Abstract

Many of today’s data models for 3D applications, such as City Geography Markup Language (CityGML) or Industry Foundation Classes (IFC) encode rich semantic information in addition to the traditional geometry and materials representation. However, 3D editing techniques fall short of maintaining the semantic information across edit operations if they are not tailored to a specific data model. While semantic information is often lost during edit operations, geometry, UV mappings, and materials are usually maintained. This article presents a data model synchronization method that preserves semantic information across editing operation relying only on geometry, UV mappings, and materials. This enables easy integration of existing and future 3D editing techniques with rich data models. The method links the original data model to the edited geometry using point set registration, recovering the existing information based on spatial and UV search methods, and automatically labels the newly created geometry. An implementation of a Level of Detail 3 (LoD3) building editor for the Virtual Singapore project, based on interactive push-pull and procedural generation of façades, verified the method with 30 common editing tasks. The implementation synchronized changes in the 3D geometry with a CityGML data model and was applied to more than 100 test buildings.

Highlights

  • Many of today’s data models for 3D applications, such as City Geography Markup Language (CityGML) or Industry Foundation Classes (IFC), encode rich semantic information in addition to the traditional geometry and materials representation

  • Hierarchical information carries the relationships between surfaces in 3D models; for instance, in 3D building models, it tells how a window is related to a wall surface

  • We identified five main classes of popular geometry editing techniques: transformation, deletion, deformation, push-pull [6,7], and parametric templates [8,9,10]

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Summary

Introduction

Many of today’s data models for 3D applications, such as CityGML or IFC, encode rich semantic information in addition to the traditional geometry and materials representation. Semantic information provides the identification of key components in a generic 3D model and enables users to differentiate walls, roofs, ground, and other surfaces in a 3D building model. The maintenance of semantic and hierarchical information through the editing process is only supported by specific applications that are closely tied to the underlying data model. In order to provide a flexible integration of existing as well as future editing tools, an automatic matching and synchronization method for the modified geometry and the data model is needed. Many of today’s 3D applications provide SDKs and APIs where 3D geometry, UVs, and materials are exposed, and enable an easy integration of the presented method

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