Abstract
A 3D city model is an intuitive tool that is used to describe cities. Currently, level-of-detail (LOD) technology is used to meet different visual demands for 3D city models by weighting the rendering efficiency against the details of the model. However, when the visual demands change, the “popping” phenomenon appears when making transformations between different LOD models. We optimized this popping phenomenon by improving the data structure that focuses on 3D city building models and combined it with the facet shift algorithm based on minimal features. Unlike generating finite LOD models in advance, the proposed continuous LOD topology data structure is able to store the changes between different LOD models. By reasonably using the change information, continuous LOD transformation becomes possible. The experimental results showed that the continuous LOD transformation based on the proposed data structure worked well, and the improved data structure also performed well in memory occupation.
Highlights
With the rise of data science, the urban informatization wave has had an enormous impact on various trades and occupations, and the "Smart City" has globally become a new theory and practice for next-generation urban development [1]
The rational use of 3D city models will help elevate the level of city planning and provide references for actual construction processes, which plays an important role in the rational allocation of construction costs and resources. 3D city models are considered to be the application foundation of urban planning thematic information visualization [5,6,7,8,9], which has become a research hot spot in the Smart City field
The main method of continuous transformation of 3D building models is "fading", which is based on discrete LOD technology
Summary
With the rise of data science, the urban informatization wave has had an enormous impact on various trades and occupations, and the "Smart City" has globally become a new theory and practice for next-generation urban development [1]. The discrete LOD technique pregenerates and stores several models in different levels of detail It omits the processing time of real-time simplified models; it occupies more storage space and mutates the visual effects while switching from one level of detail to another. The main method of continuous transformation of 3D building models is "fading", which is based on discrete LOD technology. It makes use of the transparent rendering effect of graphics hardware and realizes the transition of models at different levels of detail by setting transparent attributes of certain objects at different stages. TThhee rrooooff ssttyylleess ooff uurrbbaann bbuuiillddiinnggss ccaann bbee rroouugghhllyy ddiivviiddeedd iinnttoo tthhrreeee ccaatteeggoorriieess((FFiigguurree 22)):: ffllaatt,, ssppiirree,, aanndd ssllooppeedd rrooooffss. Geo-Inf. 2019, 8, x FOR PEER REVIEW ISPRS Int. J.
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