Research Of 3D Seismic Data Visualization Based On PC

Seismic survey goes through 2D and 3D, up to now, 4D survey methods. This progress has put forward challenges to the traditional 2D seismic interpretation, which did not make the best of information of 3D or 4D seismic data sets, so old interpretation methods must lead to make mistakes of analyzing and deciding rock properties and subsurface structures, that is, old interpretation methods are not effective. So the true 3D interpretation of seismic data is important, which depends on the virtual reality and scientific visualization technologies.This paper discusses the rendering of seismic data using virtual reality and scientific visualization technologies. These technologies can display distributions and features of subsurface horizons very straightly. We particularly discuss the classification of data sets, model of visualization, horizon segmentation and visualization methods, based on discussion above, finally we constitute a PC-based seismic data interpretation system.Horizon segmentation is the key step of analyzing subsurface structures and rock properties. According to links among voxels, we give a based-seed segmentation method, which is a kind of rude segmentation method. In order to improve the precision of segmentation, we make most use of the local information of a voxel and give region-growing segmentation based on the local information. Depending on the built-in features of seismic data, we also discuss definitions of the consistent function of segmentation. For segmentation of special seismic events, we bring forward the "center-voxel" method, which simplifies the 3D segmentations into 2D segmentations, advances the speed of segmentation.During the visualization, the classification and visualization model is very important. In this paper we use the variable-density emitter model. Voxels' intensities are relative to values of voxels' property, for example, the amplitude and coefficient. These properties can be displayed using different colors or gray levels. Definition of the transfer function of opacity is most difficult, because we know nothing about the seismic data before rendering. In order to solve this problem, we give a transferfunction definition method: dual domain transfer function definition, which overcomes the trying and rendering and trying definition method' s disadvantage.Now most of rendering methods are based on medical data, which are small and relatively fixed features of human body. But seismic data is very large, features of subsurface are not known firstly and very irregular, these differences make rendering methods based on medical data are not adapted to seismic data. So we need to simplify old rendering methods or give a new kind of rendering methods. This paper discusses four main rendering methods: ray casting, splatting, shear-warp and texture-based rendering, by analyzing we conclude that only the texture-based rendering algorithm is fit for the visualization of seismic data, which makes the interactive rendering true. But the texture-based rendering algorithm is most dependent on the capacities of graphical card, so we bring forward a new rendering algorithm - iso-value voxel projection algorithm (IVP), which can be used on PC, does not depend on graphical card. This algorithm makes a voxel corresponding to the OpenGL POINT element, so volume rendering is simplified into surface rendering, but the main disadvantage is the low definition. As far as the visualization of seismic data is concerned, this definition is enough.Finally, a PC-based seismic data interpretation system is realized. We also give stereo display of seismic data, which makes interpreters straightly decide subsurface spatial relations. This system also combines traditional 2D section' s interpretation with 3D volume rendering. The coherence cube is also visualized, so we can analyzed and decide complex faults and other non-constructional events, for example, channels and fan-deltas.