基于GTP修正的R3DGM建模与可视化方法

Modeling and visualizing methods for real 3D geosciences model based on amended generalized tri-prism(GTP)

将广义三棱柱(GTP)的辅助几何要素———对角线———修正为四面体,解决了R3DGM(真三维地学模型)中数据组织与几何要素的不一致和空间操作中的几何裂缝问题.修正后的GTP模型集成了TIN,GTP和四面体模型的优点,构建算法简单且空间操作无缝.R3DGM过程分3步进行:①根据钻孔孔口数据点与断层露头约束,按约束Delaunay法则生成地表不规则三角网(CD-TIN);②按地学推理规则,将CD-TIN中三角形沿钻孔迹线向下扩展生成GTP;③根据最小顶点标识法,将GTP模型转换成四面体.介绍了基于GTP修正构建的三维数字地质模型的任意平面剖切、虚拟开挖、空间查询等可视化方法.并结合北京CBD地下三维集成建模与空间操作,展示了模型构模及空间操作效果.

By amending the auxiliary geometric primitive, diagonal, of generalized tri-prism （GTP） into tetrahedron, the inconsistentness of data organization and of geometric primitive in real 3 D geosciences modeling as well as the geometric interstice in spatial operation were solved. The amended GTP model synthesized the merits of TIN, GTP and tetrahedron, and its constructing algorithm was simple and the spatial operation on it is seamless. The modeling process for R3 DGM includes： ① to generate the constrained delaunay TIN （CD-TIN） of terrain according to the collar data of borehole and the outcrops of faults ; ② to extend each triangle of the CD-TIN downward to generate a GTP along the borehole tracks referring to the geo-inference rules; and ③ to convert the GTP model into tetrahedron model based on the smallest vertex identifier （SVID） method. The visualizing methods for arbitrary planar cutting, virtual excavation designing, virtual wandering and spatial inquiry on so constructed R3DGM were illustrated, and the effects out from the methods are shown with the real 3 D integral modeling and 3 D spatial operations for the underground geo-technical environment of CBD in Beijing being an example.