Game Loop with CADisplayLink

[samurle]

I have a very simple game loop driven by CADisplayLink. It basically moves a single UIImageView
across screen at a constant rate by updating its position. However, the movement is somewhat jerky.

I'm using the default FrameInterval value of 1 for 60fps. And the image does use transparency.

Just wondering what I can do to improve it. Changing the project to release mode doesn't help.

I tried using a constant delta time of 1/60, and also tried calculating my own delta time,
but that doesn't seem to help either. It doesn't make any difference.

 displayLink = [NSClassFromString(@"CADisplayLink") displayLinkWithTarget:self selector:@selector(myGameLoop:)];
 [displayLink setFrameInterval:1];
 [displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];

-(void)myGameLoop {

 for(Piece *piece in self.pieces) {
   float speed = dt * piece.speed;
   piece.center += CGPointMake( dx * speed, dy * speed );
 }
}

Any suggestions?

[Duncan C]

Originally Posted by samurle

I have a very simple game loop driven by CADisplayLink. It basically moves a single UIImageView
across screen at a constant rate by updating its position. However, the movement is somewhat jerky.

I'm using the default FrameInterval value of 1 for 60fps. And the image does use transparency.

Just wondering what I can do to improve it. Changing the project to release mode doesn't help.

I tried using a constant delta time of 1/60, and also tried calculating my own delta time,
but that doesn't seem to help either. It doesn't make any difference.

 displayLink = [NSClassFromString(@"CADisplayLink") displayLinkWithTarget:self selector:@selector(myGameLoop:)];
 [displayLink setFrameInterval:1];
 [displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];

-(void)myGameLoop {

 for(Piece *piece in self.pieces) {
   float speed = dt * piece.speed;
   piece.center += CGPointMake( dx * speed, dy * speed );
 }
}

Any suggestions?

Use a completely different approach. Re-rendering a view by moving it's location for every frame does not make good use of the graphics hardware.

For view-based animation, you should use Core Animation, and let the system do the rendering.

For frame-based animation like you're trying to do, use OpenGL or a framework like Cocos2D.

[samurle]

Originally Posted by Duncan C

Use a completely different approach. Re-rendering a view by moving it's location for every frame does not make good use of the graphics hardware.

For view-based animation, you should use Core Animation, and let the system do the rendering.

For frame-based animation like you're trying to do, use OpenGL or a framework like Cocos2D.

Thanks, what type of timing mechanism does Cocos2D use? I see it has a class called CCScheduler.h,
but I'm not sure how it gets fired.

I don't see any mention of CADisplayLink or NSTimer.
Then again, I think it does use CADisplayLink too.

[Duncan C]

Originally Posted by samurle

Thanks, what type of timing mechanism does Cocos2D use? I see it has a class called CCScheduler.h,
but I'm not sure how it gets fired.

I don't see any mention of CADisplayLink or NSTimer.
Then again, I think it does use CADisplayLink too.

No idea. Never used it.