Loading textures in the background?

[bluelobster]

So I am trying to do something that is not new or revolutionary...display a progress bar during the loading of my levels.

To do this I spawn a new thread to do all the loading, while the main thread draws the progress bar...seems like it should work huh?

Nope!

When I go to render my world I get nothing but white...

If I do everything in the main thread (which of course doesn't allow the progress bar to work) everything renders fine.

So my question is wtf?!

I've been looking at this for the last two days and am really at my wit's end.

I was thinking that maybe because I am loading my textures in a different thread only that thread would know about them...so I created a singleton object to hold all my textures...so shouldn't matter what thread is populating it...since it's a singleton...it should be available to everyone? I mean the next thread (the main thread) that grabs it should get the correct data...right?

During debugging I can inspect all my texture objects and sure enough everything is there...name, image name, texture coords, verts, etc... But sadly only white is displayed =(

Anyone know what's going on here?

Thank you for your time.

[georgeburns]

Originally Posted by bluelobster

To do this I spawn a new thread to do all the loading, while the main thread draws the progress bar...seems like it should work huh?

What happens when you load in the main thread and do the progress bar in the new thread?

[bluelobster]

Good question.

Maybe I don't understand how threads work but here is what I understand needs to happen...

For the progress bar:

// level load
- (void) loadLevel
{
  // do some stuff
  
  // update percentDone

  // do more stuff

  // update percentDone
}

// render
- (void) render
{
  // figure out the bar length
  barLength = barLength * percentDone;
  // render the bar
  renderBar();
}

So the problem here is the core of the progress bar update is done in the render loop...I don't know that a thread that is created would be able to access the render loop since it is setup and called from the grand daddy game loop. Know what I mean?

Is it possible to render stuff in a separate thread? I don't know how to do that...

What's nice about what i'm doing now...well not that nice because it doesn't work...but I can let my main game loop go rendering the frames as it does and when I spawn off the thread to do the loading work it doesn't have to worry about being involved with the renderer...

[georgeburns]

Originally Posted by bluelobster

Good question.

Maybe I don't understand how threads work but here is what I understand needs to happen...

For the progress bar:

// level load
- (void) loadLevel
{
  // do some stuff
  
  // update percentDone

  // do more stuff

  // update percentDone
}

// render
- (void) render
{
  // figure out the bar length
  barLength = barLength * percentDone;
  // render the bar
  renderBar();
}

So the problem here is the core of the progress bar update is done in the render loop...I don't know that a thread that is created would be able to access the render loop since it is setup and called from the grand daddy game loop. Know what I mean?

Is it possible to render stuff in a separate thread? I don't know how to do that...

What's nice about what i'm doing now...well not that nice because it doesn't work...but I can let my main game loop go rendering the frames as it does and when I spawn off the thread to do the loading work it doesn't have to worry about being involved with the renderer...

I'm not seeing any code for the threading.

[bluelobster]

Originally Posted by georgeburns

I'm not seeing any code for the threading.

Oh here you go...

- (void) spawnThread
{
  [NSThread detachNewThreadSelector:@selector(loadLevel) toTarget:self withObject:nil];
}

// level load
- (void) loadLevel
{
  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

  // do some stuff
  
  // update shared variable
  percentDone += x;

  // do more stuff

  // update percentDone
  percentDone += x;

  [pool release];
}

// render
- (void) render
{
  // figure out the bar length
  barLength = barLength * percentDone;
  // render the bar
  [bar render];

  // render rest of the scene
}

[bluelobster]

Hmmm I think I may have found the problem...

It seems this thread I am spawning off may not have an OpenGL context?


*Edit* it has an opengl context but doesn't have the same one the main thread is use...