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

llvllatrix

Author

340

January 07, 2005 04:13 PM

Hey guys,

sry for the long wait. I was busy preparing this:

http://www.eng.uwaterloo.ca/~rramraj/Gamedev/chess_tutorial/src_tree/chess_src.zip

It's a fully functional implementation of the subsystems we have discussed so far. You can find our source tree in the console basecode. I also made a few changes to the implementation of the context manager.

You'll notice that some lines are commented out in our main function where the unit tests are. What exactly is a unit test? A unit test is code that "proves" the functionality of a particular subsystem. The test is not responsible for dealing with the errors that pop up per say. It simply puts the subsystem through its paces. If there are any problems, it's the responsibility of the developer watching the test to deal with them accordingly.

You'll also notice that I've included my own gl basecode in with the source. The code is similar to nehe's but I've also included a set of libraries that will let us do modeling, texture loading, and math. For those that want to read ahead its a good place to start. We will be using toned down versions of these libraries in our resource manager.

So, grab a cup of hot chocolate, sit in front of the fire place, and prepare yourself for a trek into the source. Its a story of love, betrayal, and ambition ;) At the moment I have to turn my attention a bit to the winamp gl contest; need to get the demos online. Check 'em out if you have the time :) I'll try to get the sound loader online asap.

Will post later,
- llvllatrix

Keermalec

122

January 08, 2005 05:08 AM

Without meaning to question the excellent work you are doing Ivllatrix, why not just focus on the game by making the windows creation/management code as simple as possible for the time being; for example by using GLUT or SDL? For a simple project like this it seems better to develope the gaming code first and concentrate later on the interface code. It may also be less confusing for a beginner.

For example, here is the chess board in just 80 lines of code using glut:

// Basic 60-line Glut code from http://personal.nbnet.nb.ca/daveg/opengl/misc/#PicoCube#include <GL/glut.h>void reshapeFunc( int w, int h ){   glViewport( 0, 0, w, h );   glMatrixMode( GL_PROJECTION );   glLoadIdentity();   if( h < 1 ) h = 1;   gluPerspective( 30.0, (double)w / (double)h, 1.0, 1000.0 );   glMatrixMode( GL_MODELVIEW );}void draw_board(void){	int x, z;	for (x = 0; x < 8; x++)	{		for (z = 0; z < 8; z++)		{			float col = (float)((x % 2) ^ (z % 2));			glColor3f(col, col, col);			glPushMatrix();			glTranslatef((float)(2*x), 0, (float)(2*z));			glBegin(GL_QUADS);			glVertex3f(-1.0f, 0.0f, 1.0f);			glVertex3f( 1.0f, 0.0f, 1.0f);			glVertex3f( 1.0f, 0.0f,-1.0f);			glVertex3f(-1.0f, 0.0f,-1.0f);			glEnd();			glPopMatrix();		}	}}void displayFunc(void){	static GLfloat angle1 = 0.0f;	angle1 += 1.0f;	glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );	glLoadIdentity();						// Cancels all transformations	gluLookAt(	20.0f, 15.0f, 20.0f,		// Camera position				0.0f, 0.0f, 0.0f,			// Camera direction				0, 1, 0 );					// Camera up vector	glPushMatrix();							// Objects rendered between push and popMatrix will be transformed without affecting camera	glRotatef( angle1, 0.0f, 1.0f, 0.0f );	// Rotates objects which follow	glTranslatef( -7.0, 0.0, -7.0 );		// Centers board on coords 0,0,0	draw_board();	glPopMatrix();							// Objects rendered between push and popMatrix will be transformed without affecting camera	glutSwapBuffers();	glutPostRedisplay();}void keyboardFunc( unsigned char key, int x, int y ){	switch( key )	{		case 27: // ESC key			glutDestroyWindow( glutGetWindow() );			exit( 0 );	}}int main( int argc, char* argv[] ){	glutInit( &argc, argv );	glutInitWindowSize(640, 480);	glutInitDisplayMode( GLUT_DOUBLE | GLUT_DEPTH | GLUT_RGB );	(void)glutCreateWindow("Basic Glut App");	glutReshapeFunc( reshapeFunc );	glutDisplayFunc( displayFunc );	glutKeyboardFunc( keyboardFunc );	glClearColor( 0.0, 0.75, 0.75, 0.0 );	glEnable( GL_DEPTH_TEST );	glutMainLoop();	return 0;  // Never called!  glutMainLoop() never returns....}

da_grat1

122

January 08, 2005 06:34 AM

keermalec...
Yeah that code is simple and easy to understand... It would be nice if we can display a menu screen for the game.... :)

Quote: At the moment I have to turn my attention a bit to the winamp gl contest; need to get the demos online. Check 'em out if you have the time :) I'll try to get the sound loader online asap.

yes I will check the demos... :)

llvllatrix

Author

340

January 08, 2005 01:50 PM

Quote:
Without meaning to question the excellent work you are doing Ivllatrix

lol, no worries :) As I said, questioning my work is very valuable because it lets us further our discussion.

Quote:
why not just focus on the game by making the windows creation/management code as simple as possible for the time being; for example by using GLUT or SDL? For a simple project like this it seems better to develope the gaming code first and concentrate later on the interface code. It may also be less confusing for a beginner.

Actually, that’s a good point. There are several libraries that we can easily use in place of the windows creation subsystem (GLUT and SDL). We could either write our own, use GLUT or use SDL. Keermalec's source uses GLUT and as you can see it is very elegant. Writing our own would essentially consist of a review of nehe's first tutorial. If we wrap our windows creation routines, we can also easily switch between the different options. Are there any preferences?

Thanks Keermalec :),
- llvllatrix

lazork357

148

January 08, 2005 04:34 PM

I think that for such a program, using libraries like GLUT or SDL would be ok.
Generally speaking though, do these libraries limit performances?
I read somewhere that glut, for example, causes a slowdown, compared to something like NeHe's basecode; is this true?

wcm4Him

122

January 08, 2005 10:13 PM

I think GLUT would be a good choice since most of us are probably familiar with it (not to mention this thread is on an OGL website).

[Edited by - wcm4Him on January 10, 2005 1:13:39 PM]

da_grat1

122

January 09, 2005 11:38 AM

llvllatrix, when are u going to continue the chess tutorial.. I think the next tutorial is about the game menu... :)

llvllatrix

Author

340

January 10, 2005 07:21 PM

sry for the long delay...been kinda busy with the winamp contest...

Quote:
llvllatrix, when are u going to continue the chess tutorial.. I think the next tutorial is about the game menu... :)

Unfortunately, we still have a ways to go to get to the game menu, but if its any consolation, once we get there we will be more than half way through our project :D.

My next tutorial will be on sound loading using OpenAL. I expect to be finished the resource manager within this week. When the resource manager and window creation subsystems are done, we can start on the game menu.

Will post later,
- llvllatrix

da_grat1

122

January 11, 2005 09:07 AM

llvllatrix

Do u think this tutorial can be finished within this month...? I think the most difficult part is to implement the artificial intelligent into the game..

lazork357

148

January 11, 2005 11:51 AM

What kind of audio files are you going to use?
Loading WAV files using OpenAL is pretty simple, but loading OGGs can greatly decrease the size of the final application (could be useful since it's going to be downloadable; or isn't it?)

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