Traditional user interfaces for off-the-desktop applications are designed to display the output on flat 2D surfaces while the input is with 2D or 3D devices. In this paper, we focus on projectorbased augmented reality applications. We describe a framework to easily incorporate the interaction on a continuum of display surfaces and input devices. We first create a 3D understanding of the relationship between the user, the projectors and the display surfaces. Then we use some new calibration and rendering techniques to create a simple procedure to effectively illuminate the surfaces. We describe various underlying techniques and discuss the results in the context of three different applications.