slow texture render first time

juakob · **Joined:** Sat Jul 31, 2010 12:56 am **Posts:** 6

hi! whenever i try to draw a texture that hadn't been drawn before the method SDL_GL_SwapBuffers() freeze for about 1 or 2 seconds, but once its draw once the method works fast.

somebody knows why this happen?

thanks

NordCoder · **Joined:** Tue Apr 06, 2010 4:54 pm **Posts:** 25

Hi juakob,

Do you mind posting your code that is responsible for rendering your texture(s)?

Also, are you saying this happens with textures drawn after SDL_GL_SwapBuffers()? And how do you know this call is responsible for the freeze?

juakob · **Joined:** Sat Jul 31, 2010 12:56 am **Posts:** 6

here its how i create the texture, sTexture its just a struct that contains info about the texture

Code:

uint cTextureManager::LoadTextureFromMemory(SDL_Surface *surface, std::string file){
   GLuint texture;

   glPixelStorei(GL_UNPACK_ALIGNMENT,4);
   glGenTextures(1,&texture);
   glBindTexture(GL_TEXTURE_2D,texture);

   glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER, GL_NEAREST);
   glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER, GL_NEAREST);

   SDL_PixelFormat *fmt = surface->format;
   //if there is alpha
   if (fmt->Amask)
   {
      gluBuild2DMipmaps(GL_TEXTURE_2D,4,surface->w,surface->h,GL_RGBA,GL_UNSIGNED_BYTE,surface->pixels);
   }
   else // no alpha
   {
      gluBuild2DMipmaps(GL_TEXTURE_2D,3,surface->w,surface->h,GL_RGB,GL_UNSIGNED_BYTE,surface->pixels);
   }
   sTexture Tex;
   Tex.nombreArchivo=file;
   Tex.texture=texture;

   Tex.height=surface->h;
   Tex.width=surface->w;
   SDL_FreeSurface(surface);

   uint place;

    if( m_texture.empty() )
    {
        place = 1;
    }
    else
    {
        place = m_texture.size() + 1;
    }
   //set the map accordingly and return its id/place
   m_texture[ place ] = Tex;

    return place;
}

Here its how i create the plane with the texture

Code:

void cTextureManager::DrawTexture(uint TextureId, GLfloat x, GLfloat y, GLfloat scale, GLfloat rotation , GLfloat red, GLfloat green , GLfloat blue,GLfloat alpha ){
   if(CurrentTexture!=TextureId){
      glBindTexture(GL_TEXTURE_2D,m_texture[TextureId].texture);
      CurrentTexture=TextureId;
   }
   GLfloat width = m_texture[TextureId].width*scale;
   GLfloat height =m_texture[TextureId].height*scale;
   
   glLoadIdentity();
   glTranslatef(x,y,0.0f);
   glScalef(scale,scale,0.0f);
   glRotatef(rotation,0.0f,0.0f,1.0f);
   glBegin(GL_QUADS);

      glColor4f(red,green,blue,alpha);
      //Top-left vertex (corner)
      glTexCoord2f(0, 0);
      glVertex2f(0, 0);

      //Bottom-left vertex (corner)
      glTexCoord2f(0, 1);
      glVertex2f(0, height);

      //Bottom-right vertex (corner)
      glTexCoord2f(1, 1);
      glVertex2f(width, height);

      //Top-right vertex (corner)
      glTexCoord2f(1, 0);
      glVertex2f(width, 0);
   glEnd();


}

and then i just call
SDL_GL_SwapBuffers()

I know it freeze because i use breakpoints and when i run that line its freeze for a second or 2

Tim · **Posted:** Mon Aug 02, 2010 9:19 am

Just to confirm - is your texture a power of 2 texture?

juakob · **Joined:** Sat Jul 31, 2010 12:56 am **Posts:** 6

i load 3 textures one of 128x128 and two of 512x512.
The strange thing its why only the first time it render it cause that anomaly.
Im really new to opengl so i dont really know when the texture is copied to video card memory, it the only thing i can think about opengl that can be so expensive to do.

juakob · **Joined:** Sat Jul 31, 2010 12:56 am **Posts:** 6

I found this only happen with images that have alpha channel.
maybe i made a mistake in this line

Code:

gluBuild2DMipmaps(GL_TEXTURE_2D,4,surface->w,surface->h,GL_RGBA,GL_UNSIGNED_BYTE,surface->pixels);

or something else...

juakob · **Joined:** Sat Jul 31, 2010 12:56 am **Posts:** 6

i found that if you compile a release and run the exe this problem dosent happen, but if you run inside visual studio you the freez.

the solution i made was to add this line when you create a texture

Code:

#ifdef _DEBUG
   DrawTexture(texture,0,0,0,0,1,1,1,0);
#endif

that way you render when you load and you dont have to worry about a future freez

Tim · **Posted:** Sun Aug 08, 2010 8:44 pm

Perhaps it has to do something with the debugger. Not really sure.

slow texture render first time

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