Patch-based reconstruction and rendering of human heads

Reconstructing the 3D shape of human faces is an intensively researched topic. Most approaches aim at generating a closed surface representation of geometry, i.e. a mesh, which is texture-mapped for rendering. However, if free viewpoint rendering is the primary purpose of the reconstruction, representations other than meshes are possible. In this paper a coarse patch-based approach to both reconstruction and rendering is explored and applied not only to the face but the whole human head. The approach has advantages on parts of the scene that are traditionally difficult to reconstruct and render, which is the case for hair when it comes to human heads. In the paper, reconstruction of a patch is posed as a parameter estimation problem which is solved in a generic image-based optimization framework using the Levenberg-Marquard algorithm. In order to improve robustness, the Huber error metric is used and a geometric regularization strategy is introduced. Initial values for the optimization, which are crucial for the method´s success, are obtained by triangulation of SIFT feature points and a recursive expansion scheme.