Given all the expectations aroused by 3D printing, a mobile app that captures on your smartphone objects that you want to print out in 3D looks a highly promising idea.

Advanced 3D Scanning Facilities Now Available on Smartphones

In practice 3D scanning means capturing the geometry of the 3D world. This technology does exist, but it follows complicated processes that make it quite hard to use. 3D scanning has therefore not so far been available to the general public, and not been convenient for mobile use. Now however the Computer Vision and Geometry Lab of the Swiss Federal Institute of Technology in Zurich (ETH Zurich) has developed a smartphone app along the lines of the Trimensional 3D scanner, which can scan objects and human faces in 3D and so fill some of the gaps in this area. The difference is that ETH Zurich has achieved far more successful results: scans taken with the app can be visualised, modelled and modified directly on the mobile screen and then printed out using a 3D printer.

Creating a 3D form more or less like taking a photo     

In the same way as you point your phone at your subject when you wish to take a photograph, all you have to is move the phone around the object of interest and, after a few motions, a 3D model appears on the screen. As you continue to move the device, additional images are recorded automatically and used to extend and fill out the captured 3D model. All the calculations are performed directly on the mobile device, so you can obtain immediate feedback and then select additional viewpoints to cover any missing parts of the 3D model. This is a crucial advantage compared with solutions that rely on subsequent batch-processing of all the images in the Cloud. Another useful aspect is that having the solution on your mobile phone means you can use the app anywhere, including in low-light conditions such as inside a museum. A user can therefore capture a 3D model of a museum piece and then study it interactively at home later. After reviewing the model, the user might decide to upload his/her 3D data to a Cloud service in order to further refine the results there.

Determining the size of an object and reproducing faces     

The accuracy and sheer convenience of the modelling process is achieved by using the phone’s inertial sensors. The system automatically determines the correct moments to extract camera images based on the motion of the object to be captured. Contrary to image-only 3D capture solutions the app is also able to determine the absolute size and vertical direction of the object. Because of the complexity of the calculations needed to reconstruct hundreds of thousands of points, the phone’s graphics co-processor (GPU) is used to enable faster reconstruction and increase interactivity for the user. Moreover, the technology also allows the 3D capture of faces, i.e. adding a third dimension to portraits. So basically the ETH app can be used either to study a model through augmented reality applications or to use the scans to actually print out the 3D models.

By Pierre-Marie Mateo