Facebook is making available to developers the engine responsible for the impressive animations used for Paper, a personalized magazine app launched by Facebook in January.
Aside from its ability to filter out noise from the personal news feed, one of Paper's standard features is the smooth, card-based animations and transitions that come with the user's every swipe. This is all thanks to Pop, an aptly named animation engine developed by Push Pop Press, a maker of interactive e-books acquired by Facebook in 2011.
"When I co-founded Push Pop Press in 2010, our goal was to create a realistic, physics-everywhere experience," writes Kimon Tsinteris, who now works as a software engineer for Facebook.
"We wanted a solution that would allow us to evoke the same delightful experience of UIScrollView throughout the whole application. Pop is the latest manifestation of that vision, allowing us to keep the familiar and powerful programming model of Core Animation while also capturing a gesture's velocity and better reflecting user intent," he adds.
Aside from using traditional static animations, Pop leverages dynamic animations to control the scrolling, bouncing and unfolding effects on the personal newspaper app. Pop hopes to make animation convenient for developers by adding "Spring," "Decay" and "Custom" animations to the four static ones: "linear," "ease-in," "ease-out" and "ease-in-ease-out."
"Spring" is a bouncy animation similar to that used in Paper, while "Decay" brings whatever movement to an eventual halt, depending on the user's movements. Both use velocity as an input, which means the animations respond to the user's gestures.
"The innovation of touch surfaces has ushered a new wave of software design. Direct manipulation of onscreen elements has removed one level of indirection, which in turn has raised our expectations for the screen as a medium. If objects respond to our touches, they should also respond to the velocity of our flick," Tsinteris writes.
Pop is an "extensible framework" that allows developers to build upon the existing code to integrate their own codes and create unique animation effects. It is developer-friendly, writes Tsinteris, as it is modeled after the interface of Apple's Core Animation.
Before Pop, Facebook has released a number of open-source products. The growing list includes the Open Compute project, the Tornado Python web framework and HipHop Virtual Machine (HHVM). KVOController, Shimmer and Tweaks are also some of Facebook's open-source tools for iOS.
Paper is currently only available for iPhone users. During Facebook's first-quarter conference call which reported stellar revenue coming from mobile ads, company executives hailed Paper a success, although without dropping specific figures. With better figures clocking in from its mobile division, Facebook is expected to set its sights largely on mobile.
