Key Technologies of 3D Modeling

The modeling method based on surface model focuses on the surface representation of three-dimensional spatial entities, such as topographic surface, geological level, outline and spatial framework of structures (buildings), underground engineering and so on. The simulated surface may or may not be closed. The grid model based on data interpolation (Figure 5-2) and the TIN model based on sampling points (Figure 5-3) are usually used for non-closed surface simulation. B-rep model and wireframe model are usually used to simulate closed surfaces or external contours.

Figure 5-2 Grid Model

Figure 5-3 tin model

(2) Entity modeling

Three-dimensional solid can be equally divided into countless voxels, and the three-dimensional voxel filling model divides three-dimensional space objects into groups of adjacent but non-overlapping three-dimensional voxels. It uses a voxel containing points to represent a point object, a group of adjacent voxels extending in one direction (the direction can be changed at will) to represent a linear object, and a group of adjacent voxels extending in two directions to represent a planar object. Volume model is based on voxel segmentation and true three-dimensional entity expression in three-dimensional space, and the attributes of voxels can be described and stored independently, so it can be operated and analyzed in three-dimensional space. According to the regularity of voxels, they can be divided into regular voxels and irregular voxels. Regular voxels include CSG tree, voxel model, octree model (Figure 5-4), Needle model and RegularBlock)***5 * 5 model.

Figure 5-4 Octree Model