# ARPen: Mid-Air Interactions

> Draw and model in mid-air with marker or custom Bluetooth pen. (iPhone/iPad app by RWTH Aachen University.)

- Source: https://appshunter.io/ios/app/arpen-mid-air-interactions/id1459493311 (this page in markdown: same URL + `.md`)
- Developer: [RWTH Aachen University](https://appshunter.io/developer/371466796)
- Category: Productivity, Entertainment
- Price: Free
- Rating: 2.50/5 from 2 App Store ratings · 2 written reviews indexed
- Age rating: 4+
- Requires: iOS 14.2 · 55 MB
- Languages: American English
- Released: 2019-04-27
- Data updated: 2026-08-14
- Monetization: free
- User reviews in markdown: https://appshunter.io/ios/app/arpen-mid-air-interactions/id1459493311/reviews.md

## What is ARPen?

The ARPen application enables you to draw in mid-air.
By tracking a marker, lines can be created that keep their position in the real world. 

Printing out a marker is all that is needed to test out this interaction. Or you can build a custom Bluetooth pen to have more options. The pen can be built using simple electronic components and machinery in your local Fab Lab. Detailed instructions are available at http://hci.ac/arpen-ios.

With this app you can:
- paint freehand in mid-air
- create simple geometry shapes like cubes
- create complex geometries using sweeps, lofts, revolutions, and merge&intersect operations
- explore techniques for moving, rotating, and scaling objects in mid-air
- explore different menu techniques
- explore depth visualization techniques to show the position of the pen tip relative to other objects in the scene
- export the sketch or model as an *.STL file

This application is part of the Personal Photonics project, which is funded by the German Federal Ministry of Education and Research (BMBF) as part of their Open Photonics call. For more information, visit https://hci.rwth-aachen.de/arpen

## Key features

- Draw freehand in mid-air
- Create simple and complex geometries
- Manipulate objects in 3D space
- Explore depth visualization
- Export models as STL files
- Use marker or custom Bluetooth pen

## Recent user reviews (2 of 2)

All indexed reviews: https://appshunter.io/ios/app/arpen-mid-air-interactions/id1459493311/reviews.md

### 1/5 — Useless

*2020-03-19*

There is no possible way to use this without the specific pen, but it gives you no information on where you can get it or make it, not even a printout! This app is a complete waste of storage.

### 5/5 — Wow this is awesome research

*2019-04-29*

Looking forward to see that at CHI 2019

## Frequently asked questions about ARPen

### How do I start using ARPen to draw in mid-air?

To begin, you'll need to print out a marker. The ARPen application then tracks this marker to create lines that maintain their position in the real world, allowing you to draw in mid-air.

### Can I create complex 3D shapes with ARPen?

Yes, ARPen supports the creation of complex geometries. You can utilize techniques like sweeps, lofts, revolutions, and merge & intersect operations to build intricate 3D models.

### What devices does ARPen support?

ARPen is currently supported on iPhone and iPod devices. It was last updated on March 6, 2021, with version 2.1.

### Can I export my ARPen creations?

Yes, you can export your sketches or models created with ARPen. The application allows you to export your work as an *.STL file, which is a common format for 3D printing.

### Does ARPen have ads?

No, ARPen does not contain advertisements. The application is free to use and does not feature any in-app purchases.

### What is the age rating for ARPen?

ARPen has an age rating of 4+. This indicates it is suitable for users aged four and older.

### Where can I find instructions for building a custom Bluetooth pen for ARPen?

Detailed instructions for building a custom Bluetooth pen are available at http://hci.ac/arpen-ios. This allows for more advanced interaction options beyond using a printed marker.

### What is the user sentiment for ARPen based on ratings?

ARPen has received a rating of 2.5 stars from 2 ratings. This suggests a mixed to negative user reception based on the limited feedback available.

## Version history (last 5 releases)

### 2.1 — 2021-03-06

It is now possible to move, rotate, and scale the objects in the scene. You can combine them by merging or cutting. We have also added more experimental rotation and scaling techniques.

### 2.0 — 2020-10-02

This update adds many new interaction techniques to the ARPen. Besides simple geometries, you can now create more complex geometries by defining paths and shaping them into models using sweeps, revolutions, and boolean operations. Also, there are different menu techniques and depth visualizations to explore.

### 1.2.1 — 2019-10-02

ARPen now also runs on devices with iOS 13.

### 1.1 — 2019-06-19

- You can now create three new geometries: Sphere, Cylinder, and Pyramid.
- When you select a plugin, instructions are provided to help you get started.
- The look & feel of the app has been redesigned—new vibrant color for the UI and drawing, new plugin icons, translucent background for plugin buttons to make them more readable, etc.
- If you make a mistake in your sketch, you can now undo!

### 1.0 — 2019-04-26

No release notes.

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All apps by RWTH Aachen University: https://appshunter.io/developer/371466796

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-14.*