Savioja - Utilizing Virtual Environments In Construction Projects.pdf - Akustyka(1) - dzidzia2603

UTILIZING VIRTUAL ENVIRONMENTS IN CONSTRUCTION

PROJECTS

SUBMITTED: August 2002

REVISED: January 2003

PUBLISHED: May 2003 at http://www.itcon.org/2003/7

EDITOR: Kalle Kahkonen

Lauri Savioja, Professor,

Telecommunications Software and Multimedia Laboratory, Helsinki University of Technology, Fi

email: Lauri.Savioja@hut.fi, http://www.tml.hut.fi/~las/

Markku Mantere,

Telecommunications Software and Multimedia Laboratory, Helsinki University of Technology, Fi

email: Markku.Mantere@hut.fi

Iikka Olli,

Telecommunications Software and Multimedia Laboratory, Helsinki University of Technology, Fi

email: Iikka.Olli@hut.fi

Seppo Äyräväinen,

Telecommunications Software and Multimedia Laboratory, Helsinki University of Technology, Fi

email: Seppo.Ayravainen@hut.fi

Matti Gröhn,

Telecommunications Software and Multimedia Laboratory, Helsinki University of Technology, Fi

email: Matti.Grohn@hut.fi

Jyrki Iso-Aho

A-konsultit, Helsinki, Fi

email: jyrki.iso-aho@a-konsultit.fi

SUMMARY: Construction projects can gain major benefits from application of virtual environments. The

virtual reality techniques help designers to communicate with each other, as well as with the decision makers

and with the end-users. In the future, the whole product model of a new building should form one virtual

building, which can be efficiently investigated utilizing virtual environments. In this article we present some

basics of virtual reality technology, and the required software and hardware components from the viewpoint of a

construction project. The main emphasis of the article is in the description of the construction project of a new

lecture hall at the Helsinki University of Technology, and how a virtual environment was utilized in that project.

KEYWORDS : Virtual environments, virtual reality, visualization, construction project

1. INTRODUCTION

Virtual reality (VR) has been an active field of research during the past decade. The goal of VR is to mimic the

nature such that – at the best – users can’t distinguish between reality and virtual reality. Although we are still far

from the perfect illusion, quite convincing visual, aural, and haptic techniques have been developed to achieve

this ultimate goal. Despite all the research, only few practical applications of VR exist. One quite obvious

application area is architectural visualization. In a more general level, entire construction projects can gain major

benefits from utilizing VR.

1.1 A 3D product model in building design

A model of a building may be constructed merely for presentations at a VR system, but utilization of VR really

becomes a meaningful and effective part of the working process, when the idea of a product model is used in the

ITcon Vol. 8 (2003); Savioja et al., pg. 85

design process. The idea of a product model is to combine separate drawings into one virtual building. A

traditional drawing becomes merely a view to the model at a chosen moment, whereas the whole building and its

environment are included in one single product model. Everything is modeled three-dimensionally (3D), and the

model is maintained throughout the project from start to hand-over.

Among the benefits of the product model compared to traditional methods is that one can easily produce

simulations and presentations applying VR to support project decision. In addition, it provides 3D-information

for the needs of the various consultants; bills of quantities for cost control, geometric and structural properties

for the life cycle and cost analyses of project alternatives. The product model is also a direct source of

construction documents and production 4D-planning. Utilizing VR technologies could be a natural part of the

product model working method in the future.

1.2 Objectives of this article

We have two main objectives for this article. From the architectural point of view, our goal is to describe the

possibilities opened up by virtual environments for construction projects. From the technical point of view, we

aim to present kinds of software and hardware required for successful application of a virtual environment in a

case study.

As a case study, we present results achieved in one particular construction project: the construction of a new

large lecture hall in the main building of the Helsinki University of Technology (HUT). The virtual environment

at the Telecommunications Software and Multimedia Laboratory (TML) at the HUT was actively utilized

throughout the process, from the first drafts to the opening of the new hall (Gröhn et al., 2001b).

1.3 Organization of the article

The article is organized as follows: Section 2 gives a short overview of virtual reality technologies, and the

facilities at the HUT are described in more detail. Section 3 presents the possibilities provided by VR from the

architectural point of view. The case study is presented in Section 4. The main emphasis is on the applied models

and the parties involved in the project, as well as in their mutual interaction. Section 5 concludes the article.

2. VIRTUAL REALITY TEHCNOLOGIES

VR technology is a wide topic, covering a variety of techniques and devices. In this section, we give a brief

overview of the most important factors to be taken into account when designing a VR system. The same

principles apply to the design of models to be presented with a VR system. Such models are called virtual worlds

in this article.

At the HUT we have a virtual environment called the Experimental Virtual Environment (EVE). Software and

hardware utilized in the EVE are described in this section. In terms of this article, the VR systems similar to the

EVE are called virtual environments.

2.1 Overview of virtual reality technologies

Ivan Sutherland introduced his vision of a virtual world in his article “Ultimate Display” in 1965 (Sutherland,

1965). According to him, the main challenges in the creation of a virtual world are to make it look real, sound

real, feel real, and respond realistically to user's actions. He successfully summed up the main objectives of

implementation of a VR system. It is impossible to implement a perfect one with current technology. Thus the

objective is to make the system as immersive as possible by concentrating on the most relevant issues.

2.1.1 Look real

To make a virtual world look real, it must be carefully modeled. Surface materials, small details, and lighting are

crucial in creating a realistic environment. Small movement, like trees and leaves swaying in the wind, greatly

add to the experience. Any movement in the world must obey the principles of physics to appear realistic. In

addition, the visible world should cover a large field of view, and respond realistically to the user’s movements.

The user should be able to feel the dimensions of the environment. This is typically done by presenting the view

to the virtual world stereoscopically, i.e. from a slightly different position for each eye.

ITcon Vol. 8 (2003); Savioja et al., pg. 86

Current modeling and animation software enables the creation of realistic-looking virtual worlds, which can even

be animated. Typically, these virtual worlds can be pre-rendered, and displayed in a wide screen – even

stereoscopically – to create an immersive experience. However, the view must be created in real-time when the

user is allowed to move freely in the virtual world. This requirement limits the allowed complexity of the model,

forcing modelers to concentrate on the most essential factors. Since small details and accurate lighting are

perceptually significant but computationally expensive to render in real-time, they are typically pre-rendered as

textures. For example, the lighting conditions in the surfaces of an architectural scene are often saved as textures

using a computationally intensive radiosity method.

Stereoscopic viewing requires a different image to be presented for each eye, which can be accomplished in

many ways. One method is to use a head-mounted display (HMD), which has two small displays, one for each

eye. Optionally a sensor can be attached to HMD to register the movement of the head. HMD can be used to

create an immersive environment for one user at a time. Another method is to use a spatially immersive display

(SID) – a large display with special glasses for separating the images for each eye. The glasses can be either

passive, including red/blue, red/green, and polarizing filters – or active, like LCD shutter glasses. The use of

passive glasses requires displaying two images at a time, while with active glasses, the images are displayed

alternately for each eye. The third method for displaying stereoscopic images is called autostereoscopy. It does

not require any special glasses. However, autostereoscopic methods are often otherwise restrictive; they have a

limited viewable region, small resolution, or bad image quality. Most autostereoscopic displays are quite

complex and expensive to manufacture, and their typical size is no larger than a normal television set.

2.1.2 Sound real

For an immersive VR experience, a 3D soundscape needs to be created. 3D audio enhances the sense of

presence. In addition, it can be utilized in other tasks such as localization, navigation and data presentation

(Gröhn et al., 2001a). 3D sound can be produced using either binaural or multichannel techniques. In binaural

3D sound reproduction techniques, the principle is to control the sound signal in the entrances of the listener's

ear canals as accurately as possible. For one user this requirement is in practice easiest to fulfill with headphones

using head-related transfer functions (HRTFs) (Begault, 1994, p. 52). HRTF-reproduction is the most convenient

combination with HMDs.

In a multi-user situation, loudspeakers are more convenient than headphones. One commonly employed method

for multichannel loudspeaker reproduction is vector base amplitude panning (VBAP) (Pulkki, 1997). To enable

arbitrary positioning of sound sources VBAP uses three nearest loudspeakers for one sound.

To make a virtual world sound real the acoustics of the virtual world should be simulated in real-time. In general,

the modeling is based on knowledge of sound sources, room geometry, and acoustical properties of materials

(Savioja et al., 1999).

2.1.3 Feel real

To make a virtual world feel real, the user must be able to touch virtual objects. If the user sees a virtual table or

chair, but cannot touch it, the immersion is reduced. When the user picks up a virtual ball, he should be able to

feel, whether the surface is rough or smooth, and whether the ball is soft or hard. These two cases are called

haptic and force feedback. Both of these fields are currently under active research. Haptic devices are still quite

immature, case-specific, and expensive, while force feedback is currently used even in consumer-level products

such as joysticks, steering wheels, and gamepads.

2.1.4 Respond realistically to user's actions

To respond to the user's actions realistically, the movements of his body, head, hands and feet must be tracked.

The system must be very responsive to the user’s actions, i.e. it must have a low latency, or the immersion will

suffer. The consequences of the actions of the user must obey the principles of the physics in the virtual world.

This requires, at least, detecting the collisions between the user and the virtual objects. In practice, only some

parts of the user are tracked, a noticeable latency exists in the system, and the physics model is – at best –

incomplete.

There are many techniques to track the user. The oldest technique is mechanical tracking. The body part to be

tracked is attached to a construction with sensor-fitted joints. This is an accurate and fast method, but typically

ITcon Vol. 8 (2003); Savioja et al., pg. 87

considerably hinders user’s movement. Magnetic tracking systems are currently the most commonly applied

ones. They have receivers for measuring either AC or DC magnetic field, generated by a transmitter. Magnetic

tracking systems are quite accurate, but they are subject to distortion from external electromagnetic fields. There

are also tracking systems based on optical recognition, inertia, and ultrasound. Each of these methods has its

strengths and weaknesses. Also systems utilizing several of these techniques exist. These systems are called

hybrid systems.

2.1.5 The reality of current virtual reality techniques

Although the capacity of modern computer systems keeps increasing rapidly, a perfect VR system remains to be

seen. There are simply too many variables and too many sensors to connect, as well as too much computation to

be done in real-time. There are very complex and advanced systems for specific purposes, but not a single

system for fulfilling the dream of a perfect general-purpose VR system. The technology is just not there – yet.

In spite of the lack of a general-purpose system, there are several types of commercial, versatile, immersive VR

systems available. The systems range from HMDs and small virtual tables to large-scale virtual environments

and beyond. Traditionally virtual environments have been driven by expensive, high-end SGI Onyx computers,

but PC-based systems are becoming more and more popular. In either case, the high quality projectors and

screens required are quite expensive, as well as are high quality HMDs. Some manufacturers of commercial VR

systems are listed in Table 1a nd Table 2.

Table 1: Some of the off-the-shelf immersive virtual reality systems manufacturers and their web sites.

Fakespace

http://www.fakespacesystems.com/

TAN

http://www.tan.de/

Mechdyne

http://www.mechdyne.com/

Barco

http://www.barco.com/

Trimension

http://www.trimension-inc.com/

Table 2: Some of the high-end HMD manufacturers and their web sites.

CAE

http://www.cae.ca/

Kaiser Electro-optics

http://www.keo.com/

General Reality

http://www.genreality.com/

Interactive Imaging Systems

http://www.iisvr.com/

Virtual Research

http://www.virtualresearch.com/

2.2 EVE – Experimental Virtual Environment

The EVE is a virtual environment at the TML. The main principles of the EVE are the same as in the CAVE

(Cave Automatic Virtual Environment), originally presented in 1993 (Cruz-Neira et al., 1993). In the EVE, users

stand in a cube measuring 3×3×3 meters. Three of the faces of the cube have rear-projected screens. Figure 1

illustrates the construction details of the EVE. In addition, we have a magnetic tracking system for tracking the

user. A wand, and two data gloves are the other devices to support user interaction in the EVE.

At the HUT we research technologies applied in virtual environments, especially human-computer interaction

and virtual acoustics. Therefore, we started to develop our own virtual environment, with one screen, in 1997. In

1998 the Computer Science Department moved into a new building, during which the EVE was extended.

Currently the EVE is running with three walls, and the floor.

ITcon Vol. 8 (2003); Savioja et al., pg. 88

Figure 1: EVE – the virtual reality system at the HUT.

2.2.1 Graphics hardware

The main computer of the EVE is a Silicon Graphics (SGI) Onyx2 with 8 CPUs, 2 GB of memory and two

InfiniteReality graphics pipes. The capacity of each pipe is split to produce a stereoscopic image to two screens.

The images for the screens are projected with four ElectroHome Marquee 8500 LC Ultra projectors. To view the

images stereoscopically, we use Crystal Eyes CE2 shutter glasses. The operating system of the main computer is

IRIX that is a UNIX variant implemented by SGI.

2.2.2 Audio hardware

Hardware for sound reproduction in the EVE is built around a PC running Linux operating system. The

computer is used for acoustic modeling and audio signal processing. The audio output from the PC is taken from

two eight-channel ADAT interfaces connected to two eight-channel D/A converters. The current loudspeaker

system in the EVE consists of fourteen Genelec 1029 active monitoring loudspeakers. Multichannel 3D sound

reproduction is implemented with the VBAP technique. For more information on the acoustic design of the space

and the applied sound reproduction techniques see Hiipakka et al. (2001).

2.2.3 Input devices

There are multiple input devices in the EVE to support user interaction. The input is gathered from a mouse, a

keyboard, a wand, a magnetic tracker, and a pair of data gloves. The mouse and the keyboard are simply the

common input devices of the SGI computer. They are not used as input devices inside the EVE, but merely for

system control and for setting some parameters of the applications.

The magnetic tracker is an Ascension MotionStar tracker with six receiver units. It is used to measure the

position and orientation of the users head, hands and body.

ITcon Vol. 8 (2003); Savioja et al., pg. 89

Savioja - Utilizing Virtual Environments In Construction Projects.pdf

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