BRDF and geometry capture from extended inhomogeneous samples using flash photography

Abstract

We present a technique which allows capture of 3D surface geometry and a useful class of BRDFs using extremely simple equipment. A standard digital camera with an attached flash serves as a portable capture device, which may be used to sample geometry to very high resolution, as well as supplying samples over a large portion of the 4D space on which the BRDF is defined. Importantly, it allows capture of extended samples which may have spatially varying (inhomogeneous) BRDF. We demonstrate the system by capturing the geometry of complex materials with varying albedo and BRDF. We show in-situ capture of materials such as a brick wall and a human hand. The limitations of the system are that samples should be roughly planar, and that the BRDF should have some diffuse component in order that a first approximation to the normals can be computed. However, given the simplicity and ease of use of the system (it takes a few minutes to carefully capture a hand), and the ability to capture extended surfaces without any range capture device such as a laser scanner we argue that it is a valuable addition to the range of real-world BRDF capture systems in the literature. We extend standard photometric stereo techniques by moving both the camera and the light source. By incorporating automatic parallax correction we allow the capture of surfaces which are quite far from planar.