  In this paper, we provide a detailed survey of 3D Morphable Face Models over
the 20 years since they were first proposed. The challenges in building and
applying these models, namely capture, modeling, image formation, and image
analysis, are still active research topics, and we review the state-of-the-art
in each of these areas. We also look ahead, identifying unsolved challenges,
proposing directions for future research and highlighting the broad range of
current and future applications.
