The app scans your face into a 3D image and allows you to see how glasses would really look on your face.
The iPad captures the images and then sends them over a Wi-Fi, 3G, or 4G connection to a data center. There, the images are processed and a 3D rendering is sent back to the iPad. That process takes maybe 30 seconds or so. Once you scan your face, it’s easy to try on new glasses.