Relighting with the Reflected Irradiance Field: Representation, Sampling and Reconstruction

Abstract

Image-based relighting (IBL) is a technique to change the illumination of an image-based object/scene. In this paper, we define a representation called the reflected irradiance field which records the reflection from an object surface ir-radiated by a point light source that moves on a plane. This representation is dual to that of the light field. It synthe-sizes a novel image under a different illumination by in-terpolating and superimposing appropriate recorded sam-ples. Furthermore, we study the minimum sampling prob-lem of the reflected irradiance field, i.e., how many point light sources are needed during sampling. We find that there exists a geometry-independent bound for the sampling in-terval whenever the second-order derivatives of the surface BRDF and the minimum depth of the scene are bounded. This bound ensures that the error in the reconstructed im-age is controlled by a given tolerance, regardless of the ge-ometry. Experiments on both synthetic and real surfaces are conducted to verify our analysis. 1