How to program a chess: a forum based tutorial

llvllatrix · 2005-04-02T02:01:34

Introductions (ie what the heck is this thread about): This thread was born when da_grat1 asked me about model loading. After a bit of discussion it turned out that he was trying to program a chess game and wondered if I had any advice. The result; a good excuse to talk design. Although this may seem off topic on this forum, I think nehe is best for several reasons. This forum has a wide variety of visitors, both advanced and beginner (you'll see why this is important later...keep reading :) ). I also dont have to go over OGL, which we will be using to do our graphics. Most of you have also already taken a look at some general demo design as well as loading and playing sound, which is a bonus. Also note that da_grat1 will be trying to implement this, so I'm going to try my best to keep us on topic and drive us through the end. k, so its obvious that i cant tell you that if you follow steps 1 - X you'll successfully complete your project, or game ect. (lol, its just not possible) Instead, what I want to do with this thread is to start a discussion about game design from start to where ever we take it. Consider this an online, dynamic tutorial with many authors. You guys should feel free to tell me that I'm wrong (giving a reason for your decisions is very important because we are all of different expertise in different areas). Remember that even if you feel you cannot contribute because you dont have the experience, asking questions is just as valuable (they determine where this discussion will go). Questions you guys ask will determine what issues get addressed and in what order. So sit back and get ready for what will hopefully be a long and productive discussion. I think the best place to start is at the beginning. You'd be surprised how many people dont start there. Imagine how terrible it would be if you hired a company to build you a corporate headquarters for your multi-million dollar game development studio and when you open the door, the thing crashes down on you. Then, when your in your hospital bed you find out that its because the guys who built the place didnt do any planning or draw any blue prints and just started building the place without thinking twice. The reason this kind of thing doesn't happen with building companies is because architects and engineers design and test the building long before anyone uses a hammer or saw. However, this happens all to often in software engineering; people just dont start at the beginning. They jump into projects and start coding without design documents. Remember your friend who said he would make an amazing game and ended up not finishing it? Its because when he was nailing some code together, the structure fell straight down on top of his head and he couldnt continue...anyway I tink I made my point...design twice, build once...so lets get to some code design...that and I ran out of building analogies ;) ... Programming is like chewing a pack of bubble gum. If you chew it all at once you're going to die. Its best if you divide the pack into pieces and chew each separately. There’s no guarantee you're not going to choke on a small piece but at least if you do you can probably spit it back up. So the first thing to do is establish exactly what we hope to accomplish and then keep breaking it down till we can implement it. To break it down on a business level, the "what are we going to do" is the project proposal. The "break down" is the design document/feasibility study and the implement it is "code till it works". Side trackin': In this quick paragraph I'm going to describe my tendencies when it comes to game programming. Most of the reasons for this stuff comes from code on the cob (http://www.gamedev.net/reference/list.asp?categoryid=45#115) and we'll hopefully see it used and justified further on in the discussion. Game programming (unlike word processors) are made using synthesis. We are going to take elements like graphics, audio ect and put them together to make a product. To do the synthesis I typically use function libraries as the glue that holds my program together (think OpenGL's interface). Classes and inheritance usually dont work for this kind of thing (think MFC). I'm not saying to totally abandon classes, I'm saying "use them to do a job behind a function library so that whatever uses the library doesn’t have to know about them". Keep your interfaces clean and whatever you build with them will look ok...irregardless of what is behind the interface. What are we going to do? So we're making a chess game. It will have 3d pieces that move accross the board (as apposed to appearing where ever you clicked), an animated camera, ai which you can play against (not good ai, but ai none the less), a console for testing (not as complex as you think, but it will just take a long time to implement), sound for coolness, and the ability to save your game. That sound good to everyone? How are we going to do this? Well, first step is decomposition, but what exactly does that mean? If you refer to my side track up there, why are we decomposing, shouldn’t we be synthesizing? In truth, there are actually two different phases here that use different techniques to get their jobs done. The first phase is the design phase where we decompose our problem into sub problems till we are satisfied we can tackle them. Then we go to the implementation phase where we take the easiest sub problems, solve them, and their solutions to solve larger problems till we have a final solution; our game (this is what i mean by synthesis). So what is this design thingy all about? Decomposition is the answer to the question, "how the hell am i supposed to do that?" Design is about making a decomposition that works both now and in the future (you'll see what i mean). Pop quiz: what did a software blue print look like back when king tut was writing security software for his sarcophagus (namely the 7 Egyptian curses of death)? Ans: Same as they look today ; a pyramid. On the top of the pyramid is our goal (namely, a game) and on the very bottom is stuff we know we have to use to achieve our goal (our requirements). I our case, we have stuff like OpenGL, Windows, and fmod on the bottom. At the top of our pyramid is our chess game. Let the designing begin: A quick way to start is by listing a bunch of stuff you're probably going to need. In any game, we're going to need a main screen (the thing people see when they start the game), a game screen(the game itself), a menu (drawn over the screen), a way to tell if the game is over, a way to tell what screen gets input, a way to get the input, a way to keep track of time, a way to draw objects as apposed to triangles, a way to easily play a sound, a way to load files, a way for the ai to think, a way to control the camera, and a whole bunch of other stuff. The next thing to tackle is to organize this stuff in a pyramid and then fill in the gaps where we need to. We then keep doing this (decomposing these subsystems) till we can implement each subsystem without having to decompose it. So the next thing to tackle is to rearrange the subsystems i've listed (as well as others you guys come up with) into the pyramid and this i'm going to leave to anyone with time on their hands (this is a good exercise to do) or to my next post (which ever comes first). will post later, - llvllatrix

da_grat1

122

January 20, 2005 09:08 PM

How many subsystems all together?

llvllatrix

Author

340

January 20, 2005 09:37 PM

Just 1 :) This is the power of abstraction. DevIL will load all of these file types and all you have to do is pass it the path to the image file. I've got the code done and I'm reviewing it right now...

After that its on to the subsystem you've all been waiting for; model loading :D

Pop quiz:
Why should you always make accessors and modifiers for your class's data members (even if its a straight pass)?
Answer:
So you can add one later if you want to :)

Will post later,
- llvllatrix

llvllatrix

Author

340

January 20, 2005 10:59 PM

Hey guys,

You can download the new source from:

You can download a the new source code at:
http://www.eng.uwaterloo.ca/~rramraj/Gamedev/chess_tutorial/src_tree/chess_src.zip

It should be straight forward; You can find info on the DevIL (OpenIL) SDK in inc_os_dev_il.h.

Cheers,
- llvllatrix

da_grat1

122

January 21, 2005 05:34 AM

Wow..great... I tested it.. but when i try to open image with 1024 * 640 dimension...it says "image dimension incorrect".. I can only open an image with 1280 * 1024 dimension.. :) why is it like that?..

llvllatrix

Author

340

January 21, 2005 10:36 AM

OpenGL can only create textures that have dimentions which are of power 2. When I wrote the code, I thought that people would prefer to resize the texture themselves (so that they can approve of the result) rather than have an algorithm do it when the texture loads (which can potentially cause artifacts in the texture).

Will post later,
- llvllatrix

wcm4Him

122

January 21, 2005 12:50 PM

So are we finshed with the sound resource than and we're moving onto the graphics now??

llvllatrix

Author

340

January 21, 2005 01:30 PM

Quote:
So are we finshed with the sound resource than and we're moving onto the graphics now??

Yup :) We really dont need anything too complicated for sound.

We've roughly divided the bottom layer of our pyramid into two parts; the resource library and the utility library. Components of the resource library either currently use the disk or could potentially use the disk in the future. Components of the utility library will never use the disk (timers ect).

The reason for the division is for a feature we may want to consider adding later on (as our games get more complicated). Professional resource managers are fairly large and complicated because large games have lots of assets to load. Usually the assets are packed into one file. Resources are loaded from disk as they are needed, instead of loading everything into memory at once. Music is also streamed from disk (not as hard as you think; we can actually modify our sound code to do it...managing that code would be the hard part).

Why dont we need to write a resource manager like this? The answer is simple: we can easily load all of our assets into memory. If we were to start another project after this one, upgrading the resource manager would probably be the place to start.

Will post later,
- llvllatrix

da_grat1

122

January 21, 2005 02:54 PM

What types of sound are we using... will we be able to hear a sound when we move the chess piece..

Now we are doing the modal loading part right? is that how we place the chess pieces on the board?

llvllatrix

Author

340

January 21, 2005 03:00 PM

This is how we load and draw the chess pieces in OpenGL. We will technically be able to place the pieces on the board but it will merely be asthetic. We wont be able to play the game yet until we define the game's logic.

Will post later,
- llvllatrix