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Josh Sanders

OpenGL C++/OpenGL Chess Game Project

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So, I'm a student at UHV and I'm taking a class called Computer Graphics Applications, as is required for my degree in Computer Science - Digital Gaming and Simulation. We were assigned a final project, and I want to start working on that project now so that I can refine it until it is perfect by the end of the semester. I chose a chess game, rendered with OpenGL.
This would do three things for me: (1) Help to make me more fluent in C++. (2) Help solidify OOP concepts I've been learning. (3) Give me a head start into Game AI before I take the AI class next semester
So, I'm not sure if i will get much help on here, but any would be much appreciated. I'm not looking for somebody to tell me all of the answers, I would like to figure the code out on my own, but pointing me to the right concepts is what I really need. At this point, I'm not sure where to start.. Here is what I have:
Classes: RED
SubClasses: GREEN
Data Members: BLUE
Functions: PURPLE

enum TurnState
playerOneTurn,playerTwoTurn,Stopped
enum GameState
playerOneCheck
playerTwoCheck
playerOnecCheckMate
PlayerTwoCheckMate
InitializingGame
Tie
NormalPlay

- [color=#ff0000]Player(abstract class)[/color]
- [color=#008000]Computer(inherits from Player)[/color]
- [color=#ff0000]ChessGame[/color]
- [color=#0000ff]Player p1, p2[/color]
-[color=#0000ff]TurnState turnState[/color]
- [color=#0000ff]GameState gamState[/color]
- [color=#ff0000]Move[/color]
- [color=#0000ff]*Piece[/color]
- [color=#0000ff]Location origin[/color]
- [color=#0000ff]Location destination[/color]
- [color=#ff0000]Location[/color]
- r[color=#0000ff]ow[/color]
- [color=#0000ff]col[/color]
- [color=#0000ff]*ChessBoard[/color]
- [color=#ff0000]ChessBoard[/color]
-[color=#800080]isValid(move) //checks if the move is valid[/color]
- [color=#ff0000]ChessPiece[/color](abstract class)
- [color=#800080]GetValue() //returns an int value of the peice(for scoring)[/color]
- [color=#800080]GetPosition() //returns the current position of a piece[/color]
- [color=#800080]getIsSelected() //returns a boolean, true if selected, fale if unselected[/color]
- [color=#800080]move() // moves the piece in a way dependent upon what piece[/color]
- [color=#008000]Pawn[/color]
- [color=#008000]Rook[/color]
- [color=#008000]Queen[/color]
- [color=#008000]King[/color]
- [color=#008000]Knight[/color]

So this is what I have so far. All of the pieces will inherit methods from Piece and be able to override those methods. But I have several questions:
Where and how do I tie OpenGL into this? What classes should have openGL code in them? Should I make seperate classes for openGL??
Do I still make a 2d array in memory to store the position of the pieces? Or is eveyrthing done on screen? For example, would I say, " rook location is [1][3]" or would I tell openGL "When I click on this part of the screen, select the rook", or both?

Are there classes I should add? What other functions will I need? How do i get started?

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The data structures you use to represent current game state should not depend on how it is drawn using OpenGL. That way, you can easily change the appearance if you want to make a more advanced solution without having to change anything in the main game state. You can start with making a chess game that simply prints out the positions on the dos prompt using character representations for pieces. When that works, you can replace the print functions with an interface to OpenGL, or whatever library you find.

This is a basic technique of programming. To keep the model independent on the display, sometimes called [url="http://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller"]Model-View-Controller[/url]. The purpose is to minimize the need for changes propagating too far in the source code. Because changes will never stop.

Learning to use OpenGL can take a couple of months if you are experienced with C. You have to decide if you want to go for a 3D view. That would be looking at the chess board from above, with an angle. It will look the best, but requires more effort. An easier way is to divide the screen into 8x8 areas, and simply draw different bitmaps at each position. This is easier, but still the effort to get OpenGL up and running will take a lot of effort.

There are also 3:rd party game engines that can help you, so that you don't have to worry too much about the low level details. Someone else will have to give recommendations for this.

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opengl is _only_ and i mean _only_ a rasterizer.. all it does is draw stuff
you can use gpu to calculate things and get return data, but that is beyond opengl

as for pawn, i would split pawn into 2 subclasses: PawnWhite and PawnBlack, since they move very differently

for selecting a piece, you would have to use a window-library that gives you mouse events and the like
java already has this [img]http://public.gamedev.net//public/style_emoticons/default/smile.png[/img]

EDIT: i see now that you intend to use c++, then i recommend freeglut or glfw for opengl frontend
this should get you started though (if indeed you have to use c++, since its quite a bit harder learning curve for opengl)

sorry for the short reply, and good luck Edited by Kaptein

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Okay, first of all, thank you very much for the response! So it seems clear to me that I should write the game first, making everything modular, and then worry about openGL. So, if you would, please allow me to document my thought process here, maybe I will make this thread my diary, with you as my guidance .
So, I sat down in Visual Studio 2012, and I made all of my classes. And Then I thought, it would be better if I created the classes as I needed them. So, I started with my ChessGame class. Then my thoughts are, I should create a GameBoard right? So I made a GameBoard class, and tried to develop an algorithm that would create the board:

Problem: I need to create an 8X8 array that will serve as my chessboard. Each spot in the array will be white or black, and empty or containing a piece.

Solution 1:
Make an 8X8 int array. If it was an int array, I could specify if it were white and black by filling the array with 1's and 0's!
However, then I thought, how would I tell the program that there is a piece in that spot? And more importantly, what piece is in that spot?

Solution 2:
Make a class called Spaces and fill the array with Spaces that have a white parameter, a black parameter, and a pointer to the piece that lies on it, if any. But would this make sense? Should i have a Space class with WhiteSpace and BlackSpace subclasses? But I think this could impose another problem. First of all, each space would be a new object which.. sounds a little extreme. And secondly, Each space would have a unique name, although I suppose I could name them as coordinates. Maybe I could use structs instead?

Which brings me to the structure of my pieces. Should I have WhitePiece and BlackPiece classes? Could both of these problems be solved with an enum? Edited by frostbytes89

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[quote name='frostbytes89' timestamp='1347507798' post='4979563']
...
So, I sat down in Visual Studio 2012, and I made all of my classes. And Then I thought, it would be better if I created the classes as I needed them. So, I started with my ChessGame class. Then my thoughts are, I should create a GameBoard right? So I made a GameBoard class, and tried to develop an algorithm that would create the board:
...
[/quote]

You really were on the right path. Make your design up-front to avoid a lot of problems later. Writing the code should be really just that, writing code, not thinking about how/where/what to write. Think of building software as-if you're building a house. Houses need a design up front to prevent making mistakes early in the construction process (eg building walls that dont support a heavy roof), the same holds true for software.
And while you're at the design process you should really have a look at UML, it's pretty standard and alot more clear than fancy text colors. For tool you can have a look at violet uml editor, it's good for very basic designs.

As for your last question, are WhitePiece and BlackPiece really fundamentally different from eachother? Or is it just some of the behaviour that needs to change?
Also, dont worry about object count, as long as you're not making any mistakes resulting in constant copy-ing of objects, you can use many thousands of objects.

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[quote]As for your last question, are WhitePiece and BlackPiece really fundamentally different from eachother? Or is it just some of the behaviour that needs to change?
Also, dont worry about object count, as long as you're not making any mistakes resulting in constant copy-ing of objects, you can use many thousands of objects.[/quote]




Well, I thought about that, and I think the reason I came up with to make them two seperate classes, is that it might make it easier in the long run to program which moves a piece like say, the bishop is allowed to move. So Maybe I could say in psuedocode, if bishop is on black space, he can only move along other black pieces. But it seems like an enum would be better than making an entire class and object based on color. I was just thinking of the "is a" relationship, and a "has a" relationship. So the board HAS spaces, which ARE colors. So Board class is by himself. Space class is by itself with it's color that it IS rather than has. But I may be stretching that too far..

But holy crap rongshuxiacy I actually have that book right here and I've never looked into it!! I bought this book like.. 6 years ago and never thought to open it now because I was sure that all of the info and methods would be outdated and depricated. But I guess the main reason I didn't look is because I wanted to try and solve these issues without actually seeing a coded solution. I mean what use am I as a programmer if I can't even do something like this... I guess I would feel like I was cheating.

And as for the UML, I will have a look at that. I remember doing a UML back in my freshman classes. It certainly might make it easier for me to convey my code logic. And thanks for saying I'm at least on the right path

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they [pawns] are indeed fundamentally different on the movement level, and i personally chose to make Pawn -> PawnWhite, PawnBlack
it's a matter of semantics though
the hardest part is probably keeping up with some the special rules (castling, en-passant), and making sure the players aren't making illegal moves
there are some cheap tricks though =) in my PawnWhite class i simply checked if the pawn was at say y=2, then there were 2 valid moves,
since the first move by a pawn allows 1 or 2 steps forward.
i used a boolean map reference as return value for move tests, and while it certainly isnt very fast, it wasnt slow either when you dont have to write an AI [img]http://public.gamedev.net//public/style_emoticons/default/smile.png[/img]
it wasnt any sort of final assignment though, just a small school project, so i dont know how far you want to go with this
playing chess is an art, but.. coding the best chess program and keeping up with the latest, is probably a more than one persons lifes work
so, my last advice is: first and foremost - make it (just) work!
presentation and visuals counts more than AI to most people, even the old professors [img]http://public.gamedev.net//public/style_emoticons/default/smile.png[/img] it should feel like a chessboard!
just in case though, i would probably ask what is expected... Edited by Kaptein

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