Geological Wearing A Hat In The Graphics Clipping Algorithm And System Realization

Geological-hat is the lithological profile with the corresponding seismic profile of the same scale, which is established on the basis of information about geological surfaces, the exposed strata structural characteristics, and the lithology. The seismologists can be aware of the structural geology by the seismic profiles easily. For a long time, geological-hats mapping are done by manual work of seismologists, and, the lack of related computer drawing software and technology affects the production efficiency clearly. There is a key factor that makes this kind of automation method didn't come out: how to make the computer to be able to distinguish the closed area constituted by the surface-line and layer-line, and to fill with the correct lithology symbols. This is not a complicated problem to human's eyesight and intelligence; however, it is really hard for the computer to do the same work. The major reason for that is the so-called polygon clipping problem which aims to recognize the closed area formed by lines. This is also a classical problem of computer graphics which have not yet been fully solved by present. In this dissertation, a new"line clipping to block"method is proposed based on the Geological-hat and a new hole-polygon clipping algorithm is implemented .Our work is done by the research of existed two-dimensional clipping algorithm. Our major work lies on 5 aspects:1.Through the study of several classic clipping algorithms, we realize that the early line clipping algorithms are all based on a rectangular window, while the problem in practical applications are mostly irregular polygon, so there are some limitations in these methods. And the existed polygon clipping methods are always for some particular problems, so they are all lack of versatilities.2.We have analyzed the system requirements, and designed each functional module of the system based on the characteristics of geological mapping .Meanwhile, we have simplified the characteristics of block diagram with the regional geology, get the abstract geometric model and the corresponding calculation type, then focused on the analysis of the key point to draw geological-hats which is used as the clipping scenarios and conditions in the following steps. 3. We have designed a line clipping to block algorithm based on the clipping conditions and the polygon clipping is realized through the definition of"the relevant segments' basic unit" and the provision of the operation and rotation direction vector.4. A hole-polygon clipping algorithm is implemented based on the"line clipping to block"method. Through the work of setting the direction of hole-polygon boundaries, the adding of the effective intersection points to the right positions, the combination of the effective segments' directions and the computation of intersecting part and difference part of the two polygons, the blocks are figured out.5. A Geological-hat mapping system is developed with modular implementation approach and the features of each module. Our system is user-friendly and easy to operate.