  The task of predicting 3D eye gaze from eye images can be performed either by
(a) end-to-end learning for image-to-gaze mapping or by (b) fitting a 3D eye
model onto images. The former case requires 3D gaze labels, while the latter
requires eye semantics or landmarks to facilitate the model fitting. Although
obtaining eye semantics and landmarks is relatively easy, fitting an accurate
3D eye model on them remains to be very challenging due to its ill-posed nature
in general. On the other hand, obtaining large-scale 3D gaze data is cumbersome
due to the required hardware setups and computational demands. In this work, we
propose to predict 3D eye gaze from weak supervision of eye semantic
segmentation masks and direct supervision of a few 3D gaze vectors. The
proposed method combines the best of both worlds by leveraging large amounts of
weak annotations--which are easy to obtain, and only a few 3D gaze
vectors--which alleviate the difficulty of fitting 3D eye models on the
semantic segmentation of eye images. Thus, the eye gaze vectors, used in the
model fitting, are directly supervised using the few-shot gaze labels.
Additionally, we propose a transformer-based network architecture, that serves
as a solid baseline for our improvements. Our experiments in diverse settings
illustrate the significant benefits of the proposed method, achieving about 5
degrees lower angular gaze error over the baseline, when only 0.05% 3D
annotations of the training images are used. The source code is available at
https://github.com/dimitris-christodoulou57/Model-aware_3D_Eye_Gaze.
