Programming assignment #3 - 3D Video Game
CS 248 - Introduction to Computer Graphics
Autumn Quarter, 2001
Game proposals due Tuesday, November 13 by 2:00pm
First demos on Monday, November 19
Final demos on Wednesday, December 5
Writeups due on Friday, December 7 by 5:00pm
Your assignment is to write a 3D video game using OpenGL. You are free to
design and implement any sort of game you like, as long as it incorporates the
required functionality described below. For purposes of this project, we
consider a 3D video game to be an interactive 3D computer graphics application
that has a challenging goal, is fun to play, and incorporates some concept of
scoring or winning and losing. It is not required that your game idea be
original, but originality will be rewarded with extra credit. If you have any
questions about whether your idea meets the criteria for a 3D video game,
please ask the course professor or a TA. Your game proposal (due November 13),
and our feedback to you afterwards, should help you in developing your game
You are permitted (and encouraged) to form teams of 2-3 people and partition
the work among the team members. The work expected from each team will be
proportional to the size of the team. You can use the class newsgroup
su.class.cs248 to find prospective team members.
Each team should submit a single game proposal, jointly authored by all team
members. You may change the composition of your team at any time prior to
November 28 (one week before final demos). However, changes after the first
demos (on November 19) are strongly discouraged.
Within the overall framework of your video game, you are required to include
the following functionality:
- 3D viewing and objects.
Your game environment must be a scene consisting primarily of 3D elements, as
opposed to only "flat," 2D sprite-based graphics. Your game should provide
perspective views of your 3D scene where at least sometimes the viewpoint
changes smoothly under some combination of user and program control. To
produce these views, you should implement transformation, clipping, and
hidden-surface removal of your 3D scene using OpenGL.
- User input. Your game must allow players to interact with
the game via keyboard or mouse controls. Alternatively, you can use joysticks
or more elaborate user interface devices (provided that you supply the required
devices for your program demonstration sessions; see below).
- Lighting and smooth shading.
Your game must contain at least some objects that are "lit" using OpenGL's
lighting model. For these objects, you'll need to define normal vectors and
materials, as well as create one or more light sources. See Chapter 5 of the
OpenGL Programming Guide for details on implementing lighting and
- Texture mapping.
You must implement texture mapping for at least one of the 3D objects in your
video game. Chapter 9 of the OpenGL Programming Guide describes how
to implement a variety of texturing techniques. If you want, you can use your
paint program from assignment #1 to create 2D texture maps in the .ppm
image format, and/or borrow the xsupport source code from assignment
#1 to load .ppm files into your game for use as textures.
In addition to these basic requirements, your game should incorporate some of
the more advanced computer graphics techniques listed below, depending on the
size of your project team. In particular, you are required to implement at
least 2*N of these additional techniques, where N is the
number of people on your team (i.e. groups of three people need to implement
six techniques, individuals working alone are required to implement only two,
etc.). Of course, you are encouraged to implement as many of these techniques
as you can, depending on the requirements of your particular game engine, as
well as using any other ideas you read about or invent on your own. Extra
effort will be rewarded with extra credit.
- On-screen control panel. Many 3D video games reserve
part of the display area for an on-screen control panel, which may include text
or 2D graphical elements for user controls, scoreboards, etc. Flight simulator
games often superimpose 2D graphical overlays on the 3D world, thereby creating
a "Heads Up Display (HUD)." You can implement a control panel for your game
using a variety of techniques in OpenGL, such as orthographic projection and
the stencil buffer. Text primitives are not explicitly supported with OpenGL,
but GLUT and the window system extensions (GLX, WGL, etc.) both provide
commands to help render text.
- View frustum culling. In video games with complex
3D environments, it is necessary to limit the number of 3D primitives drawn
each frame in order to maintain interactive rendering rates. One way to do
this is to avoid drawing any 3D objects which are outside of the viewing
frustum of the camera. A more sophisticated technique is to pre-compute
bounding volumes for objects and then test each bounding volume to verify that
some part of it intersects the view frustum before drawing its contained
objects each frame. Finally, for even greater efficiency, you can organize
your objects (and bounding volumes) into a tree-like data structure, sometimes
called a hierarchical scene graph. Object hierarchies are discussed
in Chapter 7 of the textbook. and view frustum culling is discussed in Section
7.1.2 of Möller and Haines's book, Real-Time Rendering.
- Level of detail control. Another way to limit the number
of 3D primitives drawn each frame is to implement level of detail (LOD) control
in your game. One simple method of LOD control involves creating multiple
versions of some of your 3D objects, varying in geometric complexity (such as
10, 100, and 1000 polygons). Then, before drawing the objects each frame, you
can pick the most appropriate version of the object to render, depending on
such metrics as the distance of the object from the viewer, the complexity of
the current scene, or a user-selectable detail level. Levels of detail
are discussed in section 7.3 of Real-Time Rendering.
- Occlusion culling. Yet another way to maintain good game
performance with complex environments is by performing occlusion culling.
Similar to view frustum culling, this technique involves using a conservative
computation to avoid drawing any parts of the 3D scene which won't be seen by
the viewer because they are hidden behind other objects. For static
environments such as buildings, you might pre-compute which regions of space
(such as rooms) are impossible to see from other regions (due to occluding
walls, for example). More information on occlusion culling is in sections
7.1.3 and 7.1.5 of Real-Time Rendering. (Don't confuse occlusion
culling with simple hidden-surface removal, which is required for your video
- Procedural and physically-based modeling. In addition to using
scanned or hand-modeled objects to populate the 3D worlds, some video games use
procedurally computed models. Chapter 20 of the textbook describes examples of
procedural modeling, including fractally-generated mountainous terrains and
L-grammars for generating models of plants. Procedurally generated textures
may be used to simulate effects such as fire, smoke, and clouds.
- Collision detection. Video games often contain moving objects
which trigger events when they collide, such as projectiles shot at a target.
Collision detection can also be used to prevent the user from passing through
walls or other objects. You can implement collision detection in a variety of
ways; the simplest might involve comparing bounding volumes of objects to
decide if they intersect or not. If you have complicated objects, a
hierarchical scene graph (see view frustum culling above) may prove helpful to
accelerate your collision detection tests. Chapter 11 of Real-Time
Rendering describes a number of collision detection techniques.
- Simulated dynamics. Your video game implementation might include
modeling dynamic behaviors and physics for objects in the 3D world. For
example, the wheels of a vehicle might react realistically as they move over
rough terrain, or a ball might bounce differently depending on its velocity,
elasticity, and the characteristics of the surfaces it hits. Realistically
animated characters in 3D graphics applications are sometimes controlled
via simulated dynamics.
- Motion capture animation. Motion capture data is
used with many modern 3D video games to allow characters to
move realistically. Pointers to some motion capture data files
and implementation ideas are on the assignment resource web page.
- Advanced rendering effects. OpenGL makes it possible to
easily implement a wide variety of realistic rendering effects. Some
of these effects can be achieved by drawing the scene multiple times
for each frame and varying one or more parameters each pass through the
scene; these techniques are called "multi-pass rendering." Other
techniques combine traditional 3D graphics rendering with 2D image-based
graphics. Advanced rendering effects you can add to your video game
include soft shadows, reflections, motion blur, depth of field,
bump mapping, environment mapping, billboarding, and projective texturing.
See chapter 6 of Real-Time Rendering as well as the pointers on the
assignment web page for examples and information on implementing advanced
multi-pass and image-based rendering techniques.
- Sound. Adding appropriate audio effects to your game can provide a
more compelling experience for the player. The details of sound effect
creation and implementation of audio playback in your game engine will depend
on your hardware configuration; some pointers to relevant documentation and
sample sound effects are included on the assignment web page.
- AI. Some video games include computer-controlled agents that
require a significant degree of artificial intelligence. Many of the
techniques taught in a basic AI course are applicable to video game
development, and some links to more detailed information on game AI are
included on the course web page for the assignment. If you have any doubts
about whether a technique you are using qualifies as "AI" for this assignment,
- Networked multi-player capability. Networked multi-player video
games allow more than one player to play at once, either collaboratively or in
competition, using computer networks such as the Internet. If you add
multi-player capability to your video game, you'll need to deal with issues
such as network latency by using predictive techniques. Some pointers to basic
information on implementing networking in games will be provided on the
assignment web page.
- Game level editor. Some video games are accompanied with
supplementary computer graphics applications which allow users to design their
own game levels (scenes). If you develop your own custom application to
construct levels while writing your game, you might consider packaging it as a
separate utility program for end-users to enjoy as well!
A few hints
- This project is purposefully designed to be more open-ended than
the first two assignments of the course. You will be expected to do a
considerable amount of learning on your own, particularly in gaining experience
with programming in OpenGL. We will cover the high-level concepts of OpenGL in
class, and we have assigned some sections of the OpenGL Programming
Guide as reading. There will also be an OpenGL help session on Friday,
November 9, at 3:15 in Gates B03. Beyond this, please take advantage of the
opportunity to consult the course professor and TAs with questions concerning
development of your particular video game. If there are computer graphics
techniques not covered in the course that you would like to implement, we will
usually be able to point you to an appropriate source of information. In order
to assist and inspire you, a web page is available at the URL:
This page includes pointers to OpenGL tutorials, information on game
development, useful utility programs, and sources for 3D models and other game
content. Additional examples of OpenGL code from the programming guide and
OpenGL and GLUT distributions are available in the class directory in
/usr/class/cs248/assignment3. Of course, you are responsible for
understanding and implementing your own video game code; sharing code or
libraries between teams is not permitted. Using source code, libraries, or
executables you find on the Internet (or elsewhere) is permitted, but is
limited to programming tools and low-level utilities. In particular, borrowing
the code that implements basic or advanced game features (as enumerated above)
is not allowed. Looking on the Internet for ideas, even looking at
sample code you find there, is permitted and encouraged. However, when you do
this, we expect you to cite your sources in your writeup.
- Interactive 3D graphics programs such as video games
place special demands on computer hardware. If your 3D world is particularly
large or complex, or if you use certain OpenGL rendering features (such as
texture mapping), you will probably need special graphics hardware in order to
get real-time performance. Note that some of the Sun systems in Sweet Hall
do not implement texture mapping in graphics hardware, so games making
intensive use of texturing will suffer performance limitations on these
systems. The firebird and raptor systems are equipped with NVIDIA graphics
cards, which deliver excellent 3D graphics performance. If you develop
your game onanother platform, it will probably be useful to add options to
optionally disable expensive features (such as texturing). The performance
of your video game is important, so do not implement too many expensive
rendering features if the gameplay is negatively impacted! There are some
pointers on the assignment web page to sources of information on maximizing
- Most successful video games include richly detailed 3D models, textures,
sounds, and other content for representing the game world and characters.
You have several options available in creating the content for your video game:
- Simple models can be sketched on graph paper, and the coordinates
manually typed into your source code.
- Models can be procedurally generated, as mentioned above.
- You can use a 3D modeling package and export the model in
a format your program can read.
The assignment web page will contain pointers to several freely
available modeling packages.
- The GLUT library provides functions for drawing simple
3D shapes (sphere, cube, etc.)
- You can find a wide variety of 3D models, textures, and sounds
on the web; see the pointers on the assignment web page. These may
need to be converted to a format your program can use; we will provide some
example source code for loading models.
- OpenGL is window system independent, so an additional toolkit is necessary
to provide the necessary windowing and input event management; for this we
recommend using the GLUT package. GLUT is used for all the examples in recent
editions of the OpenGL Programming Guide, and is available for most
all common computing platforms. A simple example program and Makefile using
OpenGL and GLUT on the Sweet Hall graphics lab PCs is available in
/usr/class/cs248/assignment3/example. GLUT offers a very limited set
of user interface widgets (little more than menus). If you require slightly
more extensive user interface functionality, consider trying the
MUI, PUI, or GLUI toolkits; they are easy to use, and are written entirely
on top of GLUT and OpenGL. You may recall GLUI was used for assignment 2.
Documentation is available on the web (see the assignment web page
for pointers). You are free to use other user interface toolkits of your
- You are also free to develop your video game on any computer platform that
supports OpenGL, provided that you will be able to demonstrate your program at
the two required demonstration periods at Sweet Hall. If your program cannot
run on the Sweet Hall graphics lab PCs, you will be responsible for bringing a
system to those labs on which to run your video game. Versions of OpenGL for
most common computing platforms are available for download at sites pointed at
from the assignment web page.
- In the course of designing and implementing your video game,
keep in mind that CS248 is a computer graphics course. Focus your efforts on
the computer graphics techniques underlying the game; don't spend the majority
of your time on game design or object modeling if the graphics engine will
suffer as a result! Finally, don't make your 3D world or game engine so
complicated that interactivity suffers. Your game must be playable!
We'll be grading your advanced techniques on a bucket system: minus,
check-minus, check, check-plus, plus. Your grade on this scale will depend on
the difficulty of what was implemented. Stated simply, grades will be
proportional to effort. To get an A on this assignment, we need to see
outstanding effort on at least one advanced feature. In general, although
implementing more features will increase your grade, we prefer that you
implement fewer features but do them well, and we will grade accordingly.
Video game submission requirements
The game proposal.
Your first milestone is a proposal, due by 2:00pm on Tuesday, November 13.
Your proposal can be brief - 1 page is plenty. Be sure to list all team
members. The proposal should clearly state the premise of your game, describe
the 3D world you plan to build for it, outline the gameplay, and enumerate the
2*N advanced techniques you plan to implement. If you envision
facing any special technical challenges (like predicting collisions between a
basketball and a hoop), list them. If you envision implementing any special
bells and whistles (like the ability to play against 5,000 networked opponents
simultaneously), list those too.
Submit your proposal by emailing it to
email@example.com. Submitting a proposal is required,
and late submissions will be penalized, but your proposal will not be graded.
Neither will you be held to either the list of advanced graphics techniques you
enumerate or to the composition of your team. The purpose of this proposal is
to motivate you to begin working on the project, and to give us a chance to
guide you. We will read and respond (by email) to every proposal. Hopefully,
most of these responses will be of the form, "Cool game idea! Full speed
ahead!". However, if we see you headed towards the shoals, we'll let you know.
On Monday, November 19 you will demonstrate your partially complete video game
to a member of the CS248 course staff.
To show reasonable progress,
your 3D world should be largely in place, although perhaps lacking in detail or
performance, your "gameplay" should be basically working, and at least some of
the required graphics functionality (3D viewing, user input, lighting, and
texture mapping) should be implemented. The 2*N advanced techniques
need not be in place, except that depending on your game, you might need to
have already implemented some of them in order to demonstrate your gameplay.
At the demo, we will give you feedback on your game, and we will discuss with
you your plans for finishing it.
Signups for these demos will be handled electronically, as usual. You can demo
on any platform you like, even a laptop. However, all demos must be given in
the Sweet Hall basement graphics labs. There is no need to freeze your code
before the demos. All team members must be present at the demo. Late demos
will be permitted, but will be penalized in the usual way. No writeup or
submission of source code or other files is required following these demos. In
addition to giving you verbal feedback at the demo, we will also grade you.
Since you are not submitting code, these grades will based only on what we see
during the demo. However, these grades will be simple: minus, check-minus,
check, check-plus, plus, depending on the quality of your progress.
Final demos and writeups.
Your complete video game will be demonstrated on Wednesday, December 5.
Signups will be handled electronically, as usual. No code freezing is
required. All team members must be present at the demo. During the demo, make
sure you tell us what features you have implemented. Functionality you don't
show us or that doesn't work will not be given credit.
Final writeups and code and content submission is due on Friday, December 7 at
5:00pm. To submit your video game files, simply change the current directory
to your project #3 directory and run the submit script, as you did for
the first two assignments. Only one submission per team is necessary. Your
submission should include your entire game - source, executable, makefiles,
models, textures, etc. It should also include a README file which lists your
team members, describes how to build and run your video game, and explains the
2*N (or more!) advanced computer graphics techniques you implemented.
Also, your README file should include references to any external sources you
referred to for inspiration, and it should indicate how your 3D models and
other game content were obtained. Remember - no late demonstrations or writeup
submissions will be accepted.
Separately from your joint team submission, and privately, each team member
should send an email message to firstname.lastname@example.org by
5:00pm on December 7 specifying who worked on which features of your game, and
what percentage of the total work each team member did.
The video game competition.
After the demos are finished, probably around 4:00pm (on December 5), a jury of
computer graphics experts from industry and academia will join the CS 248
teaching staff to to evaluate your programs as part of a video game
competition. Any team may participate in the competition; however,
participation is not required. There will be one grand prize - an
all-expenses-paid trip to Siggraph 2002
in San Antonio next summer, one second-place prize -
dinner for two at Il Fornaio
in Palo Alto and a choice of any PC video game offered by Electronic Arts, and
some number of runner-up prizes - probably PC video games offered by Electronic
Arts. If the grand prize is won by a team, it must be split among the team
members. All other prizes will be duplicated as necessary to cover the team.
The competition will be accompanied by an amazing party.
As a prerequisite to entering the video game competition, each team must create
a web page for their project. The page should have a title, a paragraph
describing the game, and links to one or more screen-shots. The links to the
full-size screen shots should be by clicking on downsized versions of these
images, each 128 pixels tall. After the competition, entrants will be asked to
provide compressed "tar balls" or zip files for distribution of their game,
along with an indication of the target platform. Any team that does not wish
to enter the video game competition but would like their game distributed is
also encouraged to create such a web page. Teams who do not enter the
competition do not need to create one.
Good luck, and have fun!
Copyright © 2001 Marc Levoy
November 6, 2001 11:30:55 AM