INTRODUCTION

In addition to GIS, my interests include 3D Graphics and Urban Geography. These two additional interests can be related to each other in the fact that urban environments tend to be rather three-dimensional. Taking these two interests into consideration for my final project I decided to see how 3D output could be produced from a GIS and how it might be applied in an urban setting. My interest in 3D graphics demands output that is, (of course) 3D, animated, and most importantly, interactive. In the area of urban analysis, I came up with the idea of a building height study. Thus my goal for output was a three-dimensional map of urban structures. This map would be interactive and capable of animation.


VIRTUAL MAPS

In brief, a geographic information system is a tool that uses various forms of data as an input to produce a map as an output. Because these maps are easier to understand than raw data, they can be used as a tool to communicate geographic information to a general audience. A map can be defined as an abstraction of reality. Thus map objects symbolize objects in the real world.

Advancement in technology has enabled cartographers to produce maps that are both interactive and animated, similar to most things experienced in reality. More recent developments in hardware and software capability and price have made three-dimensional output extremely affordable. We live in a 3D reality and the purpose of a map is to be an abstraction of reality; so why not output 3D maps that can be both interactive and animated? Why not maintain a 3D-GIS?

Why maintain a 3D-GIS? The conventional 2D maps output by conventional GISs adequately represent functional data, but cannot represent visual data well at all. On the other hand, 3D maps do an excellent job of representing visual data and are also capable of handling functional data. The coupling of 3D-GIS with interactive and animated output can only serve to further a map's ability to accurately depict geographic data.

Current forms of output for 2D maps from GISs are many and include bitmap, pict, gif, and pdf formats. With the recent prominence of the World Wide Web as a medium for information exchange, gif and pdf formats, with cross platform compatibility, are particularly attractive. An attractive format for distributing 3D-GIS output is VRML. VRML 2.0 allows fully imersive environments, interactivity, and real-time animation capabilities. VRML browsers work as plug-ins for common Web browsers and are currently available for most platforms.


CAD and GIS: Graphics meets information allowing for the conception of 3D maps.

An example of photo-realistic rendering used for an infrastructure project (Kinetix).

A current discussion relating to VRML output is the integration of CAD and GIS technologies. This integration is of particular importance to the urban setting with so many structures that are designed in CAD packages. CAD has become critical for modern AEC (Architecture, Engineering, and Construction) projects. CAD has been used for building design, telecommunications facilities layout, and development of highway proposals among other things. The potential for integration of the elements of GIS and CAD for these projects can easily be seen.

While CAD has uses in certain portions of planning, development, and infrastructure projects, it cannot be used by itself to manage them. CAD lacks the networked database that stores and provides access to topological information that is key to a GIS. Additionally, CAD does not have the analysis and modeling tools that are important in considering data such as regional demographics, and traffic flow patterns at precise locations.

On the other hand, standalone GISs cannot sufficiently manage modern infrastructure design and maintenance projects. GISs can meet the informational needs of the projects but lack the graphical capability of CAD packages. GISs represent real world objects as points, lines, or areas.

A suggestion would be to implement a joint CAD/GIS system. CAD tools would be used to create, edit, and maintain graphical information. GIS tools would be used to model and analyze the data related to the graphical information. The marriage seems appropriate since both systems are meant to deal with spatial information. Applications of such a system would include urban design, telecommunications and utilities management, and emergency response services route management. Of particular interest, with regards to VRML, is urban planning and design which would exploit the capability of most CAD packages to model 3D information, especially architectural design (Mahoney 45-46).

Some Obstacles The integration process is not simply a matter of putting CAD tools in the hands of geographers or GIS tools in the hands of engineers. Some problems do exist with the integration of the two technologies. The two types of software packages come from two different traditions. CAD stems from the engineering discipline, while GIS has cartography in its family tree. The Earth is round while most CAD packages perceive it as flat. GIS is used for analysis of large areas, while CAD is being used for solid and Boolean modeling and rendering of relatively small objects. GIS is data driven and must be designed to have a long life as it is continually updated. CAD is project driven and generally used for reference purposes at a later date. GIS concentrates most of its costs in data creation and maintenance (around 80%), while CAD finds most of its costs in hardware and software.

Of course, the most important link between the technologies is people. Important for the integration of CAD and GIS are knowledgeable people who are willing to find a system in which a database containing CAD graphical information, and GIS attribute data can be stored and accessed. Discomfort with data exposure between the CAD and GIS camps must be overcome to achieve higher data quality (Mahoney 48-49).

Reconciliation The most important thing that can be done by the people who are involved in this integration is to adopt standards. Often times, CAD managers don't require a protocol for data entry which is crucial in GIS. To ease integration, CAD drawings must incorporate the following elements:


VRML

There are many visualization software packages on the market that can import CAD files for the purpose of outputting photo-realistic renderings. These renderings can be used for presentation of proposals for new infrastructure and urban development projects. The problem with photo-realistic renderings produced by some of these packages is that they can be used to portray the proposals in ways that may be "unrealistic." That is, 3D software package cameras can do everything that real world cameras can do and more. These renderings can be used to make good things look bad and bad things look good. These software packages can place lights and cameras

An example of visualization software using artificial light colors to alter the appearance of a building (Kinetix).

in dramatic positions that we would never actually experience in real life. The bottom line is that these renderings can be done to either support or counter the proposal based on the stance taken by the artist or those paying him/her.

With the use of 3D data in the form of CAD files and high quality texture maps, many 3D graphics software packages can export fairly realistic VRML files. VRML files, while not as realistic as photo-quality rendered still shots and animation, hold many advantages. VRML browsers allow observation of the project from just about any imaginable location or angle. Information regarding the positioning of lights and cameras in VRML files are readily available in the source code. This information can be checked by the viewer to assure that the representation of the project is not over-dramatic or otherwise unrealistic. VRML is both neutral and interactive.

With regards to capabilities, VRML holds other advantages over the photo-realistic output of high-end 3D graphics packages. New, with VRML 2.0, is an elevation grid node that is of special interest to geographers in that it can be used to represent geographic terrain data. VRML allows the linking of three-dimensional objects to data or other objects. The interaction allowed by VRML is far greater than that offered by a still rendering. Aside from interactively positioning point of view, VRML allows the user to interact with 3D objects in a 3D world. This feature, along with the linking feature would be useful for querying objects on a 3D map about attribute data. Photo-realistic animations can take hours, or even days, to render depending on resolution. Animation in VRML is rendered in real-time as the user moves through the scene. VRML 2.0 also allows the author to script animation so that predefined walk/fly-thrus can be awaiting the viewer upon entry into the 3D map. The best part is that high-quality VRML browsers are publicly available for free and work with high-quality web browsers that are also publicly available for free.

The bottom line is that VRML allows a virtually bias free way to examine visual-spatial data in a form that can easily be ported to the public. Thus, VRML may be a good tool for implementation of social GIS.


EXERCISE

Theoretical Scenario A small city currently has a local zoning ordinance that restricts the all buildings to being no more than three stories high. At the time that this ordinance was implemented, the local fire department was not equipped with a ladder truck that would be adequate for taller buildings. The fire department has subsequently obtained new equipment including a ladder truck that is capable of six story rescues. Pointing to this fact, a local developer, wishing to construct a four-story apartment complex, makes an appeal to the city planning commission. A 2D GIS is easily capable of pointing out that the site is indeed within the district of the properly equipped fire department.

Residents of the city object to the proposed building, siting that the apartments will cause increased traffic, overshadow the local neighborhood, and additionally not conform to the traditional, historic neighborhood. An architect's still rendering of the proposed building can display that the architecture of the structure would in fact conform to the local neighborhood style. A conventional 2D GIS showed that local streets in combination with the proposed building's access would handle the minor traffic increase caused by the 24-unit luxury apartment building. As the included land use and general maps show, the proposed site is currently occupied by several vacant lots, a couple of parking lots, a single-family house and a small commercial/residential mixed-use building that is mostly unoccupied.

While the architect's still renderings sufficiently accommodated local questions of conformity, they did not address concerns of overshadowing of the surrounding buildings. This is where VRML output from a 3D-GIS is used.

Note: This exercise does not use an actual study. Instead, it uses a theoretical scenario to emphasize the general capabilities and possible applications of such technology in the production of interactive three-dimensional maps. In practice, maps would be generated from a true GIS and use actual CAD models for the representation of the buildings.

Making an Interactive 3D Map I started by this exercise by generating two-dimensional base maps in Adobe Illustrator. Following the layering convention outlined above, I had separate layers for structures, land use, block outlines, property divisions, parking lots & sidewalks, green space, and streets. My data was accurate (or more correctly for a theoretical scenario, precise) to well within a foot.

To give the viewer a general sense of the setting, I started by producing six map layouts for the proposal. A general map and a land use map were produced in Illustrator for the project for both the current state of the site and the proposed state of the site with new four story building. In addition to these four maps, two maps were produced showing relative heights of the buildings. With these maps the user could get a general feel for the area, but not a true sense of the atmosphere created by the different building heights.

At this point I made a layer for each class of building height and saved each as an Adobe Illustrator (*.ai) file. Next, I opened an empty scene in MetaCreations Ray Dream Studio. Using the extrusion tool in Ray Dream, I extruded each building height layer to an appropriate length to represent the different building heights. Next, all of the layers we're checked for alignment to assure proper geographic representation within the scene. Once the scene was properly aligned and colored to match the base map, I exported the scene to a VRML (*.wrl) file. My basemaps for extrusion were similar to the height maps available below.

 In the VRML source code, I added a hyperlink to each building layer to give information when the building was queried. In an actual project each building would probably have its own information, but for the purpose of showing the capability of this form of output a single set of data suffices for each height layer. By examining the 3D map, the planning commision and citizens at large would be able to examine an unbiased 3D representation of the site and cast more informed opinions regarding their concerns about proposed developments.

I feel that with this exercise, I achieved my goal of producing an interactive 3D map that shows the possibilities of output from a 3D-GIS.

Note: These maps are designed to be viewed at a minimum color setting of 256-colors and at a minimum display area of 800 x 600 pixels. Viewing of the 3D maps requires a plug-in VRML browser such as Cosmo Player, which works with Netscape Navigator 3.X & 4.X and Internet Explorer 4.X.

The Maps:


Work Cited:

Mahoney, Diana Phillips. "Merging CAD and GIS." Computer Graphics World. March 1998: 45-50.

Kinetix, Autodesk. A desktop 3D graphics software company that makes an AEC visualization package called 3D Studio VIZ.

 

Other Works:

Hartman, Jed and Wernecke, Josie. The VRML 2.0 Handbook. (Silicon Graphics, Inc., 1997)

Jacobson, Robert. "Virtual Worlds Capture Spatial Reality." GIS World. December 1994: 36-39.

 

Links:

Cosmo Software, Silicon Graphics Inc. A software company specializing in Java and VRML authoring tools. Free Cosmo Player VRML Browsers are available at this site.

The VRML 2.0 Handbook developers Web site. This site contains some interesting 3D worlds that are examined in the handbook.

Lightscape Technologies. A software company that specializes in a special form of photo-realistic rendering known as radiosity. This site contains some nice VRML worlds produced using this sofware.

Architektur. German 3D GIS. A joint study between two German Universities to apply virtual reality output to urban planning.

GeoVRML Working Group is a discussion forum for addressing the issues of representing geo-referenced data in VRML.

Ocnus' Rope Company maintains a Java and VRML page.


Submitted by Scott A. Carson on May 1, 1998