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The global building sector plays a pivotal role in addressing sustainability, climate change, and carbon neutrality. This study introduces the original concept of virtual building models (VBMs) throughout the lifecycle of the building industry, considering the unique characteristics of this industry. VBMs are defined as mathematical models that represent the physical behavior of buildings throughout their lifecycle. These models consist of subvirtual models that represent the physical operational environments of the target building, encompassing physical variables, equipment, systems, indoor environments, and structural and material behaviors. This concept can contribute to achieving the existing concepts of building information modeling, digital twins, and cyber-physical systems within building operations, communities, and environments. In this study, building models are categorized into five aspects: virtual model environments, types, interactions, integrations, and levels of detail (LODs). The LODs are classified into five levels (LOD100, LOD200, LOD300, LOD350, and LOD400) depending on the primary environments of the virtual models and their coverage across the entire building. Virtual modeling methodologies are proposed considering the virtual model aspects to achieve higher or intended LOD states from both academic and industrial perspectives. Finally, future research directions are discussed to drive the concept of virtual buildings to shape the future of the building industry through digital transformations.

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Urban planning and urban design involve complex processes that require detailed information about the visual information of a place at various scales. Different graphic tools, such as game engines, are evolving to use urban representation fields. The concept of "level of detail" (LOD) has been used to categorize the level of detail in AEC applications such as BIM and GML for urban representation models. However, there is a need to distinguish between different LOD concepts commonly used in various fields, as these terms have different interpretations and implications. This article presents a novel approach to re-categorizing the level of detail concept in AEC applications, led by the traditional use of LOD and in parallel with urban planning scales. From an urbanist perspective, a four-stage LOD classification framework has been studied: LOD 1000 for urban and neighbourhood scales, LOD 2000 for the plaza and square scales, LOD 3000 for architectural and street scales, and LOD 4000 for protected and private areas. [ABSTRACT FROM AUTHOR]

The Level of Detail (LoD), a parameter used to define the information contained in building models, is an important factor to consider in modeling building energy at the urban scale. In this research, we conducted a parametric study regarding the data requirements for the estimation of the annual residential heat demand in London. More particularly, the requirement of the observation of the actual roof type (LoD2) and the window-to-wall ratio (LoD3) was examined in two different case study areas. Meanwhile, an adaptive comfort level study was implemented using LoD5 models, and its results were assessed holistically with the heat demand to reveal the energy performance of the buildings. The results showed that there was a minor difference in the upgrade of a lower to higher LoD regarding these parameters. At an urban scale, the energy demand of buildings could be estimated using an assumption of archetypes and building ages. However, with a scalable parametric script developed in places, models with a high LoD could provide more detailed insights in the energy performance assessment without generating excessive workload. [ABSTRACT FROM AUTHOR]

This study summarises research progress to identify appropriate quality methodologies for representing, interpreting, and modelling complex contexts such as the Claudian Aqueduct in the Appian Way Archaeological Park. The goal is to intrinsically integrate (embed) geometric survey (Laser scanning and photogrammetric) with the materials and construction techniques (Stratigraphic Units—SU), semantic models in order to support the design with a better understanding of the artefact considered, and also to give indications that can be implemented in the future in a continuous cognitive process. Volume stratigraphic units in the form of architectural drawings, heritage building information modelling (HBIM) and extended reality (XR) environments have been oriented to comparative analyses based on the research case study's complex morphology. Analysis of geometries' intersection, construction techniques and materials open up new cognitive scenarios, self-feeding a progressive knowledge and making different studies correlatable, avoiding diaspora or incommunicability. Finally, an extended reality (XR) platform aims to enhance tangible and intangible values through new human-computer interaction and information sharing levels. [ABSTRACT FROM AUTHOR]

The accuracy of daylighting simulations for the built environment strongly depends on the modeling of the exterior surround. The practice of modeling a space with a flat ground surface with little or no external architectural or landscape elements, particularly early in the design phase, is often applied. In this study, this approach and a number of different levels of detail for modeling the exterior surround were investigated by comparing real-life empirical measurements with their corresponding simulation results. A total of 13 different exterior views were studied under 15 different sky/seasonal conditions to investigate the contribution of the surrounding features to the daylight delivered inside a small office. These features were classified into one of four different groups – sky, architectural structures, standing vegetation, and horizontal ground. Five of these locations were chosen for further simulation by applying six levels of detail to the exterior surround in a simulation model. The results reveal that ignoring exterior surround objects (common practice for some) yielded an average error of 67.9%, while a high level of detail (which applied high polygon vegetation representations) resulted in an average error of only 11.3%. A detailed model of the surround with the IES LM-83 suggested method of modeling trees resulted in an average error of 22.8%. [ABSTRACT FROM AUTHOR]

Human factors studies are becoming more and more crucial in the automotive sector due to the need to evaluate the driver.s reactions to the increasingly sophisticated driving-assistant technologies. Driving simulators allow performing this kind of study in a controlled and safe environment. However, the driving simulation.s Level of Detail (LOD) can affect the users. perception of driving scenarios and make an experimental campaign.s outcomes unreliable. This paper proposes a study investigating possible correlations between driver.s behaviors and emotions, and simulated driving scenarios. Four scenarios replicating the same real area were built with four LODs from LOD0 (only the road is drawn) to LOD3 (all buildings with real textures for facades and roofs are inserted together with items visible from the road). 32 participants drove in all the four scenarios on a fixed-base driving simulator; their performance relating to the vehicle control (i.e., speed, trajectory, brake and gas pedal use, and steering wheel), their physiological data (electrodermal activity, and eye movements), their subjective perceptions, opinions and emotional state were measured. The results showed that drivers. behavior changes in a very complex way. Geometrical features of the route and environmental elements constrain much more driving behavior than LOD does Emotions are not affected by LODs. Generally, different signals showed different correlations with the LOD level, suggesting that future studies should consider their measures while modeling the virtual scenario. It is hypothesized that scenario realism is more relevant during leisurely environmental interaction, whilst simulator fidelity is crucial in task-driven interactions. [ABSTRACT FROM AUTHOR]

In this work, we propose a novel solution for simplifying texture-mapped three-dimensional (3D) meshes. It simplifies a 3D triangular mesh to optimally preserve the visual appearance of the original texture-mapped model at reduced vertex budgets. While taking the prevalent strategy of iterative edge contraction, the proposed scheme is novel in that it takes into account the local texture image characteristics when prioritizing local mesh simplification operators, and conducts closed-form optimization when computing the texture coordinates of each replacement vertex. Outstanding performance of the proposed scheme is demonstrated both qualitatively and quantitatively by experimental results. Further, validity of the proposed algorithmic components is well proved through ablation study.

• An error-bounded screen space terrain rendering approach. • Better terrain shading details with self-occlusion and normal filtering. • A new multi-resolution terrain rendering algorithm that utilizes summed-area tables (SATs). [Display omitted] Due to the fundamental weaknesses of level-of-detail (LOD) control and rich details in the Geometry Clipmaps, we propose a multi-resolution terrain rendering algorithm that utilizes summed-area tables (SATs) [1] to facilitate the rendering of terrain with better geometric and shading details. First, our algorithm introduces a novel geometric error bound on the screen-based terrain rendering approach that juggles low rendering throughput and better LOD control. Geometric errors are estimated in real-time from SATs, enabling error-bounded geometry clipmap. Second, we utilize Spherical Gaussian (SG) functions to approximate lighting and bidirectional reflection distribution functions (BRDFs), and efficiently calculate outgoing radiance with self-occlusions of the terrain. SATs are utilized to enable the mipmapping of visibility and normal maps. We demonstrate the improvements of our method with experiments on accuracy and efficiency. [ABSTRACT FROM AUTHOR]

Integrating a BIM-based life-cycle assessment (LCA) in the early design stages of building projects can promote a reduction of environmental impacts. However, the reliability of the analysis depends on the quality of the model. BIM modelling of timber-frame construction is often simplified, potentially hindering the LCA outcome due to quantity inaccuracy and a failure to consider elements regarded as negligible. This study addresses the methodological problem that influences the calculation of the environmental impact by examining the various environmental impacts caused by inventory data obtained from BIM models with a level of detail of (LOD)350–400 vs LOD200. The environmental impacts obtained from both models of a timber building calculated through an attributional LCA method are compared. Material inventory sourced from the LOD200 model results in a 14.7% lower value of embodied impact. The discrepancies resulted from aluminium, mineral wool and bitumen, which are identified as critical materials requiring quantity adjustment. Relying on simplified BIM models for LCA may lead to the GWP being under-estimated with incorrect identification of hotspots in the early design stages. The results aksi question the cut-off criterion of the current EN15978 norm that serves as a foundation for developing environmental policies within the industry. It recommends exclusion of materials constituting less than 1% of the overall mass from the system boundary. This study underscores the potential significance of materials falling below this threshold, challenging the validity of the criterion, and suggesting that such materials should be carefully evaluated and included in the LCA to ensure a comprehensive assessment of the environmental impacts. The overall objective of the study is to emphasize the importance of employing accurate BIM models in LCAs to make informed decisions that are aligned with the sustainability goals, encouraging practitioners to consider the impact of critical materials, even those with seemingly minimal contributions. With this knowledge, the practitioners are able to take meaningful actions that compensate for the LCA uncertainty, mitigating the environmental burden of the most impactful areas. Most importantly, the findings aim to identify the error in design LCA versus as-built studies, helping to develop design LCA tools that predict the as-built impact more precisely and earlier in the design process. The findings can also improve the expected building model definition in carbon policies. • Compare GWP score of building calculated with LOD200 and LOD400. • A difference of 14.7% of embodied impact between results. • Simplified BIM models may underestimate the GWP and incorrectly identify hotspots. • Discrepancies resulted from aluminium, mineral wool and bitumen being identified as critical materials. [ABSTRACT FROM AUTHOR]

Persistent scatterers (PSs) are coherent measurement points obtained from time series of satellite radar images, which are used to detect and estimate millimeter-scale displacements of the terrain or man-made structures. However, associating these measurement points with specific physical objects is not straightforward, which hampers the exploitation of the full potential of the data. We have investigated the potential for predicting the occurrence and location of PSs using generic 3-D city models and ray-tracing methods, and proposed a methodology to match PSs to the pointlike scatterers predicted using RaySAR, a ray-tracing synthetic aperture radar simulator. We also investigate the impact of the level of detail (LOD) of the city models. For our test area in Rotterdam, we find that 10% and 37% of the PSs detected in a stack of TerraSAR-X data can be matched with point scatterers identified by ray tracing using LOD1 and LOD2 models, respectively. In the LOD1 case, most matched scatterers are at street level while LOD2 allows the identification of many scatterers on the buildings. Over half of the identified scatterers easily correspond to identify double or triple-bounce scatterers. However, a significant fraction corresponds to higher bounce levels, with approximately 25% being fivefold-bounce scatterers. [ABSTRACT FROM AUTHOR]

Due to rapid technological development, virtual reality (VR) is becoming an accessible and important tool for many applications in science, industry, and economy. Being immersed in a 3D environment offers numerous advantages especially for the presentation of geographical data that is usually depicted in 2D maps or pseudo 3D models on the monitor screen. This study investigated advantages, limitations, and possible applications for immersive and intuitive 3D terrain visualizations in VR. Additionally, in view of ever-increasing data volumes, this study developed a workflow to present large scale terrain datasets in VR for current mid-end computers. The developed immersive VR application depicts the Arctic fjord Clyde Inlet in its 160 km x 80 km dimensions at 5 m spatial resolution. Techniques, such as level of detail algorithms, tiling, and level streaming, were applied to run the more than one gigabyte large dataset at an acceptable frame rate. The immersive VR application offered the possibility to explore the terrain with or without water surface by various modes of locomotion. Terrain textures could also be altered and measurements conducted to receive necessary information for further terrain analysis. The potential of VR was assessed in a user survey of persons from six different professions. [ABSTRACT FROM AUTHOR]

Abstract The interior of a building may be more complicated than its exterior because such an indoor space comprises a number of three-dimensional (3D) non-overlapping regions called cells (e.g. rooms). Owing to the complexity of 3D geometry, applications with 3D data (e.g. indoor navigation) require an adequate level of detail (LoD) to achieve their purpose. To supply the 3D data demanded by clients, a customised simplification that considers LoDs in an indoor space is required. Most research studies on the simplification of 3D objects, however, have focused on general 3D objects or the exterior of buildings. Applying such approaches to indoor space objects is inefficient and may cause loss of important information because cells in an indoor space have distinctive characteristics compared to general 3D objects. For instance, a conventional room is surrounded by vertically aligned walls and a horizontally aligned ceiling and floor. For this reason, we propose a dedicated simplification method of 3D geometric objects in an indoor space. Our method takes full advantage of the prism model, which is an alternative 3D geometric model that supports prismatic shapes motivated by traits of indoor spaces. Additionally, an approach for dealing with potential topological inconsistencies during simplification is presented in this paper. An empirical analysis of the efficiency of the proposed simplification is conducted to validate our work. [ABSTRACT FROM AUTHOR]

The increasing application of BIM processes and technologies has facilitated an increase in the use of 4D (3D+Time) simulations of construction projects. Previous research has acknowledged the benefit of 4D models in the project planning and construction phases enhancing communication between construction teams and avoiding unforeseen conflicts during the build process. The development of BIM has spurred a deeper understanding of the issues surrounding Level of Development, Level of Information (LOI) and Level of Detail (LOD) pertaining to the graphical detail and non-graphical information of the static geometric design model. However, to date there is limited research thoroughly investigating the issue of LOD within 4D applications. This work presents an ongoing study to derive a framework for the development of more dynamic 4D simulations incorporating discrete forms of LOD. Level of graphical detail (LODg) corresponds to the graphical detail of the model geometry and also the 'granularity' of the geometry required for dynamic 4D production, whilst the temporal level of detail (LODti) relates to time period required between state changes in the model during the simulation. In order to support the development of the framework, an industry-based survey was conducted to assess the application of 4D, subsequent issues and use cases around levels of graphical and temporal details to improve dynamic 4D simulations. The work concludes with the development of a framework and schematic to support the specification of the LOD of a 4D simulation (LOD4d) throughout the various phases of a construction project. [ABSTRACT FROM AUTHOR]

The various levels of detail (LODs) of a 3D city model are often stored independently, without links between the representations of the same object, causing inconsistencies, as well as update and maintenance problems. One solution to this problem is to model the LOD as an extra geometric dimension perpendicular to the three spatial ones, resulting in a true 4D model in which a single 4D object (a polychoron) represents a 3D polyhedral object (e.g., a building) at all of its LODs and a multiple-LOD 3D city model is modeled as a 4D cell complex. While such an approach has been discussed before at a conceptual level, our objective in this paper is to describe how it can be realized by appropriately linking existing 3D models of the same object at different LODs. We first present our general methodology to construct such a 4D model, which consists of three steps: (1) finding corresponding 0D–3D cells; (2) creating 1D–4D cells connecting them; and (3) constructing the 4D model. Because of the complex relationships between the objects in different LODs, the creation of the connecting cells can become difficult. We therefore describe four different alternatives to do this, and we discuss the advantages and disadvantages of each in terms of their feasibility in practice and the properties that the resulting 4D model has. We show how the different linking schemes result in objects with different characteristics in several use cases. We also show how our linking method works in practice by implementing the linking of matching cells to construct a 4D model.

Nowadays, spatial information plays a fundamental role in many processes related to with spatial planning. More and more complicated, complex decisions must be taken effectively in a very short time. In recent years, and certainly since 2007, when the Directive Spatial Information Infrastructure in the European Community 2007/2 / EC of the European Parliament of the European Union entered into force, 3D modelling has become a rapidly growing branch of the Geographic Information System supporting the making of important decisions. 3D modelling conceals many working techniques, eg. automatic generation of 3D models based on a set of geometric rules using spatial data with the adopted level of LOD detail. ESRI CityEngine is one of the programs enabling such work thanks to the implementation of the computer-generated engineering grammar (CGA) that extracts threedimensional objects from 2D data. In this work, procedural modelling tools were used on spatial data acquired for the Polish district in the city of Detroit, in the United States, in Michigan. The main goal was not to accurately reflect the real appearance of the settlements, what to recognize the process and opportunities offered by CGA grammar, obtain models at the LOD2 level (building block with the shape of the roof) and use them to analyse the visibility in the sample situation. [ABSTRACT FROM AUTHOR]

Due to rapid technological development, virtual reality (VR) is becoming an accessible and important tool for many applications in science, industry, and economy. Being immersed in a 3D environment offers numerous advantages especially for the presentation of geographical data that is usually depicted in 2D maps or pseudo 3D models on the monitor screen. This study investigated advantages, limitations, and possible applications for immersive and intuitive 3D terrain visualizations in VR. Additionally, in view of ever-increasing data volumes, this study developed a workflow to present large scale terrain datasets in VR for current mid-end computers. The developed immersive VR application depicts the Arctic fjord Clyde Inlet in its 160 km × 80 km dimensions at 5 m spatial resolution. Techniques, such as level of detail algorithms, tiling, and level streaming, were applied to run the more than one gigabyte large dataset at an acceptable frame rate. The immersive VR application offered the possibility to explore the terrain with or without water surface by various modes of locomotion. Terrain textures could also be altered and measurements conducted to receive necessary information for further terrain analysis. The potential of VR was assessed in a user survey of persons from six different professions.

The production and dissemination of semantic 3D city models is rapidly increasing benefiting a growing number of use cases. However, their availability in multiple LODs and in the CityGML format is still problematic in practice. This hinders applications and experiments where multi-LOD datasets are required as input, for instance, to determine the performance of different LODs in a spatial analysis. An alternative approach to obtain 3D city models is to generate them with procedural modelling, which is--as we discuss in this paper--well suited as a method to source multi-LOD datasets useful for a number of applications. However, procedural modelling has not yet been employed for this purpose. Therefore, we have developed RANDOM3DCITY, an experimental procedural modelling engine for generating synthetic datasets of buildings and other urban features. The engine is designed to produce models in CityGML and does so in multiple LODs. Besides the generation of multiple geometric LODs, we implement the realisation of multiple levels of spatiosemantic coherence, geometric reference variants, and indoor representations. As a result of their permutations, each building can be generated in 392 different CityGML representations, an unprecedented number of modelling variants of the same feature. The datasets produced by RANDOM3DCITY are suited for several applications, as we show in this paper with documented uses. The developed engine is available under an open-source licence at Github at http://github.com/tudelft3d/Random3Dcity. [ABSTRACT FROM AUTHOR]

In construction environments, laser-scanning technologies can perform rapid spatial data collection to monitor construction progress, control construction quality, and support decisions about how to streamline field activities. However, even experienced surveyors cannot guarantee comprehensive laser scanning data collection in the field due to its constantly changing environment, wherein a large number of objects are subject to different data-quality requirements. The current practice of manually planned laser scanning often produces data of insufficient coverage, accuracy, and details. While redundant data collection can improve data quality, this process can also be inefficient and time-consuming. There are many studies on automatic sensor planning methods for guided laser-scanning data collection in the literature. However, fewer studies exist on how to handle exponentially large search space of laser scan plans that consider data quality requirements, such as accuracy and levels of details (LOD). This paper presents a rapid laser scan planning method that overcomes the computational complexity of planning laser scans based on diverse data quality requirements in the field. The goal is to minimize data collection time, while ensuring that the data quality requirements of all objects are satisfied. An analytical sensor model of laser scanning is constructed to create a “divide-and-conquer” strategy for rapid laser scan planning of dynamic environments wherein a graph is generated having specific data quality requirements (e.g., levels of accuracy and detail of certain objects) in terms of nodes and spatial relationships between these requirements as edges (e.g., distance, line-of-sight). A graph-coloring algorithm then decomposes the graph into sub-graphs and identifies “local” optimal laser scan plans of these sub-graphs. A solution aggregation algorithm then combines the local optimal plans to generate a plan for the entire site. Runtime analysis shows that the computation time of the proposed method does not increase exponentially with site size. Validation results of multiple case studies show that the proposed laser scan planning method can produce laser-scanning data with higher quality than data collected by experienced professionals, and without increasing the data collection time. [ABSTRACT FROM AUTHOR]

3D city models of the same region at multiple LODs are encumbered by the lack of links between corresponding objects across LODs. In practice, this causes inconsistency during updates and maintenance problems. A radical solution to this problem is to model the LOD of a model as a dimension in the geometric sense, such that a set of connected polyhedra at a series of LODs is modelled as a single polychoron--the 4D analogue of a polyhedron. This approach is generally used only conceptually and then discarded at the implementation stage, losing many of its potential advantages in the process. This paper therefore shows that this approach can be instead directly realised using 4D combinatorial maps, making it possible to store all topological relationships between objects. [ABSTRACT FROM AUTHOR]

The various levels of detail (LODs) of a 3D city model are often stored independently, without links between the representations of the same object, causing inconsistencies, as well as update and maintenance problems. One solution to this problem is to model the LOD as an extra geometric dimension perpendicular to the three spatial ones, resulting in a true 4D model in which a single 4D object (a polychoron) represents a 3D polyhedral object (e.g., a building) at all of its LODs and a multiple-LOD 3D city model is modeled as a 4D cell complex. While such an approach has been discussed before at a conceptual level, our objective in this paper is to describe how it can be realized by appropriately linking existing 3D models of the same object at different LODs. We first present our general methodology to construct such a 4D model, which consists of three steps: (1) finding corresponding 0D-3D cells; (2) creating 1D-4D cells connecting them; and (3) constructing the 4D model. Because of the complex relationships between the objects in different LODs, the creation of the connecting cells can become difficult. We therefore describe four different alternatives to do this, and we discuss the advantages and disadvantages of each in terms of their feasibility in practice and the properties that the resulting 4D model has. We show how the different linking schemes result in objects with different characteristics in several use cases. We also show how our linking method works in practice by implementing the linking of matching cells to construct a 4D model. [ABSTRACT FROM AUTHOR]

Recently, the built heritage sector has witnessed an increase demand for 3D models of historical sites mainly due to the widespread of new technologies in buildings' surveying. Although these technologies have been credited for enabling highly detailed 3D modelling of the built heritage, their implementation is still so complex and costly. This research aims to explore the possibility of implementing new low-cost digital acquisition technologies and modelling techniques as an alternative to the existing expensive ones in terms of level of detail (LOD), as an attempt to enable lowskilled users in simplified environment, which are faced paced leaning milieus in education, places with high constraints, or developing countries, to practically learn about their built heritage; consequently, contribute to its preservation. To achieve this purpose, the most diffused SFM and laser scanning open-source packages were first cross-compared using web-content analysis data collection method. Afterwards, the best programme from each category namely; Autodesk 123D catch and Reconstructme, accompanied with Canon D550 camera and Xbox Kinect, respectively, were intensively evaluated through an experiment. The analysis of the findings has suggested that low-cost close-range photogrammetry can replace laser scanning when there is a lack of funding and time. [ABSTRACT FROM AUTHOR]

Virtual reality (VR) transports the mind beyond the two-dimensional bounds of text and photographs; it engages the imagination and forms visual and cognitive links. VR can free participants from stereotyped bounds projected by society. Interconnections: Revisiting the Future applies these innate qualities of virtual worlds to weave together individual threads of singular disciplines into a multidisciplinary tapestry of exploration. The authors are creating an accurately modeled 1964–1965 New York World’s Fair where users can freely explore 140+ pavilions set on 660 virtual square acres. The myriad of pavilions offer links to multiple disciplines—science, engineering, technology, national and international political/cultural affairs, art, history, and architecture. The project provides on-site museum experiences with its partners, the New York Hall of Science and Queens Museum of Art. The three-dimensional virtual Fair environment serves as a central portal that links together not only subjects within that environment but also experiences at these partnering institutions. [ABSTRACT FROM PUBLISHER]

Abstract: Geoscientists build dynamic models to simulate various natural phenomena for a better understanding of our planet. Interactive visualizations of these geoscience models and their outputs through virtual globes on the Internet can help the public understand the dynamic phenomena related to the Earth more intuitively. However, challenges arise when the volume of four-dimensional data (4D), 3D in space plus time, is huge for rendering. Datasets loaded from geographically distributed data servers require synchronization between ingesting and rendering data. Also the visualization capability of display clients varies significantly in such an online visualization environment; some may not have high-end graphic cards. To enhance the efficiency of visualizing dynamic volumetric data in virtual globes, this paper proposes a systematic framework, in which an octree-based multiresolution data structure is implemented to organize time series 3D geospatial data to be used in virtual globe environments. This framework includes a view-dependent continuous level of detail (LOD) strategy formulated as a synchronized part of the virtual globe rendering process. Through the octree-based data retrieval process, the LOD strategy enables the rendering of the 4D simulation at a consistent and acceptable frame rate. To demonstrate the capabilities of this framework, data of a simulated dust storm event are rendered in World Wind, an open source virtual globe. The rendering performances with and without the octree-based LOD strategy are compared. The experimental results show that using the proposed data structure and processing strategy significantly enhances the visualization performance when rendering dynamic geospatial phenomena in virtual globes. [Copyright &y& Elsevier]

[Display omitted] • Extension to openBIM data model IFC to promote BIM use in underground station. • Proposal of geotechnical analysis MVD via key activities identification. • Development of a multi-LOD BIM parametric station model. • Proposal of a design-to-design workflow between BIM authoring and numerical modelling. • Demonstration of design efficiency and integrated visualisation via a prototype. Underground metro stations as essential large-scale infrastructures that ease the traffic congestion on the overcrowded urban surface should be thoroughly designed, constructed and maintained. Building information modelling (BIM) has been increasingly employed for project design authoring, construction monitoring and operation management to promote digital engineering. Geotechnical design engaging numerical modelling techniques is an indispensable process for underground construction projects. These cross-disciplinary processes employing heterogeneous applications are yet to be coordinated in an efficient way, and thus improved interoperability can streamline the processes and optimise engineering design. This paper proposes an extension to the primary standard for openBIM data exchange – the Industry Foundation Classes (IFC) to facilitate wider adoption of BIM in underground infrastructure design, construction and management. Then a multiple level-of-detail (LOD) metro station BIM model is introduced to represent information at distinct levels of geometric and semantic richness required for varying application scenarios. Finally, we suggest a workflow underpinned by heuristic techniques, as an intermediate solution, to enhance the interoperability between a BIM authoring tool and a numerical modelling program for geotechnical analysis, and exemplify the workflow with the State Library Station of Melbourne. The proposed workflow offers an automated error-free, design-to-design solution, and hence enables the efficient exploration of design scenarios and construction optimisation before IFC is adopted by geotechnical modelling software. [ABSTRACT FROM AUTHOR]

3D computer-aided design (CAD) systems based on feature-based solid modelling technique have been widely spread and used for product design. However, when part models associated with features are used in various downstream applications, simplified models in various levels of detail (LODs) are frequently more desirable than the full details of the parts. In particular, the need for feature-based multiresolution representation of a solid model representing an object at multiple LODs in the feature unit is increasing for engineering tasks. One challenge is to generate valid models at various LODs after an arbitrary rearrangement of features using a certain LOD criterion, because composite Boolean operations consisting of union and subtraction are not commutative. The other challenges are to devise proper topological framework for multiresolution representation, to suggest more reasonable LOD criteria, and to extend applications. This paper surveys the recent research on these issues. [ABSTRACT FROM AUTHOR]

Efficient online visualization of three-dimensional (3-D) textured models is essential for a variety of applications including not only games and e-commerce, but also heritage and medicine. To visualize 3-D objects online, it is necessary to quickly adapt both mesh and texture to the available computational or network resources. Earlier research showed that after reaching a minimum required mesh density, high-resolution texture has more impact on human perception than a denser mesh. Given limited bandwidth, an important issue is how to extract features that best represent the original object, and how to allocate resources between mesh and texture data to achieve optimal perceptual quality. In this paper, we propose a textured mesh (TexMesh) model, which applies scale-space analysis and perceptual evaluation to extract 3-D features for textured mesh simplification and transmission. Texture data is divided into fragments to facilitate quality and bandwidth adaptation. Texture quality assignment is based on feature point distribution. Online transmission is based on statistics gathered during preprocessing, which are stored in a priority queue and lookup tables. Quality of service requested by a client site can be met by applying an efficient adaptive algorithm to ensure optimal use of the specified time and available bandwidth, and at the same time preserving satisfactory quality. Our TexMesh framework integrates feature extraction, mesh simplification, texture reduction, bandwidth adaptation, and perceptual evaluation into a multiscale visualization framework. [ABSTRACT FROM AUTHOR]

Terrestrial Laser Scanning (TLS) is an efficient and reliable method for collecting point clouds which have a range of applications in the Architecture, Engineering and Construction (AEC) domain. To ensure that the acquired point clouds are suitable to any given application, data collection must guarantee that all scanning targets are acquired with the specified data quality, and within time limits. Efficiency of data collection is important to reduce jobsite activity disruptions. Effective and efficient laser scanning data collection can be achieved through a prior planning optimisation process, which can be called Planning for Scanning (P4S). In the construction domain, the P4S problem has attracted increasing interest from the research community and a number of approaches have been proposed. This manuscript presents a systematic review of prior P4S works in the AEC domain and presents a categorisation of point cloud data quality criteria. The review starts with the identification and grouping in three categories of the point cloud data quality criteria that are commonly considered as constraints to the P4S problem. The three categories of data quality criteria include 1) completeness, 2) accuracy and spatial resolution, and 3) 'registrability'. The prior P4S works are then reviewed in a structured way by contrasting them in the way they formulate the P4S optimisation problem: the type of inputs they assume (model and possible scanning locations), the constraints they consider, and the algorithm they utilise to solve the optimisation problem. This work makes two contributions: (1) it identifies gaps in knowledge that require further research such as the need to establish a fully automated scan plan which provides the optimum coverage in construction domain specifically for indoor construction; and (2) it provides a framework — principally a set of criteria — for others to compare new P4S methods against the existing state of the art in the field. This will not only be valuable for young researchers who want to start research in solving the P4S problem, but also for the ones already working in the domain to rethink the problem from different perspectives. • We review of need for planning for (laser) scanning (P4S) in construction. • We propose to categorise point cloud quality measures in 3 groups. • The groups are: completeness, accuracy, and registrability. • We compare prior P4S works based on inputs, constraints, and solving algorithms. • We identify gaps in knowledge to be considered for future research. [ABSTRACT FROM AUTHOR]