Facebook open-sources ‘Pop’, the animation framework that drives the visual effects in Paper


Facebook has open-sourced a lot of stuff recently, but this is what most developers have been waiting for. Developed originally at Push Pop Press, and refined by Facebook, the company has today released its Pop animation framework publicly. Developers can check out the code from the GitHub repository.

The library enables rapid development of rich animations for iOS (and Mac) apps. Although Core Animation, (Apple’s built-in framework) is well suited to fire-and-forget animations, Pop was created to work seamlessly with modern interactive physics-centric user interfaces.

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Although the specifics are rather technical, the framework differs fundamentally from Core Animation by working  on the basis of always converging towards a final (malleable) value, which is much more flexible. The springiness and bounciness seen universally in iOS 7 apps nowadays is also built in to the core of the framework.

Developers can use Pop across their application, from adding visual flair to button states to full screen animated transitions and much more. In many ways, Pop offers the functionality that Apple should be offering natively, if it wants to help developers modernize their app’s experiences.

Pop powers all of the animations seen in the widely-praised Facebook app. There’s a lot of behind-the-scenes engineering that took place to create these effects, so developers wanting to replicate some of Paper’s finesse should definitely take a look at Pop.

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  1. Jon Heckman - 9 years ago

    So its awesome that more stuff is open sourced but… “widely-praised Facebook app” your kidding right?
    The entire app is an abomination. Insanely slow (at least its better then the HTML one) and doesn’t work half the time. Plus they can’t settle on a design for anything for more then a patch or 2.

    • Greg Kaplan (@kaplag) - 9 years ago

      “There’s a lot of behind-the-scenes engineering that took place to create these effects, so developers wanting to replicate some of Paper’s finesse should definitely”

      – the sentence after the one you quoted.

      I think they might be referring to Paper and using Facebook as the brand name. I don’t know.

    • Ry L - 9 years ago

      That is meant to reference Facebook’s “Paper” app. The normal one sucks. Paper is pretty slick and full of animations.

  2. Yes (@AMillah) - 9 years ago

    “Pop offers the functionality Apple should be offering natively”

    I’m no expert, but doesn’t the newly introduced UIKit Dynamics in iOS 7 do exactly that? I would be interested to see how the two frameworks compare. The Paper app uses a lot of physics-based interactions that UIKit Dynamics can similarly do, like the springy behavior in the swipe back gesture in the settings menu being similar to the springy-ness in Messages scrolling. The only animation in Paper I’ve seen that I think is an improvement over the standard system animation is the rotate animation, in Paper it has a subtle bounce when it completes rotating. Obviously Paper does some other things that system apps don’t do, like pulling down on the notifications panel creates an elastic effect where it sort of pulls on the window and then detaches when you pull it past the breaking point.

    Really neat stuff, so I’d love to see how it compared to UIKit Dynamics. Or maybe they’re completely different things and I don’t know what I’m talking about ;)


Avatar for Benjamin Mayo Benjamin Mayo

Benjamin develops iOS apps professionally and covers Apple news and rumors for 9to5Mac. Listen to Benjamin, every week, on the Happy Hour podcast. Check out his personal blog. Message Benjamin over email or Twitter.