Hey!

I'm in the progress of developing a really nice game for the iPhone/iPod Touch using OpenGL.

As some of you have noticed the game called Labyrinth is experiencing screen flicker sometimes. This is also the case for the game that I'm developing. Do any of you know what could solve this?

To explain the situation:

The game uses the UIGLView by Andrew Willmott (big thanks to him for all work on it!). As in his demo, the screen is updated by an NSTimer calling setNeedsDisplay. If I lower the update interval to 0.5 seconds or so the screen flicker happens only once if any time. With 0.1 it happens more like an occasional blink. I'm thinking that it might have something to do with:

eglWaitNative(EGL_CORE_NATIVE_ENGINE);
CoreSurfaceBufferLock(mScreenSurface, 3);

Thus calling the screen lock in the middle of a system screen update or in other ways colliding with system redraw calls.

The flickering is not apparent in Andrew's full screen app (which is NOT strange as it uses a dedicated screen surface an a non-event driven run loop).

So, what do you think could solve this problem?

Cheers,
Max

Maybe uiview startHeartbeat: sel inRunLoopMode:

Instead of NSTimer for refreshes?

From my MobileMusicPlayer disassembly, heartBeat seems to be used in the coverflow stuff, for what I assume at this stage is redraw related stuff.

Oh, cool. I did actually take a look at just that call, but couldn't find much about it. Do you know how to call it?

Just a question out of curiosity: how do you dissemble something like the music player app?

Cheers,
Max

Dunno if it's what you're after but he's an example:

[myUIView startHeartbeat:@selector(heartbeatCallback inRunLoopMode:nil];

then define the selector method

- (void)heartbeatCallbackid)unused
{
// do stuff here
}

Apparently it's called by the UI occasionally. Other than that, I don't know anything about it.

For disassembly I use ravel-arm, but IDA is another arm disassembler capable of reversing arm mach-o binaries

Great info! I'll try that and report the results!

Cheers,
Max

I did this in the init for the main view, which contains the UIGLView:

Code:

[self startHeartbeat:@selector(update) inRunLoopMode:nil];

And further down in the implementation:

Code:

- (void)update {	
    [glview setNeedsDisplay];
}

This does work and it seems to lock to a frame rate of about 60FPS.

BUT, the flicker is still there. Now it's more even, that is all buttons, status bar and so on blinks at the same time. It also still flickers when the home button is pushed (probably has to catch the button press and call [self stopHeartbeat] to stop the redraw).

To conclude:

- startHeartbeat works
- it does not get rid of the flicker
- it seems to sync up all drawing a bit

Cheers,
Max

I took a slightly different approach, though I'm not sure if it helps the flickering or not. I don't have flickering problems with my app or with labyrinth, so it's possible it's just my setup.

Here are some links to my test app:

http://ixionstudios.com/files/glTest_app.zip
http://ixionstudios.com/files/glTest_app.tar.gz
http://ixionstudios.com/files/glTest_src.zip
http://ixionstudios.com/files/glTest_src.tar.gz


-NSB