Dioptra is a 3D model viewer for iPhone and iPad that also lets users measure distances on imported models. Open files such as GLB, glTF, USD, STL, PLY, or VRM, inspect the model from different angles, and tap two points to measure a distance. Measurements stay listed with the model, and users can set file units or switch between metric and imperial. The app also shows model dimensions and mesh details, opens supported interactive HTML exports, and organizes files into folders. The developer says models stay on-device and the app works offline without an account, cloud sync, or ads.
