In my cocos2d-iphone game, I have 2 backgrounds (CCnodes), each containing a quite complex hierarchy of sprites.

I would like to make a smooth transition between them:

• initially, only the first background is visible
• at the end, only the second one is visible

Is there a good way to set the opacity of a full hierarchy of sprites ?

I tried to recursively set the opacity of all the contained sprites. It kinda works except that:

• i guess it's not very efficient
• i would like the opacity of overlapping sprites to be 'merged' (as if the background was one single big sprite)