Research On Several Graphics Algorithms In The Field Of The 3D Geological Modeling

With the rapid development of the geological modeling and graphical analysis technology ,the problem that how to make the graphical technology to act on the software of the 3D geological modeling,which can play a significant role in the description and evaluation of the mineral and oil and gas resources, is worthy of study .The following three problems are often proposed in 3D geological modeling.Firstly, How to quickly describe the internal structure of the geological model?Secondly, How to reasonably avoid the collision between two geological models during the human-computer interaction of the 3D geological modeling software?Thirdly, How to accurately select the interested part of the geological model in the 3D geological modeling software?It is abviously that these three issues are greatly helpful for the description and evaluation of the mineral and oil and gas resources.In order to solve above problems, We propose three 3D graphics algorithms by using the arbitrary polyhedron instead of the various forms of the geological models.Firstly, the slice of polyhedron algorithm,which based on the intersection of the surfaces,can fastly and accurately get the profile of arbitrary polyhedron(including concave polyhedron) through two steps.The first step is the intersection computation between the cutting plane and the every surface of the polyhedron.The second step is to track the intersection lines to form the final result.Secondly,the collision detection algorithm,which based on the intersection of the surfaces and the judgment of the position relationship between point and polyhedron, can fastly and accurately detect the case of the collision between two arbitrary polyhedron (including concave polyhedron) through two steps.The first step is to infer whether the two polyhedral models intersect by judging whether there is the intersection between the boundary polygons of the polyhedral models.If there is no intersection,between the two polyhedrons, the second step is to infer whether there is the including relationship between the two polyhedrons by judging the position relationship between the point and the polyhedron. Thirdly, the 3D clipping algorithm,which based on triangle polyhedron,can fastly and accurately achieve selecting interesting part of the arbitrary polyhedron(including concave polyhedron) by arbitrary polyhedron window. The core idea of this algorithm is the clipping between each interface of the polyhedron window and the triangle polyhedron which will be clipped to one or several triangle polyhedrons.The correctness and effectiveness of those algorithms are proved through programming the algorithm.