Coal seam modeling based on hexahedron grid and triangulation algorithm for real-time visualization

3D coal seam modeling and visualization are two key parts of digital mining application. In this article, we proposed a convenient modeling method based on double-layer regular grid data (elevation grid and thickness grid), and developed a less redundant triangulation algorithm on the basis of a 3D irregular hexahedron. This grid-based molding fit the features of coal seam and general data producing approaches, boreholes interpolating and geophysical prospecting. The core of the algorithm is a virtual irregular hexahedron, whose bottom face is created by elevation grid and top face comes from an elevation grid plus corresponding thickness grid. The author summed up 5 different types of hexahedron for representing different situations in real coal seam and being as checking conditions to make sure integrity of the algorithm. Special areas in grid, where the values are invalid digital, express the collapse columns and outside areas in coal seam. Based on the layout of valid points in a hexahedron and the location of a grid data block in a coal seam, an iterating algorithm using hexahedral cell has been proposed, that dynamically fetch the 3D grid data from database only once in every real-time rendering. Each face of hexahedral cell is subdivided into seamless triangles in different approach according to the location of valid points. This paper concludes that the model combines the advantage of easy rendering by triangles and high accessibility of grid data; the algorithm can efficiently solve the problem of model reconstruction caused by database update with less redundancy.