I started working on Layers for iPad the morning apple released the iPad SDK. I’d been looking forward to the release of the iPad for months, and it made sense to make a dedicated version of the app. I’d always had a difficult time drawing on the iPhone’s small 3″ screen. The iPad seemed like a perfect tool for professional artists–a digital sketch book you could carry anywhere.
The iPad’s larger form factor also raised new interaction questions. It was too big to shake, so the “wrist flick”-triggered menus in the original Layers app were out. It had more room for contextual information-toolbars wouldn’t significantly limit the size of the canvas viewport. The iPad also created new opportunities for community. It’s large screen was so good for showing off art that it seemed natural to allow people to post paintings and browse and comment on others work within the app. From the earliest phase of design, the focus was on building a community around the art people created on the iPad.
I spent about three weeks designing an interface for the iPad app, prototyping and fleshing out different screens of the app in Fireworks. Since I knew I would be doing the entire app myself, I didn’t bother creating storyboards using the individual interface mockups.
I like to write code during the design phase when I work on personal projects: a few hours of design, a few hours of code, repeat. It helps to step away from the designs every few hours. I started moving code from the iPhone version of Layers over to the iPad on day one, and a couple big issues became obvious in the first few weeks:
1. The display / memory ratio on the iPad makes it hard to keep display-quality images in memory. The iPhone version of Layers kept six 512×512 OpenGL textures in memory, but the iPad version isn’t able to keep six 1024×1024 images in memory. Fail!
2. Saving the image for each layer took more time (roughly 4x more, since there were 4x as many pixels) and caused the app to be terminated early when sent to the background.
3. Some procedures in Layers, like undoing a “Shift Layer” operation, took too much memory when the images were scaled up.
Unfortunately, I didn’t have early access to iPad hardware, so I didn’t know that #1 and #3 would be an issue until the app was actually live on the store. I got a ton of emails the week the iPad went on sale, and I skipped an entire week of class to fix the problems. The solution was a much smarter method of memory management that allows layers and parts of the undo stack to be paged to disk when the app receives memory warnings. It brought some major speed improvements to the iPad version, and I’ve since been rolled it back into the iPhone version.
Layers for iPad consists of 22,000 lines of Objective-C code, about 10,000 of which are shared with the iPhone version. The community component of the app is built in PHP and mySQL, and uses HTML5 and advanced Safari CSS 3 markup to create a convincing and “native” experience within the app. My experience building the community website was very positive. CSS 3 support on the iPad is great, I think web views are the best way to deliver native-looking and richly customized interfaces. You can even specify your own fonts. It’s beautifully fast. Had I chosen to deliver content via XML and render it all in custom UIViews, there’s no way I could have completed the app in three months.
In the first six months after its release, Layers for iPad was downloaded about 10,500 times. The Layers Gallery, the community built around content generated in the app, hosts thousands of paintings. The app was featured on the front page of the App Store during the week of April 28th, and was reviewed by TUAW and MacWorld twice! It was featured in Incase’s 2010 advertising campaign and billed as the favorite painting app of Ron Radziner. The Layers for iPad website has also received recognition for its clean, refined design on OneExtraPixel”, Designer Daily and Web Design Tuts+
After Layers was released for iPad, I worked with MEDLMobile in San Francisco to develop the app “Drawing Step by Step with Walter Foster” using the Layers painting engine to emulate realistic pens and pencils. During it’s first week on the store, that app was ranked #1 in Productivity.