Me, VANGOGH, and Game Development

Me• Started at UMBC in 2002 (CMSC104)• Undergraduate Research in DIADIC lab (data mining)• Received BS in CMSC, 2006 (Minors in Math and

Philosophy)• Started MS program in 2006 in VANGOGH lab• Multiple TA/RA

– TA for Computer Security (CMSC 426/626), Cryptography (CMSC 443), Computer Graphics (CMSC435)

– RA for high-quality, fast volume rendering (NSF grant)– RA on LINES project

• 2 published graphics papers (3 more in the works)• 2nd year in game development (Firaxis)

VANGOGH

• Graphics lab at UMBC – ITE352• 2 faculty members

– Dr. Rheingans – visualization– Dr. Olano – real-time graphics

• I joined in 2005 – and loving it!

• Join us at our lab meetings:– Wednesday, 10:30am, ITE352

RESEARCH• Undergraduate Thesis “Pre-computed Radiance Transfer

Fur over Arbitrary Surfaces”

• John Kloetzli, Brian Strege, Jonathan Decker, and Marc Olano - “Leveraging Graphics Hardware to Accelerate Dynamic Programming” to be published in EGPGV ’08, EUROGRAPHICS assc.

• John Kloetzli, Marc Olano, Penny Rheingans – “Interactive Volume Isosurface Rendering Using BT Volumes” i3D 2008, ACM SIGGRAPH

MRI Data

MRI Data

Image:

Segami

Corporation

Direct Volume Visualization

Isosurface Volume Visualization

Isosurface Volume Visualization

Introduction

• Isosurface rendering is important in many applications– Medical visualization– Chemistry

• Marching Cubes is the most popular interactive technique– Very fast, BUT– Low quality reconstruction

Marching Cubes rendering

Introduction (cont)

• BT Volumes can do better than MC– Interactive frame rates– Isosurface level changed on

the fly– High-quality reconstruction– Many filters possible

BT Volume rendering

Discrete Volume Data• 3D Scanning devices create a 3D grid of sample

points• Scan: up to about 512 per dimension• Screen: 1600x1200• How do we draw the pixels between samples?

Piecewise Polynomials• We can divide the volume into “cubes”

– Each cube contains a 3D polynomial function– Formula is simple:– How do we determine the weights a?

Piecewise Polynomials (cont)

• We can divide the volume into tetrahedra– Each tetra contains a 3D polynomial function– Formula is fairly simple– How do we determine the weights a?– Huge brute-force minimization problem

Piecewise Polynomials (cont)

• 3D polynomials inside tetrahedra allow us to render isosurfaces very quickly

Contributions

• Our main contribution is an elegant method for finding the weights for each polynomial

• We also presented a real-time rendering algorithm which can display ANY isosurface level

• Our algorithm is robust, automatic, and produces high-quality volume rendering

Comparison

ResultsMolecule (643)

Engine (1283) Bucky ball (323)

Video

Research Questions?

• Part 2: Game Development– A Case Study in Game Development problems

Game Development

• I have always wanted to be a game developer

• Started at Firaxis part-time in summer 2006– Sid Meiers Railroads! –worked on city system– Civilization Revolution

• It really is that much fun!

Railroads!

• Railroad simulator• Player controls

– Laying track– Buying trains– Creating cargo routes between cities/industries– Buy/Sell stock– Buyout opponent

• Typical game development problem: City building placement algorithm

What about Cities?

City Requirements

• Iconic representation of a city– Big buildings in the

middle– Small buildings outside– Different size cities

• Buildings should not self-intersect

• City should not follow “pattern”

City Requirements (2)

• Cities cannot get in the way!

• Player can build track through a city– How should the city

react?

City Requirements (2)

• Cities cannot get in the way!

• Player can build track through a city– How should the city

react?– Our take: City should

“move” around track– How can this be done?

Algorithm

• Create a grid around the city location from a top-down perspective

• Place buildings one at a time• Each building type has a “footprint” which

describes how much space it takes

Small Buildings

Large Buildings

Medium Buildings

Algorithm (cont)

Done

Algorithm (cont)

• Draw the city by randomly choosing a building model from each building type

• This will give basic city shape BUT…– What about terrain? (steep/rivers)– What about the tracks?

• Solution: Before building city, mark grid cells which are “blocked” by terrain or track– Then create the city in the same way

Algorithm (cont)

Water

Track

Results

• Advantages:– Works around all obstacles– Fast enough to re-run per

frame– Maintains city “pyramid”

shape

Results (cont)

• Disadvantages:– Building types can change

when the city is rebuilt– Can be jarring(this can be fixed somewhat

by fixing the number and type of large buildings)

Recommendations

• If you want to do research…– PAY ATTENTION to algorithms!– Don’t be afraid of MATH

• If you want to be a game developer…– Learn C/C++ COMPLETELY– Know how to write low-level code– Know memory management