CS 446: Real-Time Rendering
Assignment #3

Synopsis: Build the basic underpinnings of a 3D scene-graph engine.  Your program should be able to import 3D models with hierarchical transformations, place them into a scene graph, and render the scene.  Your scene graph should support multiple traversals (for example, to render the scene from multiple interactively controlled cameras), along with basic view-frustum culling and basic LOD.  Finally, your group should decide on and propose the game you will build.

Due: This assignment has multiple components, each quite challenging in its own right.  To help you organize your effort, we will check your progress midway through:

    Feb 23, 2006   Checkpoint: Load and fly around multiple models (40%)
    Mar 2, 2006   Final assignment: Everything else (60%)

Details: This is where you start: in this assignment your group will build a basic scene-graph renderer that will become the base of your game engine.  Your renderer should support:

• Importing 3D models: your program will support loading multiple 3D models in one or more file formats.  Suggested file formats include .obj (alias/wavefront objects), .md2 (QuakeII), .md3 (QuakeIII), .flt (OpenFlight), .3ds (3D Studio Max), .ma (Maya ascii).  These formats are listed roughly in order of complexity.  The .obj file format is quite simple, but it will be difficult to find or create interesting models.  The .3ds format is fairly complex, but many, many models are publicly available. 
• Hierarchical transformations: your program should support hierarchical transformations in the organization of objects within the scene; for example, if a statue sits on a table and the table is moved, the statue should move with it.  Your program may optionally support hierarchical transforms within a single model, i.e. for articulated characters.  Note that only some of the file formats above (.flt, .3ds, .ma) support hierarchical models.  If you choose not to implement such a file format, you must write your own scene description file that describes the objects in the scene and their organization (I suggest using XML for this, as it is powerful, flexible, extensible, and human-readable, and since tools like libxml can alleviate much of the pain and suffering of parsing).  Note that you don't (yet) need to support loading "levels", in the sense of maps, terrains, or background objects like walls, ceilings, etc.
• Instancing: your program should support instancing, in which a single model can be represented (instantiated) multiple times with different transforms and different graphics state.
• Moving objects: your program should allow the user to pick an object and translate or rotate it within the scene (of course, hierarchical transformations should be respected, so that any children of the selected object are also affected by the user's actions on the parent object).  You should use the mouse to control translation and rotation (e.g., left button translates X/Y; middle button translates Z; right button rotates) and either use the mouse to select objects, or a keystroke to cycle through which object is selected.
• Simple texturing and lighting: You should be able to load and display models with simple texturing and/or lighting.  The user or scene file should be able to specify the rendering state (texture on/off, lighting on/off, wireframe on/off) for each object or instance.  The interface is less important than the functionality here; I suggest "T", "L", and "W" keystrokes to toggle each state for the selected objects. Directional lighting and simple texture modes are fine for now; you should also implement point-light sources associated with nodes in your scene graph.
• Simple distance-switched discrete LOD: Objects may be represented by multiple LODs depending on the distance from the viewpoint to the object. These distances can be set manually or automatically.
• Hierarchical view-frustum culling: Off-screen objects are not drawn.  Calculate and store bounding volumes with subtrees in your scene graph, and avoid rendering off-screen objects by testing those bounding volumes against the planes of the view frustum.  Bounding volumes should be correctly updated with object transformations.  To account for animated objects, you may either pick a bounding volume large enough to contain the object at all steps of the animation, or incrementally update the volume.
• Multiple viewpoints/traversals: The user should be able to switch between multiple cameras, for instance first- and third-person perspectives. One particular traversal you should support is a "top-down" view showing the effects of culling (draw the view-frustum and show objects disappearing when they leave it) and LOD (objects get simpler with increasing distance).  Note that in this kind of view, the camera used for LOD and visibility culling is not the same one used in rendering.  This top-down view is an invaluable debugging tool that you will need throughout the class!
• Interactive camera control: Your program should provide interactive mouse-based camera control (you may implement a keyboard interface in addition if you wish).
• Propose your game concept: You should write a formal proposal describing the game that your group intends to create over the course of the semester: concept, gameplay, visuals, and core real-time rendering techniques.  Your proposal should detail the overall shape of your game, the technical contributions that your engine will incorporate, and (where you know) who will code what.  You should include some hand-made "screenshots" to help explain the intended gameplay and visuals. You should have a game plan for staged development, so that if your full-fledged game proves beyond the scope of the semester, you will still develop something fun and interesting.  In response I will provide feedback on your ideas, whether you're being too ambitious or not ambitious enough, and perhaps some (hopefully) useful advice. 

Resources: There are many places you can go to look for advice, tutorials, details, and source code for games, from loading file formats to AI and physics.  This can be frustrating, however, as many of the resources on the Web are the results of enthusiastic amateurs rather than paid professionals.  Some good places to start are:

• www.gamasutra.com: Lots of useful information on game programming here, along with the usual chaff.
• http://www.gametutorials.com: a soup-to-nuts series of source code "tutorials" on game programming, written for beginning programmers but containing some useful information.  The tutorials are in the form of heavily-commented source code.  In particular there are fairly good tutorials on loading some different 3D file formats. Update: These used to be free; at a glance it looks like now they are charging (the idea is that you buy a whole CD with all zillion tutorials for $50, or one with all the 3D graphics tutorials for $20).
• http://lib3ds.sourceforge.net: a library for reading .3ds files, seems fairly complete.
• www.planetquake.com/polycount: lots of models for various games. 
• http://www.turbosquid.com: Models, textures, and other assorted downloads for 3D graphics & game development. Some stuff for free, lots of stuff for sale (often at extremely low prices).
• 3D Studio Max files: I have purchased a collection of over 5000 models in 3D Studio .max  format (not the same as .3ds), available at \\eirene.cs.virginia.edu\3dEnc2000 in Windows.  You can export these models (for example, to .3ds format...) and create new ones using 3D Studio Max, which is (or will be) available in 002a. You can browse these models more conveniently at http://www.deespona.com/3denciclopedia/menu.html.
• Note that we also have Maya, another modeling package.  If you want to use Maya we should be able to accommodate you. There is a lot of Maya expertise on Grounds, both here in the CS department (including your very own TA) and in the Digital Media Lab in Clemons Library, which has lots of FAST machines with Maya installed and employees (some anyway) who are expert in its use.

Also, don't forget about the optional texts for the course like the GPU Gems series!

Lab: We are sharing Olsson 002a this semester.  Many of you will need to get a key from Ginny Hilton at the CS front desk (if you already have a key, for example, to 001, check first to see if it works).  There are 13 machines and ~25 students in this class, plus occasional students in other classes using the lab...so be courteous and don't assume you will always get a computer exactly when you were planning to work.  The machines in 002 have decent processors and decent (ATI X600) graphics cards; I will be installing a few GeForce 7-class cards (the latest programmable graphics cards from NVIDIA) later. My tentative plan is to have one very high-end card installed for testing purposes, and a bunch of low-end but latest-generation cards for development. If you would rather work on a personal machine, that's fine too -- in fact it will take the pressure off the lab machines.  Let me know any issues you encounter -- this is an unusual use of this lab and there will undoubtedly be software, hardware, and availability issues to work out.

Policy on code reuse: In general you are welcome to use code that you find elsewhere.  For example, you are welcome to use the lib3ds library mentioned above, and you are encouraged to use our in-house software tools (linked to from the main page).  However, you will not get credit for what you didn't write.  Therefore, it is critically important that you describe in detail what code you wrote yourself and what code you imported or adapted from elsewhere.  Furthermore, if you find a particularly helpful library, tutorial, loader, etc., you should post it on the forum.  Obviously if you reuse a significant amount of code, that raises the bar for the assignment: you will be expected to do something beyond the basics mentioned above.  If you have any questions about code reuse or attribution, please ask me.

Platform: I would prefer that your code compile and run under Microsoft Visual Studio .NET 2003, which is what is installed in the lab. Please don't use VS.NET 2005 beta. If your entire group wants to develop under Linux or Macintosh, go ahead.  Any Linux projects should compile and run on the lab machines; this may require intervention by root (to install libraries, etc) so don't put off testing your code down there.  If you go Mac, you will need to work with me to make sure one of our few Macs can run your code. You are welcome to use any GL extensions supported by NVIDIA or ATI cards.  If you want to use a particular input device (joystick or whatever), talk to me first...you may have to lend it to us so we can grade your assignment.

Turning in the assignment: Checkpoint: Demo to the instructor or TA that you can load and fly around multiple models.  Final assignment: Put all your code and models in a folder, along with a detailed README.txt file that describes what your group did, who in the group did what, what code you wrote and what code you used from elsewhere, and how to run your assignment.  Zip up the folder and e-mail the .zip file (or a link) to me and the TA.  Be sure to include workspace and project files, along with any libraries/include files/etc, so that we can compile your code.  We will read (and grade you on) your source code, so follow good programming practices.

Advice: If this sounds like a lot for a two-week assignment, that's because it is a lot.  An awful lot. This will be the hardest assignment in terms of the sheer amount of code you need to write.  It is particularly important to start early because you will be building on this code for the remainder of the course; a careful and thoughtful design now will simplify everything down the road, whereas a rush job will introduce bugs and design flaws that will continue to bite you throughout the semester.  Now is the time to follow good careful software engineering practices: think carefully about your design BEFORE you start, test your classes and functions early and often, and use CVS to back up your work for disaster recovery and revision control.