how can I use animation in cocos2d ?

Question

hello, I am trying to develop a Roulette game for iPhone. How can I animation (spin) the Roulette board?

Answer 1

I have no idea how to do this in cocos2d (or even what that is), but you can do this using Core Animation either with CALayers or UIViews. Probably the simplest way would be to create a UIImageView containing an image of your roulette wheel and animate that.

To accomplish this, first set up your UIImageView by initializing it with your roulette wheel image. When you want the wheel to spin, use the following code:

CATransform3D rotationTransform = CATransform3DMakeRotation(1.0f * M_PI, 0, 0, 1.0);

CABasicAnimation* rotationAnimation;
rotationAnimation = [CABasicAnimation animationWithKeyPath:@"transform"];

rotationAnimation.toValue = [NSValue valueWithCATransform3D:rotationTransform];
rotationAnimation.duration = 0.25f;
rotationAnimation.cumulative = YES;
rotationAnimation.repeatCount = 10; 

[rotatingImage.layer addAnimation:rotationAnimation forKey:@"rotationAnimation"];

assuming that rotatingImage is your UIImageView.

In this example, the wheel would rotate 5 times, with each rotation taking 0.5 seconds. The rotations are split in half because Core Animation will go to the next closest state, so the most you can rotate something is a half rotation before the animation wants to rotate in the other direction. That is, the pi radian (180 degree) rotation here goes a half-circle, but if you used (1.5f * pi) for your rotation angle, it would only go a quarter-circle. Likewise, if you used (0.999f * pi), the circle would rotate in a clockwise manner.

You'll want to implement acceleration and deceleration of your wheel, and for those a CAKeyframeAnimation would take the place of the CABasicAnimation in this example.

Answer 2

There are a couple of ways you can do it.

If you have the frame-by-frame animation for the wheel, check out AtlasDemo (part of cocos2d distribution).

Otherwise, take a look at Sprite's RotateBy: method.

Answer 3

It's quite simple in Cocos2D:

[sprite runAction:[RotateBy actionWithDuration:dur angle:360]];

to make one turn or

id action = [RepeatForever actionWithAction: [RotateBy actionWithDuration:dur angle:360]];
[sprite runAction:action];

and

[sprite stopAction:action];

if you need to rotate continuously.

Don't forget to make sure that sprite transformAnchor is set to center of the image. And I guess next question should arise - how to make it stop smoothly ;)

More on actions: http://lethain.com/entry/2008/oct/03/notes-on-cocos2d-iphone-development (it's for older version, so it uses deprecated 'do' instead of 'runAction')

Answer 4

You can rotate a view, by some number of radians, regardless of whether it is less than a full rotation or many multiples of a full rotation, without having to split the rotation into pieces. As an example, the following code will spin a view, once per second, for a specified number of seconds. You can easily modify it to spin a view by a certain number of rotations, or by some number of radians.

- (void) runSpinAnimationWithDuration:(CGFloat) duration;
{
    CABasicAnimation* rotationAnimation;
    rotationAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation.z"];
    rotationAnimation.toValue = [NSNumber numberWithFloat: M_PI * 2.0 /* full rotation*/ * rotations * duration ];
    rotationAnimation.duration = duration;
    rotationAnimation.cumulative = YES;
    rotationAnimation.repeatCount = 1.0; 
    rotationAnimation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];

    [myView.layer addAnimation:rotationAnimation forKey:@"rotationAnimation"];
}