Three dimensional Boolean operation based on L-Rep model

Abstract

The three dimensional spatial analysis applications of three dimensional GIS in Geology include slice up, palisade map constructing, virtual pit excavation, tunnel simulation etc. At present, these geological spatial analysis applications are implemented by distinct algorithm in different systems. However, those can come down to three dimensional Boolean operation between two spatial entities. Light of the problems of the algorithm complexity, inefficiency, poor stability of numerical calculation existing in the present three dimensional Boolean operation, designed a three dimensional analysis oriented model, L-Rep model, and then researched three dimensional entities Boolean operation algorithm based on this model. The basic idea of L-Rep model is cast Sample Line to three dimensional solid along with coordinate axis direction. Each sample line record the point of it intersected with three dimensional solid. The collection of all sample line composed the L-Rep model. This model not only can express the complex geometric information of entities, such as external borders and internal cracks, but also can express the internal property information of entities completely. Thus, it is able to meet the need of integrating modeling with the geometry and property of the geo-spatial object. Research the Boolean operation method based on L-Rep model of three dimensional entities. By changing the three dimensional spatial analysis into one-dimensional calculation, the speed of the analysis and calculation and the robustness of the algorithm are improved. At last, Taking the surface and underground three dimensional space around the region of University City Xian-lin, Nanjing as the research object, a three dimensional model with complicated geological environment and man-made buildings is established. Based on the new presented three dimensional Boolean operation algorithm, construction the prototype system validates that the method mentioned above is feasible and practicability.