Research On Generation And Real-time Visualization Of Geological Strata Based On The Geodesic Lines

In recent years, the techniques of computer modeling and rendering are more and more used in the geological exploration such as oil, coal bed methane. The modeling of the strata grid takes an important part in the process of geological exploration. Based on the surface modeling of the strata data, it needs to construct an intuitive, complete, clear and layered three-dimensional (3D) geological visualization model. However, many algorithms of the strata grid generation still have many shortcomings, such as:the lower degree of automation, the bad desired effect especially on the surfaces, helpless of the complex models. How to quickly generate the grid that has good surface characteristics and can reflect the overall structure of the strata has become a difficulty in the geological modeling. In addition, as the large scale of strata grid, the algorithm that uses regular methods will be subject to the constraints of the hardware.It is often difficult to draw such a large-scale data real time in the process of visualization of the geological data.To address the problem above, the main contributions of this thesis is as follows:1) An algorithm of computing geodesic between two vertices is proposed. On the basis of the virtual source algorithm for geodesic, a new algorithm of computing geodesics in the discrete triangle grid is proposed and proved. The experimental results show that the improved geodesic algorithm can adapt to the computing needs of large-scale grid data, and can obtain more accurate geodesics.2) An algorithm of generating the hexahedral strata grid is proposed based on the geodesics. Firstly, the feature vertices of the strata can be calculated by the geodesic path of the grid. Under the constraints of the surface vertices, the hexahedral nodes that have a uniform distribution and reflect the surface change trends in the location can be generated with the method of revise. Finally, a structured hexahedral grid will be produced. Experimental results show that the structured hexahedral grid is better to reflect the characteristics and meet the requirements of the strata data. By the analysis, inference and interpretation of the structured hexahedral grid, geological researcher could get more accurate results.3) A method of scheduling the large-scale strata grid data and real-time visualization is proposed and implemented. On the basis of the structured hexahedral grid, a data scheduling method and a visualization strategy of mass strata data is presented. By using the multi-resolution strategy which is based on the out-of-core, the thought of the block and the level of detail (LOD) technology, a prototype system has come true. The objectives of rapidly extracting bisect data and real-time rendering have achieved, and the performance of user interaction has been improved too.