iPhone memory usage increases when pushing an EAGL-View using UINavigationController

Question

I am working on a simple iOS game and I am having a problem with UINavigationController and an EAGL-View. The situation is as follows: I use one EAGL-View in conjunction with multiple controllers. Whenever I push the MainViewController (which does all the custom openGL drawing), I end up using more memory (around 5MB per push!).

The problem seems to be within [eaglView_ setFramebuffer] - or at least that's where almost all allocations seem to happen (I've checked the live bytes via Instruments - around 70% of memory is allocated in this function).

EAGLView::setFramebuffer:

- (void)setFramebuffer {
    if (context) {
        [EAGLContext setCurrentContext:context];

        if (!defaultFramebuffer)
             [self createFramebuffer];

        glBindFramebuffer(GL_FRAMEBUFFER, defaultFramebuffer);
        glBindFramebuffer(GL_FRAMEBUFFER, msaaFramebuffer);         
        glViewport(0, 0, framebufferWidth, framebufferHeight);
    }
}

and EAGLView::createFramebuffer:

- (void)createFramebuffer
{
    if (context && !defaultFramebuffer) {
        [EAGLContext setCurrentContext:context];

        // Create default framebuffer object.
        glGenFramebuffers(1, &defaultFramebuffer);
        glBindFramebuffer(GL_FRAMEBUFFER, defaultFramebuffer);

        // Create color render buffer and allocate backing store.
        glGenRenderbuffers(1, &colorRenderbuffer);
        glBindRenderbuffer(GL_RENDERBUFFER, colorRenderbuffer);
        [context renderbufferStorage:GL_RENDERBUFFER fromDrawable:(CAEAGLLayer *)self.layer];
        glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &framebufferWidth);
        glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, &framebufferHeight);

        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, colorRenderbuffer);

        //MSAA stuff
        glGenFramebuffers(1, &msaaFramebuffer);
        glGenRenderbuffers(1, &msaaRenderBuffer);
        glBindFramebuffer(GL_FRAMEBUFFER, msaaFramebuffer);
        glBindRenderbuffer(GL_RENDERBUFFER, msaaRenderBuffer);

        glRenderbufferStorageMultisampleAPPLE(GL_RENDERBUFFER, 4, GL_RGBA8_OES, framebufferWidth, framebufferHeight);
        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, msaaRenderBuffer);

        glGenRenderbuffers(1, &msaaDepthBuffer);      
        glBindRenderbuffer(GL_RENDERBUFFER, msaaDepthBuffer);
        glRenderbufferStorageMultisampleAPPLE(GL_RENDERBUFFER, 4, GL_DEPTH_COMPONENT16, framebufferWidth, framebufferHeight);
        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, msaaDepthBuffer);

        if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
            NSLog(@"Failed to make complete framebuffer object %x", glCheckFramebufferStatus(GL_FRAMEBUFFER));

    }
}

As you can see - nothing special there. I switch my ViewControllers like this: (in the AppDelegate)

- (void) swichToViewController: (UIViewController*) newViewController overlapCurrentView: (bool) overlap {
  // get the viewController on top of the stack - popViewController doesn't do anything if it's the rootViewController.
  if(!overlap) {
    // clear everything that was on the eaglView before 
    [eaglView_ clearFramebuffer];
    [eaglView_ applyMSAA];
    [eaglView_ presentFramebuffer];         
  }

  UIViewController* oldViewController = [navController_ topViewController];
  // see if the view to be switched to is already the top controller:
  if(oldViewController == newViewController)
    return;
  // if the view is already on the stack, just remove all views on top of it:
  if([[navController_ viewControllers] containsObject:newViewController]) {
    [oldViewController setView:nil];
    [newViewController setView:eaglView_];
    [navController_ popToViewController:newViewController animated:!overlap];
    return;
  }
  // else push the new controller
  [navController_ popViewControllerAnimated:NO];
  [oldViewController setView:nil];
  [newViewController setView:eaglView_];
  [navController_ pushViewController:newViewController animated:!overlap];
}

Finally, I render my sprites like this: (In my MainViewController.mm):

- (void)drawFrame
{
  // When I delete this line, I just get a white screen, even if I have called setFramebuffer earlier(?!)
  [(EAGLView *)self.view setFramebuffer];

  glClearColor(1, 1, 1, 1);
  glClear(GL_COLOR_BUFFER_BIT); 

  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();


  GLfloat screenWidth = [UIScreen mainScreen].bounds.size.width;
  GLfloat screenHeight = [UIScreen mainScreen].bounds.size.height;

  glOrthof(0, screenWidth, 0, screenHeight, -1.0, 1.0);
  glViewport(0, 0, screenWidth, screenHeight);

  [gameManager_ playGame];


  //MSAA stuff
  [(EAGLView *)self.view applyMSAA];

  [(EAGLView *)self.view presentFramebuffer];
  [(EAGLView *)self.view clearFramebuffer];
}

Something that might be worth mentioning is that I don't allocate the views every time I push them, I keep references to them until the game exits.

[gameManager_ playGame] draws the sprites to the screen - but I've used this method in another project without any memory problems.

Any help would be really appreciated as I've been stuck on this for 2 days :/

Edit: I've been able to narrow the problem down to a call to gldLoadFramebuffer. This is called whenever I try to draw something on the screen using an openGL function. It seems to consume more memory when the context changes... But how could I avoid that?

Answer 1

I think I found the problem. For anyone interested: The MSAA-Buffers weren't correctly deleted on switching the views. That caused the performance to drop significantly after a few pushes, and was also responsible for the increase in memory usage.