# OpenGL OpenGL newbie needs help with 2D

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Anyways, before I post my code, let me explain my problem. I am making a 2D OpenGL game.Anyways, I am drawing 16x16 textures to the screen(I know, that's smaller than usual), and I only get 1/4 of my 640x480 window (about 300 tiles total). Any more and the program send me immediately to my "shutdown error" message boxes, and it displays them all. This is odd to me becuase they don't show up if I stay at or under 300 16x16 tiles. Anyways, I must be doing something wrong, since i've heard of opengl 2d games that can easily run 1500 32x32 tiles. Now, onto the code: incs.h
#include <windows.h>
#include <stdio.h>
#include <gl\gl.h>
#include <gl\glu.h>
#include <gl\glaux.h>

#pragma comment(lib,"glu32.lib")
#pragma comment(lib,"opengl32.lib")
#pragma comment(lib,"glaux.lib")

#include "topglobals.h"
#include "topglfunc.h"
#include "classes.h"
#include "globals.h"
#include "glfunc.h"


topglobals.h
#define SMALL_TILE_WIDTH 16
#define SMALL_TILE_HEIGHT 16
#define TILE_WIDTH 32
#define TILE_HEIGHT 32

GLuint bgtex[1];


topglfunc.h
void glEnable2D()
{
int vPort[4];
glGetIntegerv(GL_VIEWPORT,vPort);
glMatrixMode(GL_PROJECTION);
glPushMatrix();
glOrtho(0,vPort[2],0,vPort[3],-1,1);
glMatrixMode(GL_MODELVIEW);
glPushMatrix();
}

void glDisable2D()
{
glMatrixMode(GL_PROJECTION);
glPopMatrix();
glMatrixMode(GL_MODELVIEW);
glPopMatrix();
}


classes.h
struct Tile
{
int x;
int y;
int width;
int height;
GLuint texture[1];
Tile(int startx,int starty,int startwidth,int startheight)
{
x = startx;
y = starty;
width = startwidth;
height = startheight;
}
void draw()
{
glBindTexture(GL_TEXTURE_2D,bgtex[0]);
glEnable2D();
glTexCoord2i(0,0);
glVertex2i((x * width),(y * height));
glTexCoord2i(1,0);
glVertex2i((x * width) + width,(y * height));
glTexCoord2i(1,1);
glVertex2i((x * width) + width,(y * height) + height);
glTexCoord2i(0,1);
glVertex2i((x * width),(y * height) + height);
glEnd();
glDisable2D();
}
};


globals.h
//system variables
HGLRC hRC = NULL;
HDC hDC = NULL;
HWND hWnd = NULL;
HINSTANCE hInstance;

//other variables
bool keys[256];
bool active = true;

//tile varaibles
#define SCREEN_WIDTH 640
#define SCREEN_HEIGHT 480
#define MAP_WIDTH 20
#define MAP_HEIGHT 15
Tile *map[MAP_WIDTH][MAP_HEIGHT];
//Tile *character;

//prototypes
LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);

glfunc.h
AUX_RGBImageRec *LoadBMP(char *Filename)
{
FILE *File = NULL;
if(!Filename)
{
return NULL;
}
File = fopen(Filename,"r");
if(File)
{
fclose(File);
}
return NULL;
}

{
int Status = false;
AUX_RGBImageRec *TextureImage[1];
memset(TextureImage,0,sizeof(void *)*1);
{
Status = true;
glGenTextures(1,&bgtex[0]);
glBindTexture(GL_TEXTURE_2D,bgtex[0]);
glTexImage2D(GL_TEXTURE_2D,0,3,TextureImage[0]->sizeX,TextureImage[0]->sizeY,0,GL_RGB,GL_UNSIGNED_BYTE,TextureImage[0]->data);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
}
if(TextureImage[0])
{
if(TextureImage[0]->data)
{
free(TextureImage[0]->data);
}
free(TextureImage[0]);
}
return Status;
}

int InitGL()
{
{
return false;
}
glEnable(GL_TEXTURE_2D);
glClearColor(0.0f,0.0f,0.0f,0.0f);
glDisable(GL_DEPTH_TEST);
return true;
}

void draw_background()
{
for(int x = 0;x < MAP_WIDTH;x++)
{
for(int y = 0;y < MAP_HEIGHT;y++)
{
map[x][y] = new Tile(x,y,SMALL_TILE_WIDTH,SMALL_TILE_HEIGHT);
map[x][y]->draw();
}
}
}

int DrawGLScene()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
draw_background();
return true;
}

void KillGLWindow()
{
if(hRC)
{
if(!wglMakeCurrent(NULL,NULL))
{
MessageBox(NULL,"Release of DC and RC failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
}
if(!wglDeleteContext(hRC))
{
MessageBox(NULL,"Release rendering context failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
}
hRC = NULL;
}
if(hDC && !ReleaseDC(hWnd,hDC))
{
MessageBox(NULL,"Release device context failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
hDC = NULL;
}
if(hWnd && !DestroyWindow(hWnd))
{
MessageBox(NULL,"Could not release window.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
hWnd = NULL;
}
if(!UnregisterClass("OpenGL",hInstance))
{
MessageBox(NULL,"Could not unregister class.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
hInstance = NULL;
}
}

bool CreateGLWindow(char* title,int width,int height,int bits)
{
GLuint PixelFormat;
WNDCLASS wc;
DWORD dwExstyle;
DWORD dwstyle;
RECT WindowRect;
WindowRect.left = (long)0;
WindowRect.right = (long)width;
WindowRect.top = (long)0;
WindowRect.bottom = (long)height;
hInstance = GetModuleHandle(NULL);
wc.style = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;
wc.lpfnWndProc = (WNDPROC) WndProc;
wc.cbClsExtra = 0;
wc.cbWndExtra = 0;
wc.hInstance = hInstance;
wc.hbrBackground = NULL;
wc.lpszClassName = "OpenGL";
if(!RegisterClass(&wc))
{
MessageBox(NULL,"Failed to register the window class.","ERROR",MB_OK | MB_ICONEXCLAMATION);
return false;
}
dwExstyle = WS_EX_APPWINDOW | WS_EX_WINDOWEDGE;
dwstyle = WS_OVERLAPPEDWINDOW;
if(!(hWnd = CreateWindowEx(dwExstyle,"OpenGL",title,WS_CLIPSIBLINGS | WS_CLIPCHILDREN | dwstyle,0,0,WindowRect.right - WindowRect.left,WindowRect.bottom - WindowRect.top,NULL,NULL,hInstance,NULL)))
{
KillGLWindow();
MessageBox(NULL,"Window creation error.","ERROR",MB_OK | MB_ICONEXCLAMATION);
return false;
}
static PIXELFORMATDESCRIPTOR pfd =
{
sizeof(PIXELFORMATDESCRIPTOR),
1,
PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER,
PFD_TYPE_RGBA,
bits,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
0,
16,
0,
0,
PFD_MAIN_PLANE,
0,
0,
0,
0,
};
if(!(hDC = GetDC(hWnd)))
{
KillGLWindow();
MessageBox(NULL,"Can't create a GL device context.","ERROR",MB_OK | MB_ICONEXCLAMATION);
return false;
}
if(!(PixelFormat = ChoosePixelFormat(hDC,&pfd)))
{
KillGLWindow();
MessageBox(NULL,"Can't find a suitable pixel format.","ERROR",MB_OK + MB_ICONEXCLAMATION);
return false;
}
if(!SetPixelFormat(hDC,PixelFormat,&pfd))
{
KillGLWindow();
MessageBox(NULL,"Can't set the pixel format.","ERROR",MB_OK | MB_ICONEXCLAMATION);
return false;
}
if(!(hRC = wglCreateContext(hDC)))
{
KillGLWindow();
MessageBox(NULL,"Can't create a GL rendering context.","ERROR",MB_OK | MB_ICONEXCLAMATION);
return false;
}
if(!wglMakeCurrent(hDC,hRC))
{
KillGLWindow();
MessageBox(NULL,"Can't activate the GL rendering context.","ERROR",MB_OK | MB_ICONEXCLAMATION);
return false;
}
ShowWindow(hWnd,SW_SHOW);
SetForegroundWindow(hWnd);
SetFocus(hWnd);
if(!InitGL())
{
KillGLWindow();
MessageBox(NULL,"Initialization failed.","ERROR",MB_OK | MB_ICONEXCLAMATION);
return false;
}
return true;
}


and finally, main.cpp
#include "incs.h"

LRESULT CALLBACK WndProc(HWND hWnd,UINT uMsg,WPARAM wParam,LPARAM lParam)
{
switch(uMsg)
{
case WM_ACTIVATE:
if(!HIWORD(wParam))
{
active = true;
}
else
{
active = false;
}
return 0;
case WM_SYSCOMMAND:
switch(wParam)
{
case SC_SCREENSAVE:
case SC_MONITORPOWER:
return 0;
}
break;
case WM_CLOSE:
PostQuitMessage(0);
return 0;
case WM_KEYDOWN:
keys[wParam] = true;
return 0;
case WM_KEYUP:
keys[wParam] = false;
return 0;
}
return DefWindowProc(hWnd,uMsg,wParam,lParam);
}

int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int nCmdShow)
{
MSG msg;
bool done = false;
if(!CreateGLWindow("OpenGL Tiling Test",SCREEN_WIDTH,SCREEN_HEIGHT,16))
{
return 0;
}
while(!done)
{
if(PeekMessage(&msg,NULL,0,0,PM_REMOVE))
{
if(msg.message == WM_QUIT)
{
done = true;
}
else
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
}
else
{
if(active)
{
if(keys[VK_ESCAPE])
{
done = true;
}
else
{
DrawGLScene();
SwapBuffers(hDC);
}
}
}
}
KillGLWindow();
return msg.wParam;
}


Anyways, if someone could please point out my mistake, and maybe show me how to correct it, I would greatly appreciate it. P.S. I have so many files because i'm a bit of an organization freak. Thanks, Lycio [Edited by - lycio on May 12, 2008 8:15:06 PM]

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Do you really need so many tiles?
I mean I don't know if you need them for some purpose, but you could make one big polygon and just tile the texture on it, instead of drawing numerous textured polygons, as this is what I think you do.

You could draw one big polygon and set up a logical grid for movement/position that would not be displayed and which would resemble the tiles structre. I think that would be much more simple and far more efficient.

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Without looking at the code, I"m don't think it's something wrong with your code. So if you can answer these questions it can narrow down the problem.

First, what error are you getting? How many unique 16x16 textures are you using for those 300 tiles? How big is 1 16x16 texture. What graphic card do you have?

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under your globals.h you have this defined:

#define MAP_WIDTH 20
#define MAP_HEIGHT 15
Tile *map[MAP_WIDTH][MAP_HEIGHT];

are you adjusting the MAP_WIDTH and MAP_HEIGHT? 20*15=300 which is why its leading me to believe its those lines of code.

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Alright, I have the background as many tiles since I am eventually going to have some of them be different than the default texture(road, gravel, etc.). Now if there's some way to still do that and lower the tile count, that's great! Also, to answer some other questions i'm using 1 image which I load onto bgtex[0]. Also, I don't understand if you meant quad size per tile, or the size of the image file itself, so i'll answer both. The quad size is 16x16 and the image itself is 824 bytes. Also my Graphics card is an Nvidia GeForce 7600 GS running the latest drivers. Also, I am using 1 unique texture for the background for the moment, but will be adding more after I get this to work.

P.S. wlw_wl how could I tile the 16x16 texture onto a 640x480 surface?

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from the look of your code it looks like this might cause the problem

void draw_background(){	for(int x = 0;x < MAP_WIDTH;x++)	{		for(int y = 0;y < MAP_HEIGHT;y++)		{			map[x][y] = new Tile(x,y,SMALL_TILE_WIDTH,SMALL_TILE_HEIGHT);			map[x][y]->draw();		}	}}

which mean each time you draw a background, you created (MAP_WIDTH*MAP_HEIGHT) number of tiles. What you should do is create the map once and draw it.

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Well, if I were to guess, I would say load the textures in advance, and rather than making a load of new Tile classes every frame, just adjust what textures get rendered to which area of the screen and 2D frustum cull the tiles your not rendering or something. I've never gone into 2D tile games, but that's my guess.

[Edited by - Tenac on May 14, 2008 8:26:53 PM]

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Eep - I think that nhatkthanh is very possibly right. If that's not your problem, then it very probably is a problem.

I haven't read all of your code, but I did look for the usage of that draw_background() method. It would appear that it is being called as part of the rendering of a frame, and is thus called repeatedly. This means that you are allocating new storage space on the heap each frame, without releasing the previously-allocated memory, and are thus doubtless leaking memory, possibly rather quickly.

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Alrighty, thanks a lot guys. I've got it working much better now, and am going to work on using culling to display(well, technically hide the not wanted)other "environment" tiles. So, I have one last question, and then I should be all set. I just can't seem to get blending to work, as I have tried a multitude of code snippets. Anyways, here's the one i'm using now:

rendering code
		glEnable(GL_BLEND);		glBlendFunc(GL_DST_COLOR,GL_ZERO);		glBindTexture(GL_TEXTURE_2D,texture[1]);		glEnable2D();		glBegin(GL_QUADS);		glTexCoord2i(0,0);		glVertex2i((x * width),(y * height));		glTexCoord2i(u,0);		glVertex2i((x * width) + width,(y * height));		glTexCoord2i(u,v);		glVertex2i((x * width) + width,(y * height) + height);		glTexCoord2i(0,v);		glVertex2i((x * width),(y * height) + height);		glEnd();		glDisable2D();		glBlendFunc(GL_ONE,GL_ONE);		glBindTexture(GL_TEXTURE_2D,texture[0]);		glEnable2D();		glBegin(GL_QUADS);		glTexCoord2i(0,0);		glVertex2i((x * width),(y * height));		glTexCoord2i(u,0);		glVertex2i((x * width) + width,(y * height));		glTexCoord2i(u,v);		glVertex2i((x * width) + width,(y * height) + height);		glTexCoord2i(0,v);		glVertex2i((x * width),(y * height) + height);		glEnd();		glDisable2D();		glDisable(GL_BLEND);

NOTE: texture[1] is the mask, texture[0] is the actual image, and this only gets called if texture[1] doesn't equal null. If it does equal null it only draws texture[0] without blending.

I know it's doing something, but i'm not sure what. Anyways, i'll explain the code a bit. This is the draw function I have for my alphatile structure. Now, when I call this code it fills the quad the color i'm trying to get rid of. If someone could tell me what i'm doing wrong, i'd greatly appreciate it.

Also, it wasn't the calling the tile constructor each time, as I called it for all the tiles just once, and it still crashed. I think it was just too much memory used up, as I did something similar when I was using directx and got an error that my variable was going over 2GB.

Thanks to you all,
Lycio

[Edited by - lycio on May 15, 2008 8:15:07 PM]

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I was just wondering if anyone could help me with my image masking code (see above post). If somone could help me with that, i'd greatly appreciate it.

Lycio

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