Radiometric Correction in the CoRE Display Environment

Front-projection display systems suffer from a fundamental problem: the user can easily and inadvertently block the projector, creating shadows. The framework we present in this paper enables a front-projected display system to solve this problem and remove display surface shadows in real-time. Shadows are an example of radiometric inconsistencies, which cause a number of challenges in building large display systems. Other radiometric anomalies arise from reflectance variations across the display surface, inconsistencies between projectors, and inter-reflections from the display surfaces themselves. We present a new automated technique for dynamically creating a radiometrically constant image on the display surface. Our technique detects and corrects for radiometric anomalies as transient as shadows, accommodates variations in the reflectance characteristics of the display surface, and can address the display-surface inter-reflection problem. Using an automatically-derived relative position of cameras and projectors in the display environment, we render an expected image for each camera location. When a camera observes the displayed image, we compare the expected image to the observed one in order to derive an alpha mask that is back-projected into each display buffer to correct for intensity variation on the display. We demonstrate an implementation of the technique to remove shadows in a multi-projector front projection system.