Problem with smoke bubble in cocos2d.

Question

I am having a problem. When the smokeMoveBy action starts a small smoke bubble is spotted on the screen at other place then the moving path of the smoke. This is only happening when I am using scaleX and scaleY. The method smokeLoop is being called at each 1 seconds in the scheduler. Here self is a layer.

Any solutions?

My code follows,

CGPoint dummyPosition=ccp(600, 600);
ParticleSystem *smoke = [ParticleSmoke node];
ccColor4F startColor;
startColor.r = 1.f;
startColor.g = 1.f;
startColor.b = 1.f;
startColor.a = 1.f;
[smoke setStartColor:startColor];
ccColor4F endColor;
endColor.r = 0.8f;
endColor.g = 0.8f;
endColor.b = 0.8f;
endColor.a = 1.0f;
[smoke setEndColor:endColor];
[smoke setLife:0.1f];
[smoke setScaleX:0.1f];
[smoke setScaleY:0.2f];
[smoke setStartSize:30.f];
[self addChild:smoke z:2];
[smoke setPosition:dummyPosition];

-(void)smokeLoop{
id smokeMoveBy = [MoveBy actionWithDuration:durTime position:ccp(0.f, (-1.f*480))]];
id smokeSeq=[Sequence actions:[Place actionWithPosition:smokeInitPosition], smokeMoveBy, nil];
[smoke runAction:smokeSeq];
}

Answer 1

Not sure if this is your issue, but I had an issue with Cocos2D, scaling and moving, which I solved with moving the anchorPoint.

What I wanted to do is zoom (scale) and move a layer. Zooming would move fine if position was {0,0} and transform point was {0.5,0.5}. But then if I'd move it, it would still transform around {0.5,0.5}, which might by then be out of screen, so it would scale really weird.

Solution was to move the transform point to the middle of the screen, every time I moved the layer's position. This was not an easy formula for me to fix, as when I moved the transform point, the scale operation would have a new center point.

The formula I ended up using was the following:

layer = self.foreground;
ccpAdd(
    ccpDivide(
        ccpNeg(layer.position),
        (CGPoint){layer.contentSize.width, layer.contentSize.height}),
    (CGPoint){0.5f,0.5f}
);

Basically: Divide the inverse of the layers position (meaning, {300,200} would become {-300,-200}) by the size of the layer {480,320}, and then add {0.5,0.5} (as I want my anchor to be always center + offset)

Anyway, you may need to work out a completely different formula, but this worked for me. I had to apply this to my anchor point every time I moved the layer.

Good luck, hope this helps!