Research And Implementation Of 3D Open Pit Data Modeling Algorithm

At present, Visualization in Scientific Computing is a hot direction in computer graphics. With the development of 3D Geographic Information System (3D GIS),3D data modeling as the core and critical functions of Visualization in Scientific Computing is widely used in various fields of natural sciences and engineering projects. In the aspect of geological and mining, 3D data modeling is widely used in DEM (Digital Elevation Model), mine surface modeling, and 3D open-pit modeling. Based on analyzing the characteristics of various data model, this thesis studies around two problems, the first is the algorithm of 3D open-pit data modeling, which includes building up the interactive wireframe model and solid surface model based on wireframe model, the second is 3D solid Boolean algorithm based on TIN (Triangulated Irregular Network).In the aspect of 3D data modeling algorithm, this thesis proposes 3D wireframe modeling algorithm and 3D solid modeling algorithm which is under 3D interactive and virtual environment. The wireframe modeling algorithm projects the 3D open-pit wireframe form 3D to 2D by using the method plane parameterization, and uses the scaling algorithm of polygon combined with parameter control, which can generate 3D open-pit wireframe model in real time. And the geological researchers can set the parameters and browse the effect of 3D model under 3D interactive and virtual environment, and modify the parameters in real time to achieve the best design results. In the aspect of 3D solid modeling algorithm, this thesis also uses the method of plane parameterization to project the 3D open-pit wireframe form 3D to 2D, and presents the new algorithm which is CDT (Constaint Delaunay Triangulation) based on Minimum Search Circle to quickly model. And this algorithm can quikly generate 3D solid model.In the aspect of 3D solid Boolean based on TIN, this thesis presents an improved, fast and stable Boolean algorithm. Firstly, the improved algorithm combined with hierarchical bounding volume (HBV) algorithm uses a structure of hybrid hierarchical bounding volume (HHBV) for rapid detection of intersecting triangles and calculate intersecting lines which can avoid unnecessary intersection computation. And then, the algorithm fully analysises the causes of calculation error due to the precision in 3D Boolean calculation, and uses the improved spatial triangle intersection algorithm of discrete cross-lines, and re-triangulation of the single triangle. Finally, through building up the topological relationship of cross-lines and inteesected triangles for tracking and extraction and classifying, combining the local area, the algorithm can rapidly realize the accurate Boolean operations for 3D mesh model. The algorithm can solve various special examples, and skillfully deal with the coplanar cases of intersecting triangles. The algorithm can not only rapidly solve the Boolean operations of the closed solid models, but also the Boolean operations of the closed solid model and the open solid model.The algorithms are implemented in practical project, and obtain rather satisfactory result in experiment and in practice. The software can effectively, rapidly and stably deal with the special cases.