Portrait mode photos like a 3D scene and add up to 30 virtual lights in them - No IAP - Featured as App of The Day.
Link - to get a taste of the app functionality.
The app reads the depth data of a Portrait mode photo and creates a 3D representation of it. Then, it generates data like per pixel surface orientation (normal map). After all data is calculated and gone through a pipeline of filters to improve quality the user can add light sources to the photo and edit their parameters e.g.: position, colour, intensity, specularity (reflectivity). All light sources cast shadows on the original photo and the user can turn them on/off and adjust their sharpness. There are additional depth related effects that the user can apply on the photo like: fog and background removal. All actions of the user are done in realtime, there is zero loading/delay in user input. It's like a game where the user moves lights over their photos.