Sign in to follow this  
Mullvalen

OpenGL Slow sprites?

Recommended Posts

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]);
             
             glBegin(GL_QUADS);
                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 );
glLoadIdentity();
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 );
glLoadIdentity();
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;
test.Load( "image.jpg" );

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

Share this post


Link to post
Share on other sites
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.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this