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.

Microgeometry capture using an elastomeric sensor

“…Effort has also been placed in hybrid approaches that simultaneously infer shape and reflectance from photographs [Wang and Dana 2004;Goldman et al 2005;Paterson et al 2005;Ruiters and Klein 2009]. With sufficient input these methods can produce good results, but must make some assumptions (such as moderately diffuse BRDFs [Paterson et al 2005]) because the simultaneous reflectance and geometry problem is fundamentally underconstrained.…”

Non-rigid Photometric Stereo with Colored Lights

“…We prefer to estimate the mapping by employing an easy-to-use calibration tool (Figure 1 (right)) similar to the one used in [16]. The pattern is planar with special markings that allow the plane orientation to be estimated.…”

Transfer of albedo and local depth variation to photo-textures

“…Researchers have built upon the idea of the use of multiple light sources (photometric stereo) [36] to capture material appearance from fewer view points, effectively recovering albedo and local surface orientation [28,12]. Paterson et al's [26] material capture approach combines photometric stereo with multiple view geometry captures to recover displacement maps and inhomogeneous BRDFs over nearly planar samples. Ward and Glencross [32] employ a similar approach to estimate albedo (diffuse reflectance), based on single view multi-flash captures in conjunction with shape from shading [16,21,39,13].…”