structure. Then, some extensions are derived from 3GMap for the boundary topology representation of geological structures, which is so-called 3-dimensional geological generalized map (3GGMap). The 3GGMap is proved to be well adapted to geological modeling, which has many advantages than other BRep data models. The few and clear basic concepts that 3GGMap are based on are intuitive and easy to deal with for application programmers and end users, and the topological kernels are easy to implement. The other major advantage is the possibility to represent the micro- and macro topology of geomodels in one consistent data structure with an algebraic foundation, and it is easy to distinguish between topology and geometry.An objected-oriented design of topological kernels and implementation in the C++ programming language are proposed in this paper.2. The geology surface fittingThe triangulated irregular network is used to fit the geology surface, such as the formation interfaces, faults, terrene surface, overburden surface, and so on. And the accurate and smooth geology surface can be modeled by different methods for different data sources based on the Delaunay and constrained Delaunay triangulation algorithm, in fact, the incremental algorithm is adopted in this paper. The survey data can be made the best of to build the geology surface model by these methods.3. The fast algorithm for cutting and intersecting between geology surfacesThe fast and robust algorithm for cutting and intersecting between geology surfaces represented by triangulated irregular network is built, by introducing the collision detection technique that is widely used in games and computer graphics. 4. The technique for 3d geological modeling in automatic wayIn order to build the 3d geological model in automatic way, two aspects are discussed in this paper. Firstly, the concept of geological evolution graph (GEG) is introduced in this paper, which is a"geological pilot"for the process of 3d geological modeling. Therefore, it is possible to take advantage of the specificity of geological structures to pilot the automatic building of a 3D consistent geological model; and this can be done by putting the various surfaces of the model into place one after another in a definite order taking into account their intersections at each step by reading instruction from the GEG. Secondly, the cutting rules for the geological surfaces are defined according to contact relationship between intersecting formations, and the boolean operations between the intersecting geological surfaces can be done by computer in automatic way.5. The developments and applications of the 3d geological modeling systemA primitive platform so-called 3DGeoModeller for 3d geological modeling and visualize- tion is developed by using Visual C++6.0 programming language and object-oriented visual interface-Visual Toolkits (VTK). The system has some functions for regional geological data management, 3D modeling, 3D geological information visualization, and basic analysis based on the 3d geological model.At last the system is used in highway slope and hydropower projects 3D geological modeling and analysis, the results show the feasibility and validity of the basic theories presented in this paper.