Abstract:There is an increasing need for building models that permit interior navigation, e.g., for escape route analysis. This paper presents a non-manifold Computer-Aided Design (CAD) data structure, the dual half-edge based on the Poincaré duality that expresses both the geometric representations of individual rooms and their topological relationships. Volumes and faces are expressed as vertices and edges respectively in the dual space, permitting a model just based on the storage of primal and dual vertices and edges. Attributes may be attached to all of these entities permitting, for example, shortest path queries between specified rooms, or to the exterior. Storage costs are shown to be comparable to other non-manifold models, and construction with local Euler-type operators is demonstrated with two large university buildings. This is intended to enhance current developments in 3D Geographic Information Systems for interior and exterior city modelling.Keywords: three-dimensional modelling; solid modelling; data structures; Euler operators
GIS HistoryThis paper presents a detailed technical description and properties of the dual half-edge (DHE) topological data structure and its application in the Geographic Information Sciences (GIS), particularly in building interior modelling. It includes associated navigation and construction operators necessary for a convenient usage of DHE. Previous papers describing DHE [1][2][3] reported on the importance of the primal/dual approach, some applications, model representation and preliminary development, but with only a brief discussion of technical details and properties. DHE is compared with some other similar data structures.Early 2D GIS data structures were designed for polygon (choropleth) maps, where the objective was to combine the sets of individual digitized polygon boundaries to form a network. Various approaches were attempted, but finally an arc-based structure predominated, where an "arc" consisted of an intermediate set of digitized points between the "nodes" at boundary junctions. This was closely related to the winged-edge structure [4], with pointers to the four adjacent arcs and the two bounding polygons. The winged-edge structure was developed by Baumgart [4] and provided a way to connect