  Face reconstruction and tracking is a building block of numerous applications
in AR/VR, human-machine interaction, as well as medical applications. Most of
these applications rely on a metrically correct prediction of the shape,
especially, when the reconstructed subject is put into a metrical context
(i.e., when there is a reference object of known size). A metrical
reconstruction is also needed for any application that measures distances and
dimensions of the subject (e.g., to virtually fit a glasses frame).
State-of-the-art methods for face reconstruction from a single image are
trained on large 2D image datasets in a self-supervised fashion. However, due
to the nature of a perspective projection they are not able to reconstruct the
actual face dimensions, and even predicting the average human face outperforms
some of these methods in a metrical sense. To learn the actual shape of a face,
we argue for a supervised training scheme. Since there exists no large-scale 3D
dataset for this task, we annotated and unified small- and medium-scale
databases. The resulting unified dataset is still a medium-scale dataset with
more than 2k identities and training purely on it would lead to overfitting. To
this end, we take advantage of a face recognition network pretrained on a
large-scale 2D image dataset, which provides distinct features for different
faces and is robust to expression, illumination, and camera changes. Using
these features, we train our face shape estimator in a supervised fashion,
inheriting the robustness and generalization of the face recognition network.
Our method, which we call MICA (MetrIC fAce), outperforms the state-of-the-art
reconstruction methods by a large margin, both on current non-metric benchmarks
as well as on our metric benchmarks (15% and 24% lower average error on NoW,
respectively).
