3D Modeling Methods

In the process of 3D geologic body modeling, the construction of the surface model relies on the generation of digital terrain model (DTM), and the construction of the subsurface model is the first generation of three-dimensional wireframe for each geologic body, and then connected to the solid for certain Boolean operations.

(1) Digital Terrain Model (DTM)

Digital Terrain Model (DTM) is a simple statistical representation of a continuous ground by selecting x, y and z coordinate points using an arbitrary coordinate system. Or, DTM is a digital representation of the morphological attribute information of the terrain surface, a digital description with spatial location features and terrain attribute features.

(2) 3D wireframe model

The construction of 3D wireframe model mainly adopts the Voronoi diagram and Delaunay triangle algorithm in the TIN technology (irregular triangular network model). The basic principle is as follows: firstly, based on the collected geological survey and other information to determine the spatial relationship of the geological structure surface, the use of spatial intersection to get the geological structure of the sewing surface; then, in order to determine the section, the section generated by the geological structure surface and the modeling range of the boundary surface of the intersection; finally, the use of Delaunay triangular mesh to establish the surface, the boundary section and the bottom of the surface of the TIN model, will be the TIN model collocation! Then, the TIN model can be assembled to build the required 3D geological model.

TIN is a kind of Digital Elevation Model (DEM) method, which has the advantage of reducing the data redundancy brought by the regular grid method, and is better than the pure contour-based method in terms of computational efficiency. Since the complex morphology of geologic bodies cannot be described by regular geometries, there is a need for a more flexible and simpler method to model complex geologic bodies, and TIN is based on this need. This surface model extends the model in computer graphics, which can satisfy the basic requirements of geological mapping, and then carry out the operations of volume estimation, cutting section, surface rendering, 3D display, etc., which is the basis of 3D solid model building.

(3) Wireframe model Boolean operation

This kind of operation is in the establishment of complex geological body mainly on the entity and the entity or entity and the intersection between the surface of the intersection relationship between the intersection of the operation, difference, and so on, to achieve the different entities of the collocation or cutting, so as to get the required entity model. In the modeling practice, the two solid sections are connected to the triangular network according to the straight line, but if the faults are curved surfaces or fault fracture zones, it is difficult to reflect the relationship between the faults and the geologic body, so in order to build a more realistic geologic body can only be realized through the Boolean operation of the wireframe model. Generally in the modeling process, according to the basic Boolean function provided by the 3D software, different Boolean combinations of the entity, that is, you can get the required geological entities.