Lod 1 vs. Lod 2 – Preliminary Investigations Into Differences in Mobile Rendering Performance

Abstract

ABSTRACT:The increasing availability, size and detail of 3D City Model datasets has led to a challenge when rendering such data on mobile devices. Understanding the limitations to the usability of such models on these devices is particularly important given the broadening range of applications -such as pollution or noise modelling, tourism, planning, solar potential -for which these datasets and resulting visualisations can be utilized. Much 3D City Model data is created by extrusion of 2D topographic datasets, resulting in what is known as Level of Detail (LoD) 1 buildings -with flat roofs. However, in the UK the National Mapping Agency (the Ordnance Survey, OS) is now releasing test datasets to Level of Detail (LoD) 2 -i.e. including roof structures. These datasets are designed to integrate with the LoD 1 datasets provided by the OS, and provide additional detail in particular on larger buildings and in town centres. The availability of such integrated datasets at two different Levels of Detail permits investigation into the impact of the additional roof structures (and hence the display of a more realistic 3D City Model) on rendering performance on a mobile device. This paper describes preliminary work carried out to investigate this issue, for the test area of the city of Sheffield (in the UK Midlands). The data is stored in a 3D spatial database as triangles and then extracted and served as a web-based data stream which is queried by an App developed on the mobile device (using the Android environment, Java and OpenGL for graphics). Initial tests have been carried out on two dataset sizes, for the city centre and a larger area, rendering the data onto a tablet to compare results. Results of 52 seconds for rendering LoD 1 data, and 72 seconds for LoD 1 mixed with LoD 2 data, show that the impact of LoD 2 is significant.

GeoBIM for built environment condition assessment supporting asset management decision making

“…Although much of the geographic information used within GIS is two-dimensional (2D), increasingly 3D data is now available in many disciplines such as in city planning and disaster response, a 3D representation can increase the insight, improve the visualisation and support the calculation of environmental impacts such as air pollution and noise [28]. Spatial databases allow the complexity in details and the large volume of 3D data to be represented in 3D models [29]. In addition, they provide the opportunity to store multiple levels of detail (granularity, aggregation) from individual features up to portfolio, city and country level.…”

Raise the Roof: Towards Generating Lod2 Models Without Aerial Surveys Using Machine Learning

“…Therefore we have to consider the value of LoD2 over LoD1 from a use case context. At the same time, it should not be neglected that the increase of LoD also increases complexity (Ellul and Altenbuchner, 2013).…”

An improved LOD specification for 3D building models

“…However, their complexity may considerably deviate (Yang et al, 2011), from coarse to fine footprints as seen in Prandi et al (2013) and Ellul and Altenbuchner (2013). This is especially the case in generalisation from finer LODs (Forberg, 2007;Anders, 2005).…”

“…We have encountered several instances of enhanced LOD1 block models with differentiated roof tops (Emem and Batuk, 2004;Commandeur, 2012;Oude Elberink et al, 2013;Döllner et al, 2006;Ellul and Altenbuchner, 2013;He et al, 2013;Häfele, 2011;Sanborn, 2014) that include multiple flat surfaces instead of a single surface for the top, to differentiate terraced houses, large roof constructions, etc. Related to extrusion, sizeable parts of buildings (e.g.…”