Combining Open Source and Commercial Tools in Digital Twin for Cities Generation

Evidently, Smart Cities are on the rise and there is an increasing need for digital twins of these complex environments and their corresponding 3D models. The creation and maintenance of such twins is a time consuming task, since cities are living evolving organisms. In this paper we are presenting work done within the Digital Twin Cities Centre (DTCC) in Sweden in the field of automated 3D city model generation. We showcase a novel method of combining open source and commercial software for creating digital twins of any urban context in a procedural way from raw input data and using Unreal Engine as a visualization front-end. We combine two different workflows, one based on the commercial software suite Feature Manipulation Engine and in parallel we utilize the open source code developed within the Centre, dubbed DTCC Builder. The assets created can be used in urban planning, multiphysics continuum mechanics simulations and for visualization and illustration on a 3D scale. By using, in a complementary way, established commercial software and state of the art open source C++ code we manage to utilize the quality of life features the first provides, while assigning the demanding tasks of comforming mesh generation to the former. The longer term goal is (nearly) real-time mesh digital twinning of any city and user interaction with the 3D assets provided. Copyright (C) 2022 The Authors

CFD Simulation and 3D Visualization on Cultural Heritage sites: The Castle of Mytilene

This paper presents a CFD and 3D Visualization pipeline to simulate wind flow over a heritage site and then visualize the results. As case study, a coarse 3D geometry model of the Fortress of Mytilene, Lesvos island, Greece and its surrounding was generated from open access Digital Elevation Models. The CFD simulation of the air flow on the wider heritage site area was performed using the steady-state version of the in-house flow solver IBOFlow (Immersed Boundary Octree Flow Solver) developed at Fraunhofer-Chalmers Research Centre. All the simulations were completed considering the mean wind direction and wind speed during the last 22 years from actual weather data retrieved from Open Weather Map. The visualization results were achieved through Unreal Engine, using built-in visualization tools and a tailored-made plugin to visualize the air flow over the monument and on the monument’s wall. As discussed in the conclusion section, the overall process proposed in this paper can be implemented for an initial assessment of the effect of environmental parameters over any heritage site and moreover, it may form the basis for valuable assistive tool for conservators and engineers

Visualisation of traffic noise exposure and health impact in a 3D urban environment

It is becoming increasingly common to work with urban planning using 3D visualisation tools. In the project DemoVirPEN a research team with participation from different research fields cooperated to create a demonstration concept for visualising traffic noise and the associated health impact in a 3D graphics environment. The project included participation from the following fields; 3D modelling and mapping, traffic noise calculation, auralisation, urban planning and architecture and health impact of noise exposure. The final product of the project is summarised in a film clip that illustrates the main results by visualising and auralising traffic in different configurations from different perspectives. A few key points are visualising short time frames (single vehicle passage) versus yearly average (noise map), and impact of changes such as removing or modifying traffic flows and buildings

An urban planning tool demonstrator with auralisation and visualisation of the sound environment

The paper presents findings from a recent project about the development of a demonstrator of an urban planning tool that includes auralised sounds as well as visualisations of sound propagation and facade noise levels linked to health impact. In urban development projects, the sound environment is one of the key elements, but often enters late in the planning process. As a result, even if the noise regulations are fulfilled, the potentially good sound environment may suffer unnecessary quality reductions. In addition, the standard ways of presenting and analysing the situations, using noise levels and noise maps, has potential for improvement, especially considering the transdisciplinary approaches to planning that are increasing in use. The tool aims to simplify the usage also at early stage planning, including scenario analysis, as well as to facilitate the urban planners\u27 understanding of the sound environment and its effects. The paper presents results from the development of the demonstrator, reflecting on auralisation as well as on multiple aspects of visualisation including grid noise maps, health-related facade noise levels and choice of colour scales

Visual conflicts - Challenges in combining rich volumetric 3D-data in a realistic VR city model

This paper presents a work in progress on how to visualize the impact of vegetation on urban air quality in a virtual city model, explorable using virtual reality (VR). The transdisciplinary project CityAirSim - Visualizing and modelling urban air quality - influence of vegetation, building morphology and traffic emissions develops a modelling framework to simulate the effects of vegetation, buildings and traffic strategies on air pollution, in order to understand the synergies and conflicts between these factors. The resulting data will be visualized in a VR-application allowing interactive exploration. Two primary target groups for the VR-application are high school students and urban planners. We aim for the tool to be used in teaching, e.g., in environmental science, as well as in communication with the public in exhibition environments, such as science centers. This paper focuses on how we should visualize invisible air pollution in an otherwise realistic urban setting to facilitate understanding. One important aspect to consider is to create a visual balance between data visualization and the visualization of the built environment in the model. Another aspect is to define the appropriate levels of data visualization and abstraction of representation to use, without losing richness of information