OpenGL Slow sprites?

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Hi, i have been working on a graphics engine in OpenGL. I load images into SDL surfaces and translates it into a matrix of 256*256 OpenGL textures. But when i drew the image (looping the matrix and draw the textures) it was very slow. On my computer, i had about 60 fps. Im sure its not the vsync. My screen is set to 75 hz and when i make the picture smaller i get 75 hz as expected. Should it be that slow or is it just something wrong with my program? However, here is the code:
//fhTexture.cpp

#include "fhInclude.h"

...

bool fhTexture::Draw( int x, int y, int tx, int ty, int tw, int th )
{
int xofs, yofs;

int cutx = 0, cuty = 0, cutw = FH_SEGMENT_WIDTH, cuth = FH_SEGMENT_HEIGHT;

int xstart = tx / FH_SEGMENT_WIDTH;
int xend = tw / FH_SEGMENT_WIDTH;
int ystart = ty / FH_SEGMENT_HEIGHT;
int yend = th / FH_SEGMENT_HEIGHT;

//Enable GL textures
glEnable(GL_TEXTURE_2D);

for ( int row = ystart; row <= yend; row++ )
{
yofs = y + (row * FH_SEGMENT_HEIGHT) - ty;
for ( int col = xstart; col <= xend; col++ )
{
if ( col == xend )
cutw = tw - (col * FH_SEGMENT_WIDTH);
else
cutw = FH_SEGMENT_WIDTH;

if ( col == xstart )
cutx = tx - (col * FH_SEGMENT_WIDTH);
else
cutx = 0;

if ( row == yend )
cuth = th - (row * FH_SEGMENT_HEIGHT);
else
cuth = FH_SEGMENT_HEIGHT;

if ( row == ystart )
cuty = ty - (row * FH_SEGMENT_HEIGHT);
else
cuty = 0;

xofs = x + (col * FH_SEGMENT_WIDTH) - tx;

glBindTexture(GL_TEXTURE_2D, data[row*cols + col]);

glTexCoord2f( float( cutx ) / FH_SEGMENT_WIDTH, float( cuty ) / FH_SEGMENT_HEIGHT );
glVertex3f( xofs + cutx, yofs + cuty, 0.0f);

glTexCoord2f( float( cutw ) / FH_SEGMENT_WIDTH, float( cuty ) / FH_SEGMENT_HEIGHT );
glVertex3f( xofs + cutw, yofs + cuty, 0.0f);

glTexCoord2f( float( cutw ) / FH_SEGMENT_WIDTH, float( cuth ) / FH_SEGMENT_HEIGHT );
glVertex3f( xofs + cutw, yofs + cuth, 0.0f);

glTexCoord2f( float( cutx ) / FH_SEGMENT_WIDTH, float( cuth ) / FH_SEGMENT_HEIGHT );
glVertex3f( xofs + cutx, yofs + cuth, 0.0f);
glEnd();
}
}

glDisable(GL_TEXTURE_2D);
}

...


//main.cpp

#include "fhInclude.h"

int main(int argc, char *argv[])
{
SDL_Init( SDL_INIT_VIDEO );

SDL_GL_SetAttribute( SDL_GL_RED_SIZE, 8 );
SDL_GL_SetAttribute( SDL_GL_GREEN_SIZE, 8 );
SDL_GL_SetAttribute( SDL_GL_BLUE_SIZE, 8 );

SDL_GL_SetAttribute( SDL_GL_DEPTH_SIZE, 8 );
SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );

SDL_Surface *screen;
screen = SDL_SetVideoMode( 1024, 768, 24, SDL_OPENGL | SDL_SWSURFACE );

glViewport( 0, 0, 1024, 768 );

glMatrixMode( GL_PROJECTION );
glOrtho( 0.0f, 1024.0f, 768.0f, 0.0f, 0.0f, -2.0f );

glClearColor( 0.0f, 0.0f, 0.0f, 0.0f );
glClearDepth( 2.0f );
//glEnable( GL_DEPTH_TEST );
//glDepthFunc( GL_LEQUAL );

glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

glMatrixMode( GL_MODELVIEW );
glTranslatef( 200.0f, 300.0f, 1.0f );

//variables for handling FPS (frames per second)
bool done = false;
SDL_Event evt;
int FPS     = 0;
int pastFPS = 0;
int past    = 0;
int currentTime = 0;

//variabels for key-states
int KeyLeft = 0; //0 means key is up, 1 means its down
int KeyRight = 0;
int KeyUp = 0;
int KeyDown = 0;

int SecKeyLeft = 0; //0 means key is up, 1 means its down
int SecKeyRight = 0;
int SecKeyUp = 0;
int SecKeyDown = 0;

int mode = 0;

fhTexture test;

int x = 0;
int y = 0;

int w = 1024;
int h = 768;

int tx = 0;
int ty = 0;

while( 1 )
{
//Handling FPS counter
if( SDL_PollEvent(&evt) )
{
if (evt.type == SDL_QUIT)
done = true;
}

currentTime = SDL_GetTicks();
past = SDL_GetTicks();
FPS++;

//Checking if one second has passed and printing FPS to top of window
if ( currentTime - pastFPS >= 2000 )
{
static char buffer[20] = {0};
sprintf( buffer, "%d FPS", FPS/2 );
SDL_WM_SetCaption( buffer,0 );
FPS = 0;
pastFPS = currentTime;
}

glClear(GL_COLOR_BUFFER_BIT);
glLoadIdentity(); // Reset the view

test.Draw( x, y, tx, ty, w, h );

SDL_GL_SwapBuffers();

if (mode == 0)
{
//Checking key-states and changing the projection position
if (KeyLeft) x--;
if (KeyRight) x++;
if (KeyUp) y--;
if (KeyDown) y++;
}
else if (mode == 1)
{
if (KeyLeft) w--;
if (KeyRight) w++;
if (KeyUp) h--;
if (KeyDown) h++;
}
else if (mode == 2)
{
if (KeyLeft) tx--;
if (KeyRight) tx++;
if (KeyUp) ty--;
if (KeyDown) ty++;
}
else if (mode == 3)
{
if (KeyLeft) tx--, w--;
if (KeyRight) tx++, w++;
if (KeyUp) ty--, h--;
if (KeyDown) ty++, h++;
}

// Poll for events, and handle the ones we care about.
SDL_Event event;
while (SDL_PollEvent(&event))
{
switch (event.type)
{
case SDL_KEYDOWN:
switch (event.key.keysym.sym)
{
case SDLK_LEFT:
KeyLeft = 1;
break;
case SDLK_RIGHT:
KeyRight = 1;
break;
case SDLK_UP:
KeyUp = 1;
break;
case SDLK_DOWN:
KeyDown = 1;
break;
}
break;

case SDL_KEYUP:
switch (event.key.keysym.sym)
{
case SDLK_ESCAPE:
// If escape is pressed, return (and thus, quit)
test.Free();
return 0;
case SDLK_LEFT:
KeyLeft = 0;
break;
case SDLK_RIGHT:
KeyRight = 0;
break;
case SDLK_UP:
KeyUp = 0;
break;
case SDLK_DOWN:
KeyDown = 0;
break;
case SDLK_SPACE:
mode++;
if (mode == 4) mode = 0;
break;
}
break;

case SDL_QUIT:
return(0);
}
}
}

SDL_Quit();
return 0;
}


The code may not be in its best shape right now. I have tried to fix this thing but only made the code worse [sad] Thanks in advance /Mullvalen

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You are rendering quads individually in immediate mode. Immediate mode is slow, and if you are rendering tons of sprites, it can be very noticeable.

How many sprites are you currently drawing? Is it possible to group the quads by texture in order to avoid changing the texture as much?

If the geometry is static, You will want to look into Display lists. These are much faster than immediate mode, but are extremly slow if you need to change geometry.

If the geometry will need to be modified, you can look into Vertex arrays/VBOs. Vertex Arrays are fairly simple to set up, and VBOs are just an extension of Vertes Arrays.

Edit: Wait, do you mean you have 256*256 ( = 65536) textures? Or do you mean that you have a few textures that are 256 pixels on a side? If its the former, that's your problem right there.

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Hehehe...no, by 256*256 i meant the size of the textures as well.

Btw thanks for helping out :)

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