URBAN CITY PLANNING IN

SEMI-IMMERSIVE VIRTUAL REALITY SYSTEMS

Frank Steinicke, Timo Ropinski, Klaus Hinrichs and J

org Mensmann

Institut f

ur Informatik, WWU M

unster

Einsteinstraße 62, 48149 M

unster, Germany

Keywords:

Urban planning, virtual reality, user interfaces, interaction metaphors.

Abstract:

Virtual reality based geographic information systems (VRGIS) have been successfully employed for urban

planning and architectural design in recent years. Tracking technologies and stereoscopic visualization of

three-dimensional structures allow a better insight into complex datasets. Unfortunately, these systems often

lack intuitive interaction concepts and therefore reduce VRGIS to advanced visualization environments, since

manipulation of the content is not or only rudimentarily possible. In this paper, we present a geographic infor-

mation system for urban planning tasks in semi-immersive virtual reality (VR) systems. The objective of this

approach is to provide professional city planners with an enhanced VR interface, which enables comfortable

interaction concepts similar to the interactions of the real-world planning task. To assure the usability and

relevance of the developed system, urban planners have cooperated closely in the development process. In this

paper both the hard- and software architecture of the entire system as well as VR related interaction metaphors

and their evaluation are discussed.

1 INTRODUCTION

Urban planning tasks are of major importance for civil

works since both the environment and the inhabitants

of a city are affected. The cityscape as well as the

quality of life of the residents essentially depend on

the appearance of buildings, road networks, planting,

green spaces, and recreation areas such as parks and

playgrounds. To facilitate a realistic impression of

how a building area would visually integrate into the

environment and to enable communication regarding

development proposals, it is important to present in-

termediate results of the planning process properly as

well as comprehensible.

Therefore, by using two-dimensional CAD con-

cepts urban planners design development plans for a

certain area based on existing cadastral data, which is

available for every town in Germany. As depicted in

Figure 1 (left) cadastral data usually contains build-

ing footprints, number of ﬂoors and ﬂoor’s height for

each building, parcel boundaries, and other informa-

tion. Within such a development plan, urban planners

deﬁne entities, for example buildings and recreation

areas, associated with a set of constraints, which spec-

ify what types of geobjects are allowed and what re-

quirements have to be incorporated. After urban plan-

ners have agreed to a certain development plan, two

different procedures are commonly used.

One approach is to deliver the development plan to

an architectural ofﬁce. On the basis of this plan archi-

tects generate virtual 3D models and return exemplary

three-dimensional visualizations of these planned ar-

eas to the urban planner. This procedure has the fol-

lowing two major shortcomings. First, the returned

visualizations are static insofar as the 3D models can-

not be explored interactively by the urban planners.

Second, modiﬁcations to the 3D models, which, for

instance, have been proposed after reviewing the 3D

visualization, cannot be performed by urban planners.

Instead, the architectural ofﬁce has to be asked again

to incorporate these modiﬁcations into the 3D model.

During a planning task, this usually takes several iter-

ations resulting in inefﬁciency as well as unnecessary

expense.

The second common alternative to communicate

urban development proposals is to build a physical

block model usually made of wood, plastic or pa-

per. Figure 1 (right) illustrates such a physical block

model for the development plan in Figure 1 (left).

After a physical block model has been ﬁnished, per-

192

Steinicke F., Ropinski T., Hinrichs K. and Mensmann J. (2006).

URBAN CITY PLANNING IN SEMI-IMMERSIVE VIRTUAL REALITY SYSTEMS.

In Proceedings of the First International Conference on Computer Graphics Theory and Applications, pages 192-199

DOI: 10.5220/0001353001920199

 SciTePress

Figure 1: Example section of an urban development plan within cadastral information (left) and a corresponding physical

block model made of wood downscaled to 1:1000 (right).

forming modiﬁcations is often awkward, since most

elements are inﬂexible and ﬁxated to the model, so

that they have to be removed and replaced by new el-

ements. Furthermore, the creation of these models is

a very time consuming task, which requires high ef-

forts in terms of money and manpower. Thus, simpler

solutions to visualize planned development areas are

desired.

In cooperation with the urban development, city

planning and transport planning ofﬁce as well as the

land surveying and land registry ofﬁce of the city of

unster in Germany, we have developed solutions for

these problems. An objective of this cooperation is

to develop computer-aided concepts, which serve the

needs of professional urban planners and provide a

convenient alternative to current planning tasks. Ur-

ban planners demand that the developed strategies

should be based on their current processes resulting in

physical block models as well as computer generated

3D visualizations. However, the city planners desire

to have more independent and sophisticated control

over both approaches; they want to be able to generate

virtual 3D city models and create three-dimensional

visualizations autonomously. Furthermore, the intu-

itive comprehension when viewing a physical block

model should be obtained.

In consideration of these two major demands, we

decided to develop an interactive 3D residential city

planning software system, which runs in virtual re-

ality (VR) systems as well as in desktop-based envi-

ronments. To ensure the adaptation of the planning

system into already existing systems and databases,

a geographic information system (GIS) interface has

been integrated to import the required data. Virtual

reality based geographic information systems (VR-

GIS) are increasingly used for planning tasks, since

VR technologies provide better perception and com-

prehension of complex 3D structures (Beck, 2003).

Unfortunately, these systems often lack intuitive inter-

action concepts and therefore VRGIS are degraded to

exploration systems (Dodge et al., 1998; Beck, 2003).

In order to enhance the interaction in VRGIS we have

developed intuitive interaction metaphors which facil-

itate the efﬁcient design of building plans in a highly-

interactive way.

In this paper, we present the system architecture

and setup of the 3D residential city planning sys-

tem. In particular, we propose advanced concepts for

generic interaction tasks, whose beneﬁts have been

proven in usability studies. The paper is structured

as follows. In Section 2 the table-top-based VR sys-

tem and its beneﬁts are discussed. In Section 3 the

architecture of the interactive 3D residential city plan-

ning software is explained in detail. In Section 4 con-

cepts which facilitate an intuitive interaction within

both VR systems as well as desktop environments are

proposed and their evaluation is discussed . Section 5

concludes the paper and gives an overview of future

research directions.

2 SEMI-IMMERSIVE VIRTUAL

REALITY SETUP

Since professional urban planners desire to main-

tain intuitive comprehension obtained when viewing

a physical block model, we have chosen a semi-

immersive RWB environment in combination with an

optical tracking system to visualize interactive vir-

tual 3D city models. In comparison to physical block

models, the usage of such a VR system setup enables

an improved interaction with potential building plans,

because interactive modiﬁcation, e.g., texturing and

altering of building parameters, can be incorporated.

The components of the VR system are explained in

the next subsections.

URBAN CITY PLANNING IN SEMI-IMMERSIVE VIRTUAL REALITY SYSTEMS

193

1020mm

left camera

right camera

1000mm

400mm

1360mm

Figure 2: Conceptual view of the semi-immersive RWB.

Two cameras track the area in front of the RWB, where

four users collaborate (adapted from (Dorfm

uller-Ulhaas,

2002)).

2.1 Responsive Workbench

A Barco BARON responsive workbench (RWB)

(Kr

uger et al., 1995), is used to present 3D city mod-

els stereoscopically in a way that enables urban plan-

ners to work in an environment they are accustomed

to. The horizontal or tilted workspace of the RWB

is a well known table-top metaphor many profession-

als are familiar with (see Figure 2). The images are

projected onto the display’s surface so that planners

perceive virtual 3D models as being attached to the

surface (see Figure 3 (right) and Figure 5). This is

due to the fact that the images are rendered stereo-

scopically with negative parallax. The images are dis-

played in sequence and are synchronized with active

shutter glasses the professional urban planners have

to wear. The stereo glasses are transparent, therefore

real-world objects such as the RWB and input devices

can be seen and users are semi-immersed into the vir-

tual world.

The workbench is about 2m × 2m large and 1.2m

high. The display screen measures 1.36m × 1.02m

with a maximum pixel resolution of 1280× 1024. The

maximum refresh rate of 120Hz is ensured with a res-

olution of 1024× 768 pixels, which supports comfort-

able working without ﬂickering effects. As illustrated

in Figure 2 the size and resolution of the workbench

allows several planners to view virtual 3D models

in a stereoscopic projection. City planners can walk

around the RWB in order to view the virtual 3D city

model from different perspectives. To enable such an

exploration from multiple view positions, the system

must be aware of the user’s current position, which

determines the virtual camera’s position and orienta-

tion accordingly. For this purpose tracking systems

are used.

2.2 Tracking System

High accuracy and wireless interaction is indispens-

able for precise and comfortable urban planning,

therefore an optical tracking system is used to deter-

mine the position of the planners as well as their in-

put devices. The accuracy of the stereo-based opti-

cal tracking systems is in the range of submillimeters,

and thus tracking errors are minor and precise interac-

tions with objects displayed on the RWB are possible.

Since lighting conditions around the RWB have to be

darkened because the brightness of the projection it-

self is limited, infrared (IR) light in combination with

IR-ﬁlters is used. The operation area of the track-

ing system is determined by the physical measures of

the workbench, a volume of about 3m × 3m × 1.5m

has to be scanned. To enable an optimal tracking

of this area two cameras are arranged above and be-

side the workbench as depicted in Figure 2. unit Be-

cause of the many drawbacks of IR-LEDs, we have

decided to use passive markers to be tracked by the

system. These markers are made of small spheres

covered with reﬂective material, so that light emitted

by an IR-spot, which is positioned close to the cam-

era lens, is reﬂected back to the camera. Only the re-

ﬂected IR light of the markers passes through a ﬁlter,

which is attached to the front of the lens. With cor-

responding tracking algorithms (Dorfm

uller-Ulhaas,

2002) the position of each marker and thus the po-

sition and orientation of unique rigid body arrange-

ments of such markers can be determined.

2.3 Input Devices

Passive marker tracking provides more ﬂexibility in

comparison to other technologies, e.g., electronic or

magnetic approaches. Attaching certain devices with

a unique rigid body arrangement of at least three

markers results in arbitrary 6 degrees of freedom

(DoF) input devices, i.e., devices whose position and

orientation can be tracked. However, further input

events such as button events and gestures are required

to manipulate a development plan. For this purpose,

we have equipped urban planners with Fakespace

pinch data gloves, which provide a gesture-based

recognition system. Furthermore, we use a hap-

tic input device, which supports planning by vibra-

tion feedback. In combination with acoustic signals

this information can be used to give feedback about

invalid interactions, e.g., collisions between virtual

buildings during the planning process. This device is

equipped with two input buttons, passive markers and

the vibration unit, which enables transmission of hap-

tic signals with different intervals. The buttons can be

used similar to the buttons of a standard mouse, e.g.,

the left button for selection tasks, the right button to

open 3D context menus.

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194

3 3D RESIDENTIAL CITY

PLANNER

The objective of the 3D residential city planning ap-

plication is to provide urban planners an intuitive and

natural interface to plan and modify residential areas

within desktop- and VR-based system environments.

In the following sections the architecture and main

components of this system are introduced.

3.1 Architecture

During the development phase of the application, city

planners express their desire for ﬂexible approaches

for the visualization of generated virtual 3D city

models. Although photorealistic rendering is im-

portant, it is not the only requirement; especially

non-photorealistic rendering supports to comprehend

structures and relations similar to view physical block

models. Furthermore, during exploration interactive

frame rates are more important than photorealistic ap-

pearance. However, realistic visualizations similar to

the renderings provided by architectural ofﬁces are

desired.

Due to these demands, we have chosen VRS,

the Virtual Rendering System (D

ollner and Hinrichs,

2002), as core graphics library for building 3D city

models. VRS is an object-oriented and scenegraph

based C++ graphics library. It introduces the usage of

two different graphs. Geometry graphs, which store

the visual appearance of virtual objects collected in

scene nodes, are combined with behavior graphs to

represent their behavior in terms of interaction and

animation. Different renderings are ensured with this

library, since VRS provides wrapping classes to pho-

torealistic renderers, such as POVRay or Radiance,

but also real-time renderers, e.g., OpenGL, are sup-

ported. Changing the used rendering system without

the need for modiﬁcation of an application’s source

code. Furthermore, VRS is extensible to a VR soft-

ware system by using the Virtual Reality VRS (VR

component (Steinicke et al., 2005a), which handles

all VR related issues.

3.2 Main Components

The 3D residential city planner consists of four con-

ceptual components:

1. Converter tool: The converter tool parses and con-

verts the cadastral data into a scenegraph structure,

which is used to represent the corresponding geo-

data.

2. Geoobject model: The geoobject model is the col-

lection of geoobjects and their properties. This

model is generated during the parser process of

the converter tool. Components of this model are

buildings, building and trafﬁc areas, trees etc.

3. Visualization component: This component con-

structs the scenegraph representing the topological

structure of the city model. Each scene node in the

geometry graph representing a collection of geoob-

jects is associated with a visual appearance, e.g., by

assigning colors or textures.

4. Interaction component: The interaction compo-

nent manages required interactions with virtual 3D

city models. A graphical user interface (GUI)

based on wxWidgets allows to access certain inter-

actions. Alternatively, direct interaction concepts

such as arrangement of virtual buildings are incor-

porated.

The converter tool parses the cadastral data and gen-

erates a scenegraph data structure containing the cor-

responding geodata. Since the cadastral data is geo-

referenced, virtual 3D city models can be gener-

ated automatically. Because there is no overall ac-

cepted standard for storing cadastral information, we

have developed an interface which provides the re-

quired generality and ﬂexibility to enable import of

cadastral data from different sources. For instance,

for the city of M

unster the cadastral data stores

building footprints, number of ﬂoors, parcel bound-

aries and other information in Gauß-Kr

uger coordi-

nates, which are converted during the reconstruction

process. Based on this information the system gen-

erates a geo-referenced virtual 3D city model of the

surrounding area, which is superimposed with aer-

ial photographs to provide more realism and higher

recognition.

Within the geoobject model all geoobjects are ag-

gregated in the class CityModel, which adminis-

trates all required information for a geo-referenced

city model. Instances of type GeoObject provide

the base from which all geoobjects, for example in-

stances of type Building or ParcelArea, inherit.

An instance of the class Building consists of one or

more BuildingParts for handling different types

of stories and roofs. The other geoobjects are orga-

nized analogously.

The visualization component is separated from the

geoobject model of the virtual city. All required

information to visualize the objects of an instance

of the class GeoObject is handled via the class

AppearanceManager. The visual appearance of

each geoobject can be assigned randomly, or the city

planner can deﬁne the appearance, for example by as-

signing speciﬁc textures to each geoobject. As men-

tioned above VRS uses a scenegraph to represent vir-

tual scenes. Since generated virtual 3D city mod-

els may consist of over 50,000 complex, textured

geoobjects, it is not recommend to store each of these

geoobjects in corresponding scene nodes, because

URBAN CITY PLANNING IN SEMI-IMMERSIVE VIRTUAL REALITY SYSTEMS

195

Figure 3: Example photorealistic visualization of a generated 3D city model within the GUI (left) and NPR of the cadastral

data shown in Figure 1 on the workbench (right).

this would inﬂate memory requirements for storing

the scenegraph and decrease performance when eval-

uating it. Due to the wrapping mechanism of VRS it

is possible to store these enormous datasets with ren-

derer speciﬁc optimization strategies.

To assist the city planners during the design process

the graphical representation of both the cadastral plan

as well as the building plan can be projected onto the

virtual 3D city model (see Figure 3 (right)). To further

increase performance, optional view-dependent level-

of-detail algorithms are integrated to enable switching

between different levels of realism. Furthermore, it

is possible to switch between non-photorealistic and

photorealistic rendering.

Besides the standard menu-based interaction con-

cepts, such as creation, arrangement or deletion of

virtual buildings, different navigation and traveling

metaphors can be chosen via menu entries. These ex-

ploration metaphors as well as arrangement of geoob-

jects can be performed in a direct way without us-

ing the menu. These techniques include ﬂying, glid-

ing, walking and ufo-viewing metaphors, i.e., an ex-

ploration with orthogonal view onto the city model.

When exploring a city model, arbitrary locations can

be stored as visual bookmarks to be accessed later on,

for example to generate smooth camera motions along

a resulting path.

When working in desktop-base environments, pro-

fessional city planners have to handle 3D interactions

with 2D input devices, e.g., the standard mouse. To

reduce the cognitive effort for such 3D interactions,

we have integrated 3D widgets (D

ollner and Hinrichs,

1998) into the manipulation process. 3D widgets pro-

vide an easy way to manipulate objects with 6 DoF

by reducing the simultaneously manipulated DoF to

one degree. 3D widgets provide handles for transla-

tion, rotation, and scaling of virtual geoobjects. Thus,

these manipulation tasks can be performed as easily

as in two-dimensions. However, as illustrated in Fig-

ure 5, 3D widgets can also be used in VR.

4 VIRTUAL REALITY

INTERACTION CONCEPTS

As mentioned above VRGIS environments lack intu-

itive interaction concepts. In this section VR-based

interaction metaphors integrated in the 3D residen-

tial city planner are introduced. These generic inter-

action tasks include exploration concepts for collab-

orative interaction in the RWB environment and ad-

vanced manipulation strategies to design, explore and

communicate virtual 3D development plans.

4.1 Collaborative Exploration

When designing a development plan, often several ur-

ban planners with different background, i.e., expertise

and knowledge, are involved. Such cooperations have

been proven to be advantageous since the bundling

of expert’s knowledge has the potential to increase

productivity. Consequently, it is desirable to develop

virtual environments simulating such shared space in

which collaboration can be performed as easily and

naturally as in the real world.

Although the described semi-immersive RWB sys-

tem provides enough space to enable several planners

to interact in a collaborative way, the teamworking

process is constrained due to the shortcoming that

usually only one user is head-tracked and thus per-

ceives a fully perspective-correct stereoscopic image.

Hardware-based solutions to this problem involve re-

duction of the refresh rate (Agrawala et al., 1997).

GRAPP 2006 - COMPUTER GRAPHICS THEORY AND APPLICATIONS

196

Because of physical constraints, these approaches are

hard to scale. Hence, we have developed a software-

based collaboration environment that allows several

city planners to work together in the RWB environ-

ment. The only requirement to enable such a col-

laboration is that each planner who wants to partic-

ipate in the collaboration process has to wear tracked

glasses so that the planners’ head positions can be

determined. Therefore, all input devices and tracked

glasses have to be registered by the tracking system.

If this prerequisite is fulﬁlled, group activity can be

performed by using two different strategies:

1. Cooperative interaction mode, i.e., tasks are ac-

complished consecutively. For example, one city

planner modiﬁes the development plan and after-

wards a second planner continues the work.

2. Split-screen collaboration mode, i.e., users col-

laborate simultaneously. For example, one city

planner creates virtual buildings and provides them

to another planner who arranges them on a building

area.

In both modes active planners, i.e., currently inter-

acting urban planners, perceive a perspective-correct

stereoscopic image either on the entire projection

screen or in different viewports on a tiled screen. Be-

fore any cooperative or collaborative interaction can

be started potential participants need to register. Reg-

istration can be performed by miscellaneous strate-

gies, e.g., posing gestures or using speech commands.

When an urban planner has registered for the coop-

eration and this registration has been accepted, e.g.,

an active planner or administrator conﬁrms the reg-

istration by gestures, this registered planner gets ac-

tive, i.e., his head and input devices are tracked and

used for the interaction. In the case of the cooper-

ative interaction mode, the registered urban planner

switches the state from a passive planner, who only

observes the scene, to the active planner and the pre-

vious active planner gets passive. When a registration

process of an urban planner has been accepted in the

split-screen collaboration mode, the screen is tiled so

that the additional active collaborator is assigned his

own viewport, whereas the viewports of other active

collaborators are scaled down accordingly. Each ac-

tive collaborator perceives perspective-correct stereo-

scopic images in his viewport, therefore interactions

can be performed comfortably.

The introduced concepts allow city planners to

communicate and work together in a very natural

way. A typical planning situation beneﬁting from the

collaborative interaction mode divides the work into

two subprocesses. One urban planner creates virtual

buildings via the GUI by deﬁning building footprints,

heights, roof types and textures etc., while a second

city planner arranges these buildings in the develop-

ment plan. Hence, planning processes can be accel-

Figure 4: Two users collaborating in the a tiled viewport

arrangement.

erated and optimized since several planners can com-

bine their knowledge and abilities. In Figure 4 the 3D

residential city planning software runs in a two-user

split collaboration mode, in which both planners per-

ceive perspective-correct stereoscopic images.

4.2 Manipulation

The concepts described in Section 4.1 enable several

urban planners to explore virtual 3D city models.

The aforementioned typical situation in which two

planners collaborate, e.g., the ﬁrst urban planner

creates virtual buildings, while the second planner

arranges them, involves many problems when using

current manipulation metaphors. While GUI-based

interaction, for instance, generating buildings can

be performed very comfortably in desktop-based

environments or on a personal-interaction-panel in

VR (Szalav

ari and Gervautz, 1997), 6 DoF manipula-

tions of these virtual buildings are often complicated.

Although VR environments provide the possibility

to manipulate virtual objects in an intuitive manner,

e.g., by using a virtual hand or a virtual pointer

(Mine, 1995), these concepts are often constrained,

because in VR the cognitive effort for a city planner is

deﬁnitely higher than the corresponding effort in the

real world. In addition, it is often difﬁcult to perform

precise interactions because of tracking errors and

hand tremors. For example, it is hard to select small

resp. distant objects or items, e.g., the described han-

dles of 3D widgets, with a virtual pointer or virtual

hand in VR. Hence, generic interaction tasks need to

be enhanced. In order to achieve this goal we propose

the improved virtual pointer (IVP) metaphor, which

avoids most of the aforementioned disadvantages

of current interaction metaphors (Steinicke et al.,

2005b). This approach allows the city planner to se-

lect a desired geoobject or item with a virtual pointer

without requiring an exact hit. While a straight ray

is used to indicate the direction of the virtual pointer,

an additionally visualized bendable ray points to

the closest selectable geoobject (see Figure 5). The

URBAN CITY PLANNING IN SEMI-IMMERSIVE VIRTUAL REALITY SYSTEMS

197

Figure 5: Virtual 3D city model and improved virtual

pointer as seen from a city planner’s view.

closest selectable geoobject which would be chosen

if the city planner would perform a selection, e.g.,

by pressing a button or by pinching a glove, is called

active geoobject. Since this geoobject is determined

in a pre-evaluation phase of the scenegraph with

simple geometric calculations, this results in almost

no performance loss. After selecting the active

geoobject, manipulations can be performed similar

to the manipulations of physical block models. The

movements of the virtual input device are transferred

by a scaled one-to-one mapping to the selected

geoobject, which supports also the manipulation of

distant objects. Due to this mapping strategy virtual

geoobjects can be arranged very comfortably and

intuitively.

4.3 Evaluation

In this section the evaluation of the concepts de-

scribed in Section 4.1 and Section 4.2 is discussed.

The subjects chosen for the test series were fa-

miliar with residential planning environments. Most

subjects were geoinformatic students, but also land-

scape ecologists, computer scientists and mathemati-

cians participated in the usability study.

4.3.1 Evaluation of Exploration Concepts

We have tested both proposed cooperative and col-

laborative interaction modes for usability in a pre-

liminary user study with 7 participants. The partic-

ipants were equipped with tracked shutter glasses and

pinch gloves for the registration process. Registration

had to be initiated by simple gestures combined with

acoustic feedback giving an indication which user

wanted to participate in the collaboration and which

user was currently active. Up to three participants had

to explore virtual 3D city models simultaneously by

IVP Sticky-Ray Ray-Casting Sticky-Finger

time in seconds

local distant

(a)

IVP Sticky-Ray Ray-Casting Sticky-Finger

intuitive easy to use easy to learn

(b)

Figure 6: Results of the usability study.

using the described concepts. Afterwards, they were

asked to evaluate the proposed strategies in a user sur-

vey. The results of this survey show that a decreasing

projection size, when splitting the screen into two or

three subviewports, has not disturbed the collabora-

tors in terms of limited space or distraction of other

planners’ viewports. Furthermore, the space in front

of the RWB has been evaluated as large enough for

collaborative interactions. The participants consid-

ered the required gestures for the registration process

as intuitive and easy to learn. Furthermore, the users

evaluated the usage of multimodal feedback, which

supports the users during the interaction, in particular

during the registration process, as very helpful.

4.3.2 Evaluation of Manipulation Concepts

We have evaluated the manipulation concepts in a us-

ability study with 15 participants. During the test se-

ries the subjects had to accomplish several selection

and positioning tasks, i.e., randomly marked virtual

buildings had to be selected and arranged in a devel-

GRAPP 2006 - COMPUTER GRAPHICS THEORY AND APPLICATIONS

198

opment plan by using different interaction metaphors.

These metaphors included the IVP metaphor and a

simpliﬁcation, called sticky-ray metaphor, the ray-

casting technique, and the sticky-ﬁnger technique de-

scribed in (Steinicke et al., 2005b; Bowman and

Hodges, 1997; Pierce et al., 1997). We have eval-

uated the time needed for each subtask and the ac-

curacy achieved with a certain metaphor. The most

signiﬁcant result is illustrated in Figure 6 (a). This

state-chart shows the time needed for a selection sub-

task when using the different metaphors. The results

clearly show that the IVP metaphor improves efﬁ-

ciency and that selections are performed faster for lo-

cal object selection, i.e., selection in the immediate

reach of the user, as well as for distant geoobjects.

Furthermore, performing manipulations was more ac-

curate and precise using the described IVP metaphor.

After the user study the participants have had to

evaluate the metaphors in a ﬁve-point Likert scaled

survey (from 1 to 5 associated with corresponding

ratings). Figure 6 (b) underlines that the participants

have evaluated the IVP metaphor as the most intuitive,

ease to use and easy to learn metaphor in comparison

to the other approaches.

Furthermore, we support the interaction with mul-

timodal feedback. For example, when a selection is

possible, e.g., the selection ray hits a virtual building,

the users perceive a slight vibration and an acoustic

feedback. The intensity of both signals depend on

the position of the virtual building with respect to the

participant’s position. Although in several surveys

participants have evaluated these concepts of mut-

limodality as very helpful, the usage of multimodal

feedback did not increase efﬁciency. However, the

participants felt convenient and conﬁrmed during in-

teraction processes when receiving multimodal feed-

back.

5 CONCLUSION AND FUTURE

DIRECTIONS

We have proposed a 3D residential city planning ap-

plication for semi-immersive VR systems. Due to

the fact that this system has been developed with co-

operation partners from the domain of urban plan-

ning, their demands could be fulﬁlled so that they are

motivated to use the application to develop new build-

ing plans. The user studies have proven the usability

and beneﬁts of the proposed concepts.

Currently, the land surveying and land registry of-

ﬁce evaluate a prerelease version and the urban de-

velopment, city planning and transport planning of-

ﬁce will test the software system in a real planning

process soon. When these ﬁeld studies are ﬁnished,

modiﬁcations of the actual application or integration

of further functions will be accomplished.

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