'Building' ChillTown:

An Independent Study into the Modeling of Virtual Worlds

Lewis C. Hill II


Computer Engineering

Iowa State University

Independent Study Report (Cpr E 490 Section CN, 1 credit)

May 5, 1998

During the spring semester 1998 I pursued an independent study project under the leadership of Dr. Carolina Cruz-Neira, Associate Professor in the Department of Electrical and Computer Engineering, and Associate Director at the Iowa Center for Emerging Manufacturing Technology (Now VRAC). The purpose of this independent study was to learn how to use a modeling package to design a virtual world viewable in the C2 immersive virtual environment. This paper will discuss my experiences in this study and introduce a sample virtual world ChillTown designed during this study.

My experiences in designing virtual worlds has taken on two forms to date. One method involved modeling done strictly with OpenGl(TM) graphics library commands. A different method, used in this study, is to first create a complex world, often referred to as a database, in a modeling package, and then view this world in an immersive environment. Viewing this world usually requires less graphics commands. These commands then handle the details necessary to display the design.

The primary modeling package used in this study is MultiGen II. This software package is developed by MultiGen Inc. It is described as a "Visual Data Base Modeling System." This system allows a user to make a hierarchically organized database of polygons. These polygons have several attributes including color, texture, and material properties. Polygons can also be grouped into nodes. Nodes can be used to represent a sub portion of a complicated geometry. Completed models are saved by MultiGen in the .flt (pronounced "flyte") proprietary format.

Once a model has been created in Mulitgen, it can be displayed and explored in a software package such as Perfly. Perfly is a Performer OpenFlight file loader. Perfomer is a graphics package for perspective rendering (or generating) images of a 3 dimensional database. Within Perfly, users can explore the MultiGen created design. Perfly allows users to set various parameters including lighting sources, level of detail, time of day, etc. to view the effects of various conditions on the database.

The final step in this design study was to view the model in the C2. A discussion of the C2 can be found at http://www.vrac.iastate.edu. The C2 software library facilitates the development applications which load .flt format files, and displays them using Performer for the correct user perspective.

The virtual world designed for this project is entitled ChillTown, an derivative of my user name lchill@yahoo.com. This world consists of an abstract shaped house on top of a large mountain. The house is a multi-layered marble and wood textured structure approximately 40 feet tall. In the center of the house is a semi-transparent 'fishbowl'. This fishbowl demonstrates some of the advanced lighting and material property effects of Performer/MultiGen based applications.

The following are images of the ChillTown environment. Click on them to load larger images.

A distant view of the house on top of the hill.

An overhead perspective

A view near the entrance of the opening.

From the Inside looking toward the opening.

A view of the fishbowl.

Chilltown may be experienced from the ICEMT machines by executing the following commands:
cp ~lchill/caverc_files/caverc_sim_selab ~/.caverc
// This caverc file will specify wand input in simulator mode

~lchill/chilltown/chillnav ~lchill/flts/chilltown.flt

The goal of this project was to learn how to do modeling of virtual environments through a modeling package. Constructing ChillTown has provided an exercise in modeling, color, lighting, and texturing. Loading ChillTown into the C2 system required developing a working knowledge of the Performer rendering package, and the C2 library interface. This project has augmented my personal background in Virtual Reality and will be another tool available for my use in the future.