I'm standing at the front of a darkened room full of middle-school girls, telling them about user interface patterns and trying to get them excited about reading Apple's iOS Human Interface Guidelines.
It's going better than I'd thought—on the whole, they're pretty attentive. I guess that's the kind of girl who signs up for a week-long summer camp about iOS development. Then I arrive at my single slide about the upcoming changes to the platform (they'll be working in iOS 6 this week, so I don't want to bombard them with the monumental shift in form that is the iOS 7 beta). Suddenly a hand shoots up.
"Why did they DO that?"
I do my best to answer, but leave thinking I owe them a fuller explanation and more analysis. So here goes:
From faux 3D to real 2.5D
According to Apple, the crux of iOS 7 is emphasizing the user's content by doing away with ornamentation, but iOS has always been about giving the user's content top priority in every app—that's been one of the main tenets of its human interface principles since its inception.
This used to mean using rich, photo-realistic details and analog metaphors to help users intuit how to use an app, allowing them to access their content or accomplish their task as quickly and easily as possible. But visual cues that once helped us understand how to interact with a brand-new type of device have grown cumbersome and stale as we've grown more and more accustomed to using these devices. The subsequent stripping away of artifice and ornamentation in iOS 7 hasn't actually changed many interface patterns; it's merely removed unnecessary distraction.
In shedding this faux-3D skin, iOS has transformed into something remarkable, with a new kind of depth and motion. Apple has given up the artificial 3D image techniques of deep shadows, strong highlights, and gloss in favor of relying on spry animation and the parallax effects of flat planes to convey the sensation of depth. Developer Manton Reece compared it to multiplane camera technology. In my former life at an animation studio, I called it "two-and-a-half-D" (2.5D), but it's the same idea: Using AfterEffects, I'd set backgrounds and images on different planes on the z-axis, and animate a virtual camera to move through and around them. The planes could never look fully three-dimensional, but the parallax and depth-of-field effects were far more compelling and lifelike than simply moving an image from left to right.
iOS 7 harnesses 2.5D and uses it to enhance your sensation of depth. The faux 3D effects used in previous versions of iOS would clash here, rendering the illusion of space less effective. Simply tilting the phone hints subtly at where elements exist in relation to each other and to the background. Moving through the interface from home screen to folder to app feels like the short film Powers of 10, or like falling into Mary Poppins' carpet bag. It is larger than it first appears, and the effect is delightful.
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