Question

My problem: I have created a parent sprite which rotates forever. I have created a child sprite to it which I want to move along with the parent sprite but not rotate it. My scenario exactly is that the parent sprite is a windmill and I am rotating it, but the child sprite is a bucket at the end of one windmill bar. So when the windmill rotates, I want the bucket to just move in that motion, where as now its moving and also rotating which looks unrealistic.

Here is the code:

CGSize winSize = [CCDirector sharedDirector].winSize;

windmill = [CCSprite spriteWithFile:@"Chorki.png"];
windmill.position = CGPointMake(winSize.width*0.02f, winSize.height*0.56f);
windmill.scale = 0.55f;
[self addChild:windmill z:0];
//Add windmill sprite on screen

CCRotateBy *rot = [CCRepeatForever actionWithAction:[CCRotateBy actionWithDuration:5 angle: 360]];
    [windmill runAction:rot];
//The above code to rotate windmill, the next code is to add child sprite of bucket

CCSprite *bucket1 =  [CCSprite spriteWithFile:@"BucketBug.png"];
bucket1.position = ccp(235, 490.2f);
[windmill addChild:bucket1 z:-1]; 

EDIT 1:

Sorry I forgot to show the code to rotate the sprite. Now its added.

Answer 1

Take a look at the ccHonorParentTransform enum:

/**
 Whether or not an CCSprite will rotate, scale or translate with it's parent.
 Useful in health bars, when you want that the health bar translates with it's parent but you don't
 want it to rotate with its parent.
 @since v0.99.0
 */
typedef enum {
    //! Translate with it's parent
    CC_HONOR_PARENT_TRANSFORM_TRANSLATE =  1 << 0,
    //! Rotate with it's parent
    CC_HONOR_PARENT_TRANSFORM_ROTATE    =  1 << 1,
    //! Scale with it's parent
    CC_HONOR_PARENT_TRANSFORM_SCALE     =  1 << 2,
    //! Skew with it's parent
    CC_HONOR_PARENT_TRANSFORM_SKEW      =  1 << 3,

    //! All possible transformation enabled. Default value.
    CC_HONOR_PARENT_TRANSFORM_ALL       =  CC_HONOR_PARENT_TRANSFORM_TRANSLATE | CC_HONOR_PARENT_TRANSFORM_ROTATE | CC_HONOR_PARENT_TRANSFORM_SCALE | CC_HONOR_PARENT_TRANSFORM_SKEW,

} ccHonorParentTransform;

It is set through the following property of CCNode:

/** whether or not to transform according to its parent transfomrations.
 Useful for health bars. eg: Don't rotate the health bar, even if the parent rotates.
 IMPORTANT: Only valid if it is rendered using an CCSpriteBatchNode.
 @since v0.99.0
 */
@property (nonatomic,readwrite) ccHonorParentTransform honorParentTransform;

Note that this will only work if the sprites are in a CCSpriteBatchNode. Since mine was not, I decided to let the parent node update the child node by settings the rotation of the child equal to the opposite of its own rotation, thus keeping the child’s rotation relative to the world constant.

// In a scheduled update function of the parent, see CCNode header for schedule functions
bucket.rotation = -self.rotation;