Projection-based augmented reality (AR) is a promising medium for realizing pervasive computing environment, and yet the problem of determining projection-suitable regions and where to project remains. To tackle this problem, we introduce FRISP, a projectionbased augmented reality (AR) Framework designed for Registering Interactive Spatial Projection. The FRISP framework utilizes a pantilt projection-camera (pro-cam) system for capturing geometry and projection mapping. The framework scans and analyzes the geometric properties of a room, in order to determine projection-suitable regions and generate multi-window layouts. Once the multi-windows are registered to the real world, they can be interacted with by the users. The users can assign various widgets or applications to the multi-windows, which are then finally augmented onto the real world and can serve as a base units for realizing the pervasive AR environment.