Animating scene changes in Sparrow

sick_boy

Hi there, I was wondering if it is possible to animate the transition from one page to another one. More specifically I am deallocating a page sprite to reallocate another one in the same SPStage. What I want to do is to create some animation similar to the ones used by Core Animation when another page comes on the screen. Do I have to animate every single object of the page sprite by myself or is there an easier way?

borrrden

Well, it depends on what kind of transition you want. If a simple slide effect would be ok, then you could setup your sprite offscreen, and slide the master containers for the existing scene and the new scene together (all children will be animated automatically, so there is never any need to go through "every single object").

sick_boy

Ok, thanks this is a good point to start with. What if I would make some more complicated animations, like page curl or stuff like that?

alex_h

Page flip is very complicated and difficult to do in Sparrow, as there is currently no facility to mask objects. When I built a page flip app I had to swap between core graphics code to do the page flip, and Sparrow for the animation on pages between turning. This was pretty hard work, and quite processor intensive. To do a genuine 'page curl' you would need to curl the page in 3 dimensions which wouldn't work with sparrow as it uses a an incompatible mode of camera projection within it's OpenGL code.

sick_boy

Ok, thanks for the explanation!Last question: coming back to the simple slide effect, can I apply the animation directly to the page sprite? I tried to use a tween with target equal to the page sprite and to animate the x property of the sprite, then adding the tween to the juggler, but the sprite doesn't want to move. If I set the x property by code when I build up my sprite, it gets located in the right position, according to the x property. Where am I wrong?

alex_h

You should be able to tween the page sprite using the process you have described.
Might be worth posting your code from where you apply the tween up here for someone to look at, maybe there's a mistake in your x co-ordinates or something?

borrrden

Make sure that you are actually adding to a valid juggler, in certain specific cases [self.stage.juggler] will return nil (If it does, use [SPStage mainStage].juggler instead).

alex_h

that's true - good point! You can only reference the stage from within a sprite once it has been added to the display list, which won't have happened within it's default init method.

sick_boy

You were right guys the problem was with the juggler. Thanks

jdraymon

Has there been any change to how OpenGL works now in sparrow 2, where I might try to implement a page curl? My requirements involve having a sparrow animated figure sitting above the page turn, which kind of rules out involving core graphics