1. Introduction
Face alignment is critical to face analysis applications, such as face identification [2], [29], face tracking [25], and face synthesis [8], [6], [13]. Compared with 2D face alignment methods [24], [18], [14], [23], 3D face alignment is more robust to variation of occlusions and out-of-plane rotations, and has stronger representational power for describing face shapes [20], [27], [5], [19]. 3D face alignment and reconstruction have made rapid advances in recent years, especially after the utilization of deep convolution neural networks (CNN) for solving the problem [5], [1], [27], [7], [21]. Previous approaches can be divided into two categories according to input data type, the methods based on single-view and the methods based on multi-view. Due to space constrains, we mainly focus on the recently proposed methods related with our work from the above two categories, then discuss their advantages and drawbacks, respectively.