Abstract
With the increasing needs of and rapid developments in digital and/or smart cities, an effective method for the management of various types of complex and massive buildings for the creation of a three-dimensional (3D) photorealistic city has become crucial for high-quality “digital/smart city” construction. To this end, this paper proposes a data model called the “SCSG-OSM”, which combines spatial constructive solid geometry (SCSG) and the object-based spatial model (OSM). The SCSG-OSM assumes an object can be represented by four element types: point, line, face and body. The SCSG applies an extension of the dimensionally extended nine-intersection model (DE-9IM) to describe the spatial topological relationship. The OSM consists of nine definitions that define the points, lines, faces, and bodies of an object and applies point sets instead of node sets and face sets instead of surface sets to model buildings. Two data sets, depicting Denver, Colorado, USA, and Zurich, Switzerland, are employed to assess the storage space and the time consumption averages during the modelling of 3D buildings using the proposed data model. The experimental results demonstrate that the proposed SCSG-OSM is able to save storage space and reduce the computational time compared with the CSG-BR model, TIN model, POLYGON model, Patch model, SSM and CityGML model. Therefore, it can be concluded that the method proposed in this paper is a simple and effective method for the 3D photorealistic visualization of a large city.
Highlights
With the rapid developments and increasing needs of the construction of ‘‘smart/digital cities’’, high-quality three-dimensional (3D) models of buildings for photorealistic visualization are in great demand
The simple spatial model (SSM) is effective for the spatial visualization and query of 3D buildings, but the conversion of points, lines, surfaces and bodies into nodes and faces in the SSM is time consuming
This paper proposes an spatial constructive solid geometry (SCSG)-object-based spatial model (OSM) method based on the SSM
Summary
With the rapid developments and increasing needs of the construction of ‘‘smart/digital cities’’, high-quality three-dimensional (3D) models of buildings for photorealistic visualization are in great demand. Fp=1 c) If the intersection of each pair of points, denoted by Pfp1 ∈ Fx1 and Pfp2 ∈ Fx2, is an empty set, the two faces Fx1 and Fx2 are disjoint Py} ⊂ Fi, the interior of the face Fj does not contain the set of lines Li. 4) PRINCIPLES OF BODY a: DEFINITIONS OF BODY (SUCH AS A BUILDING) A body is mathematically defined as k. Bf =1 where Bb is an indexed set (such as several buildings) containing k faces of Fi, 4 ≤ k ≤ fpn, 1 ≤ i ≤ k, fpn is the total number of faces, bf is the unique body index of a face, and Fi is the faces of Bb. The characteristics are as follows: a) The points of a body can be expressed by k1 k2. Nib=1 where nib is the point-in-body index of the point
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