An Interactive 3D Geological Modeling System With "Marching Cubes" As A Kernel Algorithm

The study of the theory of three-dimensional geological modeling is one of the fundamental works in3DGIS. for 3D geological modeling is a very important component of 3DG1S. It is the foundation andkernel of 3D geosciences visualization software and 3D geosciences information system.Due to the complexity of geological conditions, the theory and techniques of 3D geological simulationare still in the phase of research, many problems are still unresolved. These days, in the field of miningand geophysics, 3D geological simulation has entered the practical stage in the west, having someexperienced software. But in our country there is no such software of our own.Different methods of modeling decide different data structure and the operations that can be carried out,this dissertation classifies the existed geological models into two general types: the volume-filling modeland the boundary model. The volume-filling model is used for the heterogeneous geological bodies andthe boundary model used for the homogeneous geological bodies.In fact, all of the geological bodies are complicated and heterogeneous. While simulating geologicalobjects, simplification must be done. At present, using some homogeneous geological bodies torepresent the heterogeneous geological bodies is a practical and efficient method.This dissertation use the boundary model representing homogeneous geological body, since the softwarefinished this time is focused on the editing of model and the volume-filling model representingheterogeneous geological bodies is completely not suitable for this situation.In the period of 8n 5-year-plan, we finished a software of computer aided exploration system namedPandaCAEX. This system used the boundary model represented by polyhedron, and successfullyachieved the interactive modeling of 3D geological model and the inversion of gravity and magneticanomalies. This system reached the advanced international standard in some aspects and acquired the 2ndlevel award of science and technology from the ministry of geology. The main contribution of thesystem to the 3D geological modeling is the original creation of the technique so called "rubbermembrane" aimed to overcome the difficulty of interactive modeling of 3D geological model. Using thistechnique, users can easily make arbitrary shaped 3D geological model interactively.The design target of PandaCAEX is to carry out the inversion of 3D gravity and magnetism of metalmine model, so the modeling algorithm is aimed to animate the isolated complex geological body, at thattime, that is thought to be OK. Therefore this modeling algorithm has no the ability to deal with adjoinedmodels, the adjoined models will has unwilling overlap.But not all of the geological models are isolated, the metal mine model has adjoining situation, and themore important situation is the existence of layer geological body. PandaCAEX system has no anyability to deal with such situation, for the layer geological body is some adjoined geological bodyindeed.The purpose of this dissertation is solving the overlapping problem in PandaCAEX when modelsadjoined, it creates a new modeling technique that can represent both the metal mine model and the layermodel, the most important is that it completely solve the overlapping problem.The key of the algorithm is the setup of an accessory 3D grid in the defined 3D space. Models can havesome relationship depending on the grid, resulting that the overlap problem be solved. The coretechniques are the rasterization of polyhedron and the polyhedronization of the 3D raster. Among these techniques, the rasterization of polyhedron is the direct extension of the rasterization of polygon in 2D space, the major creation of this dissertation is the solution of the polyhedronization of the 3D raster. Marching Cubes is the technique that extracts isosurface from 3D raster in scientific visualization. This dissertation modifies it, and then uses the modification to ma...