Development of the VR-CAD System
for Landscape and Town Planning
Koji Makanae
School of Project Design, Miyagi University
1 Gakuen, Taiwa-cho, Kurokawa-gun,Miyagi 981-3298, Japan022-377-8368
koji@makalab.org

ABSTRACT
A virtual reality computer-aided design (VR-CAD) system that provides a virtual
space was developed. The system uses a head mount display (HMD) to create a virtual
space and reproduces topographic features from digital terrain information. A 3D
positioning system is used to model highways, buildings, and trees in the VRenvironment. The modeling experiment by architects suggests only usefulness of 3Dmodeling, but also problems about the sense of scale, recognition of the cursor, anddifficulty of highway modeling.

KEYWORDS
Virtual Reality, Head Mount Display, Town Planning, Landscape Design

INTRODUCTION
Civil engineering structures are three dimensional (3D), although two dimensional(2D) approaches based on drawings are conventionally used in the design of such
structures. The knowledge of 3D geometries of topographic features is indispensable
because they function as structural foundations. The designers are required to have theability to convert 2D terrain data to 3D data in their mind. This ability, which greatly
depends on the experience and the skill of each designer, affects the quality and theefficiency of designing structures of complicated shape or structures built oncomplicated terrains.
To address this problem, virtual reality technology is used in this study to develop avirtual reality computer-aided design (VR-CAD) system for landscape and town
planning. A head mount display (HMD) is used in the system to reproduce a 3D
digital terrain model (DTM), on which design work can be carried out.
Concept of the VR-CAD system
Virtual reality is a technology to create simulated worlds by use of computers.
Virtual reality can be applied to many areas including design, simulation studies,games, and education to add realism.

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Fig.1 The concept of the VR-CAD
The present virtual reality technology can provides humans with computersynthesized information associated with not only visual but also auditory and tactile
senses to create virtual worlds.
Tools typically used to create virtual spaces include HMDs, data gloves, motion
capture systems, CAVE systems (Cruz-Neira et al., 1993), and 3D positioning systems.
As an example of 3D modeling system, “3DM” developed by Butterworth etal.,(1992) is a 3D modeler utilizing a HMD. Kwaw and Gorny(1999) developed theVirtual-CAD(VCAD) that supports design of virtual technical object in a threedimensional stereoscopic environment using pre-defined virtual construction elements.
Tanaka et al.(2000) presented a cutting-operation simulation system, which employs astereoscopic system and a force-feedback pointing system (PHANToM) to simulatethe cutting operations of 3D polygon models. Hashimoto and Nakajima (1999) aredeveloping a modeling system that works in an immersive display system CAVE.
Also, a modeling system called Illuminating Clay, which allows synthesis of flexible
clay models and 3D computer images, is being developed at the Department of Urban
Studies and Planning of Massachusetts Institute of Technology (Piper, et al., 2002).
Against these works, this paper aims to develop the VR system for infrastructure
and landscape design with the terrain model. Conventionally, civil engineering
structures are planned and designed on drawings, which are drawn by designers whoconstruct 3D geometries in their mind. By using virtual reality technology, 3D virtual
spaces can be defined arbitrarily on a computer. The authors have developed ahighway design system that is based on the stereoscopy of aerial photographs(Makanae and Fukuda, 1998; Makanae, 2002). This is a type of VR-CAD that allows
3D highway route planning using parametric curves in the stereoscopic environment
given by a pair of aerial photographs. When aerial photographs are used, however, thedesigner's view is restricted by the photographing point in the air, and it is difficult torelate the processing of design structures directly with topography.
This study provides a system in which highways and other facilities are designed
based on a 3D terrain model constructed from digital terrain data for landscape andtown-planning. As schematically shown in Fig.1, the VR-CAD system developed inthis study allows a designer as a giant to get into a virtual space created on thecomputer and move freely over the space for design operations.
The system requirements for the VR-CAD are below;- Build the VR environment in which a designer can move freely as a giant.
- Represent the terrain model in the VR environment.
- Model and place the objects such as building, trees, and highway.
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VPL EyePhone90

ball-type motion
sensormotion sensor

RS232C

Polhemuselectromagnetic motion sensor system
IsoTrak IItransmittergraphic workstation(IBM Intellistation)

Fig.2 Hardware components of the VR-CAD

Hardware configuration
The hardware configuration of the VR-CAD system developed in this study isshown in Fig.2.
Image processing systemThe image processing system is built around an IBM Intellistation ZPro with anIntel's 550-MHz Pentium III Xeon CPU, 256-MB RAM, and 9-GB disc space. A dualmonitor graphics board (Millennium G400) is used for the simultaneous output of twoimages on a HMD.
3D positioning system
As a virtual reality input device, a 3D magnetic positioning system (Polhemus
3SPACE ISOTRAK II) is used to track user's movement. This system acquires
positional data without contact by use of magnetic transducing technology.
Two magnetic sensors are used in the system.
(a) Head tracking sensor
A magnetic sensor is attached to and interlocked with the HMD. The sensor detects
the position and the direction of the user's head and outputs X, Y, and Z, coordinatesand Euler angles (pitch, yaw, roll). The standard sensor is attached to the head tocontrol the view point of the user in the virtual space.
(b) 3D mouse sensor (ball type)A ball-type magnetic sensor is used as a 3D mouse. The on/off data of the switcheson the sensor can be acquired.
HMD (VPL Research Eyephone90)
The HMD has two liquid crystal displays (LCDs) with a resolution of 640 x 480
pixels to cover the views of the user's right and left eyes. Different images can beshown for the right and left eyes. Stereoscopic vision is given to the user by displaying
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images of different view points on the two LCDs in consideration of the parallax ofboth eyes.
With the combination of the HMD and the magnetic sensors, the position and thedirection of the head are measured and corresponding images are displayed so that theuser can view all angles in both horizontal and vertical planes.
Development of the VR-CAD system
The VR-CAD system was developed by using Microsoft Visual C++ 6.0 and theOpenGL graphics library. The basic flow of the system is shown in Fig.3.
Build the VR environment
The sensor part of the 3D positioning system is attached to the HMD so as to track
positional data according to head movement. The positional data is analyzed by thecomputer, and appropriate images for both eyes are created according to the view
point and the viewing direction. Images are renewed at 0.15-s intervals. Images areoutput on the HMD to provide stereoscopic vision to the user based on the parallax ofboth eyes.
Represent the terrain model in the VR environment
During the system startup, 50-m-mesh altitude data issued by the Geographical
Survey Institute of the Ministry of Land, Infrastructure and Transport (JAPAN) is readstartacquirethe HMD position data
render the scene

HMD

acquire the3D mouse position andCommands
build the 3Dmodels

YESNo

Makea model?
Noquit?
YES
endFig.3 A flowchart of the modeling system

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highwayIHGFtreeCAdragdragEB

building

DbuildingFig.4 Modeling objects
to construct a 3D terrain model. The user conducts modeling operations based on thismodel.
Model and place the objects
The system allows creation of simple 3D models such as buildings, trees, andhighways (viaducts) on the terrain model. through the numeric keyboard and the 3Dmouse.
(1) Buildings
Buildings are simply shaped, either rectangular solids or cylinders. A rectangularbuilding can be given by two diagonally opposite points, and a cylindrical building iscreated by calculating a center point, radius, and height from two given points.
(2) Trees
Trees in the system are created as joint models, which are used for expressing
humans, animals, plants, and other objects in computer graphics. A simple 3D treemodel can be created by defining a tree structure.
(3) Highways
With regard to the creation of highway models in 3D spaces, Makanae(2000)
discussed the applicability of spline, Bezier, and B-spline curves, and the cubic Bspline curve which makes for the smoothest transition for roads is most applicative forhighway alignment. In this study, cubic B-spline curves are adopted in this study tocreate 3D highway models.
In the present system, control points can be defined in a virtual space by using the3D mouse, and the center line of a highway is defined by a B-spline curve given by
the control points(ex. Fig.4, F, G, H, I). A 3D highway model is created based on thehighway line and predetermined cross-sectional data. The system does not take thecross-fall of the highway into account.
Modeling operation
A view of modeling operation using the VR-CAD system is presented in Fig. 5.
Topographic data is delivered as 3D information to the designer through the HMD.
To generate images, the location and the direction of the designer's head are detectedby the sensor attached to the HMD. After selecting a kind of object type through anumeric keyboard, then a user models an object by moving a 3D cursor(grey-coloredball) in the VR environment.
-building: drag the cursor between two diagonally opposite points(Fig.4 A-B, C-D)
-tree: click on the point to plant a tree(Fig4 E)
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Fig.5 A scene of modelingFig.6 Stereoscopic images by the VR-CAD-highway: set the control points.(Fig4, F,G,H,I), then command to make 3D models
through a numeric keyboard
These objects are attached to the ground automatically.
An example of modeling is shown in Fig.6. The two images are for the right andleft eyes.
Evaluation of the VR-CAD
To make clear the effectiveness of the VR-CAD in this study, an experiment iscarried out. The experiment is to model the objects (buildings, highways, trees) freely
in the virtual environment. Subjects for the experiment are 5 architects who haveexperiment using the 3D-CAD. After modeling the objects, subjects evaluate spatialrecognition and usability in 5 grades. Average values of the each item of evaluation
are shown in Table.1.
According the result, stereognostic sense and recognition of the terrain feature havebetter grades, but sense of scale, the recognition of position of a cursor and positional
relations between the terrain and objects are problems about spatial recognition.
Regarding modeling usability, building and tree modeling have better grades, but
highway modeling is evaluated as difficult. As other problems, some subjects pointout a need for much time to training to use the system, tiresomeness to walk around in
the VR environment while designing. As merits of the VR-CAD, ease of 3D modelingand acquisition of 3D view, usefulness for landscape design are pointed out by somesubjects.

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Table 1. Evaluation of VR-CAD
Category
Sense and Recognition

Modeling Usability

Item
Scale
Stereognostic sense
Terrain feature
Position of cursor
Positional relation between
the terrain and objects
BuildingTreeHighway

Average (1-5)
2.4
3.8
3.4
1.8
2.6
3.6
3.6
2.8

Conclusion
A VR-CAD system using a HMD was developed and its effectiveness for landscapeand town planning was discussed in this study. Civil engineering structures such as
highways can be designed in a virtual space define on a computer. The modelingexperiment by architects suggests only usefulness of 3D modeling, but also someproblems about the sense of scale, recognition of the cursor, and difficulty of highway
modeling. To solve these problems, improvements of user interface are required.
The capability of the developed system is limited to constructing terrain models andmodeling and placing simple buildings, trees, and highways. To put the system topractical use, the software needs to have advanced functions such as processing in
relation to topography. In the conventional method, 2D drawings are used for 3D
design. However, the concept of drawing does not exist in the 3D virtual space createdby the VR-CAD system. 3D design methods need to be established regarding how tocarry out design work and how to define information in the 3D virtual environment.
References
Butterworth, J., Davidson, A., Hench, S and Olano, T.M.(1992): “3DM: A three
dimensional modeler using a head-mounted display”, Proceedings of ACM
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Cruz-Neira, C., Sandin, D.J., Defanti, T.A.(1993): Surround-Screen Projection-Based
Virtual Reality: The Design and Implementation of the CAVE, Proceedings ofSIGGRAPH’93, pp.135-142.
Kwaw, E.K.A. and Gorny, P.(1999): Reality in Virtual Construction Using VirtualCAD(VCAD), Proceedings of the Eighth International Conference(ICCCBEVIII),ASCE, pp.317-324.
Hashimoto, N. and Nakajima, M.(1999): 3-D Modeler based on Intuitive Operations
and Dynamic D.O.F. Controls in CAVE, Transaction of the Virtual Reality Societyof Japan, 4-3, 487-494.
Makanae, K. and Fukuda, T.(1998): "Highway Alignment Planning System Utilizing
Stereo-viewing of Aerial Photographs and Computer Graphics.", Journal of
Infrastructure Planning and Management, JSCE, No.590/IV-39, pp.23-30.
Makanae, K.(2000): "An application of Parametric Curves to Highway Alignment",,
Journal of Civil Engineering Information Processing System in 1999, 231-238.

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Makanae, K.(2002): Stereoscopic Systems for 3-D Highway Route Planning on Aerial
Photo-graphs, International Journal of Design Sciences & Technology, Europia
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Piper, B., Ratti, C. and Ishii, H.(2002): Illuminating Clay: A 3-D Tangible Interface
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Tanaka, A., Hirota, K. and Kaneko, T.(2000): Deforming and Cutting Operation withForce Sensation, Journal of Robotics and Mechatronics，Vol.12，No.3，pp.292303.

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