3D Urban Environment Research Articles

Voxel based volumetric visibility analysis of urban environments

The objective of this work is to develop integrated volumetric visibility analysis and modelling for environmental and urban systems. This work involves interdisciplinary research efforts that focus primarily on architecture design discipline and Geoinformatics. The work integrates an advanced Spatial Openness Index (SOI) model within a realistic geo-visualised Geographical Information System (GIS) environment. It is based on the assumption that the measured volume of visible space can indicate the perceived density. Most previous work aimed at computing visibility in open terrain and was based on the common Line of Sight (LOS) approach. Open terrain is usually defined as a 2·5D Digital Elevation Model (DEM) and the visibility analysis is carried out by computing profiles from a view point to all the DEM points. Applying the DEM/LOS method in a 3D urban environment causes severe difficulties: a 2·5D DEM structure is unable to accurately model 3D objects (and especially complex buildings), exact visibility computation is a long process and requires a very detailed scanning of the 3D objects. Accordingly, and in order to bypass these difficulties, a new approach has been developed – an approach which is based on subdividing the urban environment volume into voxels (volume elements, representing a value on a regular grid in 3D space). Implementing a spatial intersection between the buildings and the 3D grid of voxels on the one hand, and applying a sophisticated computation sequence of one-time handling a voxel on the other, enables the efficient computation of the visibility in a fast, flexible and accurate process. Moreover, in contrast to the common approach of a binary visibility decision – a point can be visible versus invisible; the suggested approach enables to compute visibility as a continuous figure with in-between values from fully visible up to fully invisible. This visibility model measures the volume of visible space at any required view point. This model enables accurate 3D simulation of the built environment regarding built structure and surrounding vegetation. A 3D model of our case-study, the Neve-Shaanan neighborhood in Haifa, was developed. The paper introduces the model, explains its main attributes and demonstrates the procedure of evaluating/measuring a realistic built environment. The model is planned to be assessed using subjective residents’ evaluation. The results of this research have shown its potential contribution to professional users, such as researchers, designers and city planners, at the same time as being easily used by non-professionals such as city dwellers, contractors and developers.

TRANSFORMING 2D CADASTRAL DATA INTO A DYNAMIC SMART 3D MODEL

Abstract. 3D property registration has become an imperative need in order to optimally reflect all complex cases of the multilayer reality of property rights and restrictions, revealing their vertical component. This paper refers to the potentials and multiple applications of 3D cadastral systems and explores the current state-of-the art, especially the available software with which 3D visualization can be achieved. Within this context, the Hellenic Cadastre's current state is investigated, in particular its data modeling frame. Presenting the methodologies and specifications addressing the registration of 3D properties, the operating cadastral system's shortcomings and merits are pointed out. Nonetheless, current technological advances as well as the availability of sophisticated software packages (proprietary or open source) call for 3D modeling. In order to register and visualize the complex reality in 3D, Esri's CityEngine modeling software has been used, which is specialized in the generation of 3D urban environments, transforming 2D GIS Data into Smart 3D City Models. The application of the 3D model concerns the Campus of the National Technical University of Athens, in which a complex ownership status is established along with approved special zoning regulations. The 3D model was built using different parameters based on input data, derived from cadastral and urban planning datasets, as well as legal documents and architectural plans. The process resulted in a final 3D model, optimally describing the cadastral situation and built environment and proved to be a good practice example of 3D visualization.

Fast and efficient visible trajectories planning for the Dubins UAV model in 3D built-up environments

SUMMARYIn this paper, we study the visible trajectories planning for unmanned aerial vehicles (UAVs) modeled with a Dubins airplane in 3D urban environments. Our method is based on a fast and exact spatial visibility analysis of the 3D visibility problem from a viewpoint in 3D built-up environments. We consider the 3D urban environment buildings modeled as cubes (3D boxes) and present an analytic solution to the visibility problem. Based on an analytic solution, the algorithm computes the exact visible and hidden parts from a viewpoint in the urban environment. We present a local trajectory planner generating the most visible trajectory in a known 3D urban environment model, taking into account the dynamic and kinematic UAV constraints. The planner computes, at each time step, the next UAV's attainable velocities and explores the most visible node, while avoiding buildings as static obstacles in the environments, using the velocity obstacle method. The visibility type of the trajectory can be configured beforehand as visible roofs and surfaces in the environments. We demonstrate our visibility and trajectory planning method in simulations in several 3D urban environments, showing visible trajectory planning capabilities.

COREGISTRATION OF DSM AND 3D POINT CLOUDS ACQUIRED BY A MOBILE MAPPING SYSTEM

The development of 3D mapping databases is a matter of increasing interest. Databases have recently been developed at different scales (national, European, international) and to meet different needs. Such development has been made possible by the implementation of efficient 3D mapping technologies. 3D mapping strategies are based on multi-sensor data fusion usually performed after a preprocessing step that includes registration and filtering. In this paper, we present our work on registration methods applied to solve problems in 3D urban environment representations issued from a Mobile Mapping System. We improve the stability of convergence, the computation time and handle heterogeneous data sets in various scenarios.

A new approach to create textured urban models through genetic algorithms

The automatic process for texturing 3D urban environments realistically is a challenging topic in Computer Graphics, especially when the model is generated from 2D GIS data from real sites. In order to achieve realistic scenes, buildings, urban furniture and street roadways should be modeled automatically also considering the slope of steep streets. A texturing process by hand which takes into account all the urban elements of a city is an impracticable task, especially if quality results are required.In this paper we propose an automatic method for building texturization in entire urban models using a small set of images. The different features of lower and upper parts of buildings are considered by implementing two different genetic algorithms. Our method can be used in cities with both horizontal and steep streets because the street slope is processed by the algorithm.

An agent-based model and computational framework for counter-terrorism and public safety based on swarm intelligencea

Public safety has been a great concern in recent years as terrorism occurs everywhere. When a public event is held in an urban environment like Olympic games or soccer games, it is important to keep the public safe and at the same time, to have a specific plan to control and rescue the public in the case of a terrorist attack. In order to better position public safety in communities against potential threats, it is of utmost importance to identify existing gaps, define priorities and focus on developing approaches to address those. In this paper, we present a system which aims at providing a decision support, threats response planning and risk assessment. Threats can be in the form of Chemical, Biological, Radiological, Nuclear and Explosive (CBRNE) weapons and technologies. In order to assess and manage possible risks of such attacks, we have developed a computational framework of simulating terrorist attacks, crowd behaviors, and police or safety guards’ rescue missions. The characteristics of crowd behaviors are modeled based on social science research findings and our own virtual environment experiments with real human participants. Based on gender and age, a person has a different behavioral characteristic. Our framework is based on swarm intelligence and agent-based modeling, which allows us to create a large number of people with specific behavioral characteristics. Different test scenarios can be created by importing or creating 3D urban environments and putting certain terrorist attacks (such as bombs or toxic gas) on specific locations and time-lines.

Focus+Context Route Zooming and Information Overlay in 3D Urban Environments

In this paper we present a novel focus+context zooming technique, which allows users to zoom into a route and its associated landmarks in a 3D urban environment from a 45-degree bird's-eye view. Through the creative utilization of the empty space in an urban environment, our technique can informatively reveal the focus region and minimize distortions to the context buildings. We first create more empty space in the 2D map by broadening the road with an adapted seam carving algorithm. A grid-based zooming technique is then used to enlarge the landmarks to reclaim the created empty space and thus reduce distortions to the other parts. Finally, an occlusion-free route visualization scheme adaptively scales the buildings occluding the route to make the route always visible to users. Our method can be conveniently integrated into Google Earth and Virtual Earth to provide seamless route zooming and help users better explore a city and plan their tours. It can also be used in other applications such as information overlay to a virtual city.

Hierarchical lane‐oriented 3D road‐network model

The existing road‐network models based on the 2D link‐node of roadway centrelines have inhibited lane‐oriented network flow analysis and multi‐dimensional inventory management in complicated 3D urban environments. This paper proposes a hierarchical lane‐oriented 3D road‐network model (HL‐3DRNM), with a unified modelling language (UML) diagram. HL‐3DRNM is a non‐planar topological model with the support of a 3D lane ribbon cartographic display, which is characterized by: (1) multiple topological and cartographic representations and various abstraction levels (street, road segment, carriageway and lane); and (2) referenced multi‐dimensional road information (point, line, area and volume) at lane level. HL‐3DRNM provides solid mathematical foundations for a more detailed inventory management, effective network analysis and realistic navigation in the increasingly complicated 3D urban transportation systems.

The implications of inter-visibility between landmarks on wayfinding performance: An investigation using a virtual urban environment

We investigated the effect of inter-visibility conditions between landmark elements in a simulated 3D urban environment on wayfinding performance (the acquisition of spatial knowledge through direct experience within the simulated environment and navigation throughout this environment). Our experiment was conducted by means of a 3D virtual environment to test the effect of two properties of visibility conditions: the overlapping between the visual fields of two landmarks and the topological depth (length of visual chain) between these visual fields. The results show that a high degree of overlapping between the visual fields of an origin and a target landmark helps people perform wayfinding tasks, particularly in cases where the length of the visual chain is short (one-step topological depth).