Integration of Building Information Model into a Game Engine

Platform for Indoor Accessibility Analyses

KORAY AKSU , HANDE DEMIREL

Faculty of Civil Engineering, Department of Geomatics Engineering,

Istanbul Technical University,

Ayazaga Campus, Maslak, Istanbul, 34469,

TURKEY

Abstract: - Understanding the movement patterns of individuals within a structure is crucial for efficient

simulation. This entails the examination of network accessibility based on insights into the intricate indoor

three-dimensional network topology. The combination of Building Information Modeling with Game Engines

can streamline this approach. Hence, this study proposes a pipeline integrating the A* shortest path algorithm

and walkable three-dimensional navigation meshes to analyze indoor accessibility. The pipeline design was

deployed in a public building, where scenario-based analyses were conducted to determine the average distance

and time shifts based on blockages. According to the results, exits' positioning and availability significantly

impact indoor navigation and accessibility, underscoring their significance in building design and emergency

preparedness in complex buildings.

Key-Words: - Indoor Accessibility, Shortest Path, Game Engine, BIM, 3D Modeling, A* Algorithm.

Received: August 12, 2023. Revised: May 21, 2024. Accepted: June 24, 2024. Published: July 22, 2024.

1 Introduction

The utilization of three-dimensional (3D) object

models has become widespread across various

industries. These models serve as a digital basis for

digital twins, smart cities, and decision-making

systems, [1]. One of the most common application

areas is the Building Information Model (BIM),

which enables object-based 3D designs, provides a

collaborative workspace, and establishes

connections between buildings' geometric and

semantic information, [2]. Hence, BIM has become

crucial to the Engineering, Architecture, and

Construction (AEC) industry. Furthermore, thanks

to the geometric and semantic information it

contains, BIM creates a spatial data infrastructure

for 3D spatial analysis, visualization, and virtual

reality, [3]. Among other applications, realistic

scenario building has become very popular in

current studies since real-life situations in a digital

environment could be mimicked, saving time, cost,

and labor, where real-life risks are abandoned.

Therefore, the use of BIM in simulation studies

comes to the fore regarding compatibility with real-

life scenarios, [4], [5], [6], [7]. For example,

evacuation scenarios for complex buildings require

such a realistic digital environment due to risks that

include, [8]. To represent the movement of people,

which is one of the basic components of this type of

real-life simulation, in the model, the network

topology must be defined in the simulation

environment, [9]. Network topology refers to the

arrangement of elements in a building, such as

rooms, corridors, and staircases, as well as how they

are connected. Understanding network topology for

efficient space utilization, emergency planning, and

indoor navigation is essential, [10], [11].

Furthermore, shortest-path algorithms are

necessary to simulate the evacuation scenarios.

Well-established and preferred algorithms for the

shortest path are A*, Dijkstra's, and Bellman-Ford,

[12]. The algorithms rely on the topological

relationship between edges and nodes, requiring a

navigation surface to function correctly. The

efficiency of such algorithms depends upon cost

parameters such as time and distance. Navigation

surfaces are also critical for understanding

movement within a building, where semantic

information is incorporated. It aids in designing

accessible and efficient routes, which is particularly

important for large or complex structures.

Integrating BIM with game engines allows for

detailed analysis of network topology and the

creation of optimized navigation surfaces, which

enhances building functionality and safety. This is

possible by creating a 3D environment where

different scenarios can be simulated and evaluated,

providing a more interactive and engaging way to

analyze and present complex data, [13], [14].

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Koray Aksu, Hande Demirel

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Several integration challenges exist, such as the

Industry Foundation Classes (IFC) data model

developed by BuildingSMART, which provides a

standard data schema that integrates various data

sources, [15], [16], [17]. Although several studies

exist to generate navigation models from BIM and

use the IFC international standard, [18], [19], [20],

[21] a limited number of studies show that it

integrates an A* shortest path algorithm and

walkable 3D navigation meshes that could be

retrieved from game engine platforms. The A*

shortest path algorithm is preferred within this study

due to ease of use and maturity since this study

emphasizes generating 3D networks. Furthermore,

within this study, 3D indoor accessibility is

analyzed, which can only be achieved via

integrating BIM and Game Engine technologies.

The study aims to integrate BIM into a game engine

platform for 3D indoor network analyses. The

developed easy-to-use pipeline, which integrates the

A* shortest path algorithm and walkable three-

dimensional navigation meshes, was implemented in

a public building. Scenario-based analyses were

conducted to detect average distance changes and

time changes, demonstrating that the developed

pipeline is valid for practical applications. This

integration serves as a 3D digital basis for digital

twins, smart cities, and knowledge-based decision-

making systems, where it highlights its potential in

real-world settings. This manuscript is structured as

follows: Section 2 presents the case study area, the

data used, and the methodology. Section 3 discusses

the achieved results and elaborates on future studies;

finally, the study concludes in Section 4.

2 Data and Methodology

The developed pipeline consists of three stages:

BIM into a game engine, defining navigation

surfaces, and performing accessibility. All pipeline

stages are illustrated in Figure 1. Within the first

stage, a BIM model needs to be generated, where at

least the Level of Detail (LoD) of 300 is suggested.

This model could be generated from 2D CAD

models or spatial data acquisition techniques such as

laser scanning, photogrammetry, and image

processing. Furthermore, commercial and open-

source software such as Autodesk Revit, Archicad,

and Blender are available. The generated BIM is

transferred to the game engine environment. In the

second stage, the navigation surface is created

within the game engine platform. A navigation

surface must be created to ensure the movement of

the characters in the model. For this, walkability

information (walkable/non-walkable) on the surface

of the objects must be added to the model. Hence,

walkable and non-walkable surfaces are defined,

and the required surfaces for 3D network analysis

are produced. In the third stage, network analyses

are carried out. At this stage, the origin and

destination points need to be defined. Then, the

shortest paths between the origin and destination

points are calculated by applying the A* shortest

path algorithm to the navigation surface generated

in the second stage. To validate the developed

concepts, a case study area is selected which is the

Istanbul Technical University, Faculty of Civil

Engineering building in Türkiye. The building is a

public building that includes laboratories,

classrooms, and offices and has five floors. The

building consists of four blocks, each containing 3-5

floors. The floor heights range from 3 to 4.5 meters,

including the intermediate floors.

Fig. 1: The pipeline for BIM and game engine

platform integration

A BIM of the Faculty of Civil Engineering in

Level of Detail (LoD) 300 was modeled in a

research project that the authors conducted, [22].

The BIM includes approximately 500 tagged rooms,

including classrooms, offices, toilets, corridors,

warehouses, and archives. The BIM model of the

study area in the Unity3D environment is shown in

Figure 2.

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Fig. 2: BIM of the study area

3 Result and Discussion

The designed pipeline was successfully

implemented in the case study area. The detailed

BIM is integrated into the Unity3D environment

using the IFC international standard. Navigation

surfaces were created by adding walkability

information about the objects in this context. The

walkability status of each element is illustrated in

Table 1. Each entity of the BIM is assigned to an

IFC class, where the walkability status is also

provided. After defining the walkable and non-

walkable surfaces, a 3D navigation network is

generated in the game engine environment,

illustrated in Figure 3.

Table 1. Walkability status of IFC entities to define

navigation mesh

Entity

IFC Class

“IfcBuildingElement”

Walkability

status

Column

IfcColumn

Door

IfcDoor

Floor

IfcSlab

�

Stair

IfcStair

�

Wall

IfcWall

Window

IfcWindow

Fig. 3: Navigation surface on the floor in blue color

The last stage of the pipeline is conducting the

network accessibility analyses within the building.

For this purpose, origin and destination points need

to be defined. To test the pipeline, a centroid is

assigned to each building corridor as its origin.

Two distinct exits were designated as destination

points. The location of the origins, destinations, and

building exits is shown in Figure 4.

Fig. 4: Location of the origins (red points) and

destinations (exits) on 2D view

Detailed 3D network accessibility analyses are

performed by defining different scenarios to

evaluate the building's accessibility status. Three

scenarios were defined to determine average

distance and time using the A* shortest path

algorithm. The average speed of the actor at the

centroid in the simulation environment is defined as

≈4 m/s. The 3D route of the actor in the building is

presented in Figure 5, where the orange points

show the initial position of the actors at the origin,

and the black point shows the exit point, which was

previously defined as the destination. Within the

figure, the red line shows the 3D shortest path of

related origin points.

Fig. 5: 3D shortest path in the red line

The reference scenario, scenario 1, is illustrated

in Table 2. The average distance and time taken to

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reach the exit from the corridors were calculated

when both were accessible.

Table 2. All exits are accessible (Scenario 1)

Origin

point

Average

distance (m)

Average

time (s)

1st Floor

39.66

10.5

2nd Floor

45.55

12.3

3rd Floor

69.48

19.8

4th Floor

64.93

19.7

5th Floor

71.19

22.0

According to scenario 2, only Exit 1 is

accessible, whereas Exit 2 is blocked. The average

distance and time it takes to reach Exit 1 from the

corridors were calculated. The results are illustrated

in Table 3. It was observed that the average time

and distance increased with the height of the floors

and that the 3rd and 4th floors had similar values.

Furthermore, it was observed that the distances and

times of the 1st floor and 2nd floor, as well as the 4th

floor and 5th floor, were similar.

Table 3. Only Exit 1 is accessible (Scenario 2)

Origin

point

Average

distance (m)

Average

time (s)

1st Floor

71.55

20.0

2nd Floor

75.40

20.8

3rd Floor

100.80

28.8

4th Floor

116.35

36.7

5th Floor

129.49

38.0

According to scenario 3, only Exit 2 is

accessible, whereas Exit 1 is blocked. The average

times and distances for the 3rd floor and 4th Floor

were similar, as shown in Table 4.

Table 4. Only Exit 2 is accessible (Scenario 3)

Origin

point

Average

distance (m)

Average

time (s)

1st Floor

64.23

17.0

2nd Floor

72.50

20.0

3rd Floor

81.90

23.5

4th Floor

81.34

23.3

5th Floor

71.19

22.0

A detailed comparison table is provided in

Table 5. Scenario 2 and Scenario 3 are compared to

the reference scenario, Scenario 1, concerning

average distance and time. When Exit 1 was

blocked, the average distance and time to the origin

point on the 1st and 5th floors increased by

approximately 80-82%, and these floors showed the

highest increase compared to the other floors.

When Exit 2 was blocked, the average distance and

time to the origin point on the 1st and 2nd floors

increased by approximately 59-62%, and these

floors showed the highest increase compared to the

other floors. For the 5th floor, the change in

accessibility is insignificant for both scenarios.

Table 5. Change of average distance and time of

Scenario 2 and Scenario 3 with respect to Scenario

Origin point

Change of

distance (%)

Change of

time (%)

(Scenario 2 | 3)

1st Floor

80 | 62

90 | 62

2nd Floor

66 | 59

69 | 63

3rd Floor

45 | 18

46 | 19

4th Floor

79 | 25

86 | 19

5th Floor

82 | 0

72 | 0

The following information should be carefully

interpreted based on its intended use. For instance,

in the event of a building evacuation due to fire,

time is of the essence as fire and smoke can have

severe impacts on human health. It is important to

have sufficient routes with adequate capacity and

minimal travel distance leading to safe areas, as

well as escape routes and early warning systems

[23]. The necessary time to evacuate the building

safety is depending on a very large number of

parameters such as capacity of the building,

material used, measures to detect fire, etc.

Additionally, it is crucial to model human

behaviors, as there have been significant

advancements in simulation platforms. This

information is valuable for decision-makers when

planning preventive maintenance actions to

mitigate the risks of fire and earthquakes.

By deploying the designed pipeline, the

traditional 2D navigation network is transformed

into a 3D navigational network incorporated into

the game engine environment. Furthermore, a non-

complex shortest-path algorithm is implemented

into the pipeline to support co-creation, co-design,

and co-implementation during the emergency

preparations of complex buildings. The developed

concepts could be further enriched via 3D network

connectivity analyses, incorporation of human

behaviors via agent-based platforms, and

integration of indoor and outdoor models.

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4 Conclusion

According to recent developments in simulation

environments, it is possible to generate more

realistic 3D navigation accessibility analyses to aid

decision-makers in building design and emergency

planning. For this purpose, an easy-to-use pipeline

is designed and validated that incorporates a

detailed BIM, a game engine environment, and

accessibility analyses. According to the results,

building design and emergency scenarios could be

revisited, where the designed pipeline could serve

as a 3D digital basis for digital twins, smart cities,

and knowledge-based decision-making systems.

This integration not only allows for more

comprehensive spatial accessibility analyses to be

performed but also opens up new possibilities for

the future of indoor accessibility research.

Acknowledgments:

The study is supported by The Scientific and

Technological Research Council of Türkiye

(TÜBİTAK). (Building Information Model Based

Fire Evacuation Simulation, Project No. 121Y099).

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Contribution of Individual Authors to the

Creation of a Scientific Article (Ghostwriting

Policy)

- Koray Aksu: Methodology, Testing, Writing

- Hande Demirel: Methodology, Writing, Review

Sources of Funding for Research Presented in a

Scientific Article or Scientific Article Itself

The study is supported by The Scientific and

Technological Research Council of Türkiye

(TÜBİTAK). (Building Information Model Based

Fire Evacuation Simulation, Project No. 121Y099).

Conflict of Interest

The authors have no conflicts of interest to declare.

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(Attribution 4.0 International, CC BY 4.0)

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Creative Commons Attribution License 4.0

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DOI: 10.37394/232015.2024.20.36

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396

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