This paper presents a novel volumetric display based on projection on a non-planer and reconfigurable fog screen. Unlike conventional fog projection systems which produce 2D images on flat screens, our display scatters different parts of the projected image at different depth levels, thus allowing volumetric data to be displayed in the real 3D space. We constructed the fog screen with a 2D array of nozzles that are individually switchable, while the switching pattern is tightly synchronized with the video content. Our system is superior to many existing approaches at many levels. First, our display does not require head tracking, glasses or head-mounted devices while allowing high resolution, full color 3D image to be observed from wide viewing angles by many people at the same time. As compare with various existing approaches, our system is relatively easy to setup and low cost. Most importantly, our immaterial, mid-air display allows users to directly touch and manipulate virtual objects in 3D under marker-free and barrier-free settings which opens up immense tangible and creative interaction possibilities. In this paper, we provide the details of display mechanism and design prototype, as well as a constrained optimization problem to find the projection distance that can maximize the display resolution. A number of real display examples will demonstrate the performance of the proposed system.