MOTION INK

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  Three real gestures become three distinct light sculptures with Neon, Ember, and Aurora.

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  Creating a Neon light sculpture in camera-free Demo Mode.

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  A finished gesture displayed as a crisp Neon light sculpture.

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  Ember transforms movement into warm light with glowing particle accents.

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  Aurora varies color and width to create an atmospheric light sculpture.

Inspiration

Most drawing apps begin with a screen. MOTION INK began with a different question: what if a physical movement could become something you can see, keep, and share?

What it does

MOTION INK turns an iPhone into a pen for the air. Hold Draw, move the phone, and transform a physical gesture into a luminous sculpture. When the gesture is complete, the camera view gives way to a dark exhibition where the movement is presented as a slowly rotating artwork.

Anyone can draw with the free Neon brush, save artwork locally, and export a vertical replay. MOTION INK Pro adds the Ember and Aurora brushes, 1080p exports, and watermark-free sharing.

How I built it

MOTION INK is built for iPhone with Swift and SwiftUI. ARKit tracks the phone’s movement, while RealityKit turns sampled motion points into glowing 3D trails. Finished artwork is saved locally and can be exported as a still image or a six-second vertical video.

RevenueCat powers monthly and annual subscriptions that unlock the pro entitlement. Customer information controls access to premium brushes and export options, while purchase restoration is available inside the app. No account or custom purchase backend is required.

Challenges

The main challenge was turning noisy device movement into a trail that feels smooth and expressive without allowing geometry or memory usage to grow without limits. I also needed to transition from the live camera view into a readable, centered sculpture and ensure that exported media never includes the camera image.

The app includes a camera-free Demo Mode, VoiceOver support, and a Reduce Motion experience so the core interaction remains accessible.

What I learned

I learned that a simple physical gesture can become an intuitive creative interface when the surrounding UI stays out of the way. I also learned how important graceful fallbacks are when combining AR tracking, media export, and in-app purchases in one experience.

MOTION INK keeps monetization at the edge of creation: everyone can complete and save their first sculpture, while Pro expands the available brushes and export quality.

Built With

• arkit
• avfoundation
• coregraphics
• ios
• realitykit
• revenuecat
• swift
• swiftui
• xcode