Projection-based user interface

Techniques for providing a virtual touch screen are described. An example of a computing device with a virtual touch screen includes a projector to project a user interface image onto a touch surface, and a depth camera to generate a depth image representing objects in a vicinity of the user interface image, and a touch mask generator. The computing device also includes a touch detection module to analyze the touch mask to detect touch events. The touch detection module is configured to identify a finger in the touch mask, identify a centroid region of the finger and compute a distance of the centroid region from a touch surface, and compare the distance to a threshold distance to identify a touch event.