The aim in this paper is to use principal geodesic analysis to model the statistical variations for sets of facial needle
maps. We commence by showing how to represent the distribution of surface normals using the exponential map. Shape deformations
are described using principal geodesic analysis on the exponential map. Using ideas from robust statistics we show how this
deformable model may be fitted to facial images in which there is significant self-shadowing. Moreover, we demonstrate that
the resulting shape-from-shading algorithm can be used to recover accurate facial shape and albedo from real world images.
In particular, the algorithm can effectively fill-in the facial surface when more than 30% of its area is subject to self-shadowing.
To investigate the utility of the shape parameters delivered by the method, we conduct experiments with illumination insensitive
face recognition. We present a novel recognition strategy in which similarity is measured in the space of the principal geodesic
parameters. We also use the recovered shape information to generate illumination normalized prototype images on which recognition
can be performed. Finally we show that, from a single input image, we are able to generate the basis images employed by a
number of well known illumination-insensitive recognition algorithms. We also demonstrate that the principal geodesics provide
an efficient parameterization of the space of harmonic basis images.
Keywords Shape-from-shading - Face recognition - Principal geodesic analysis