  Scene flow is the dense 3D reconstruction of motion and geometry of a scene.
Most state-of-the-art methods use a pair of stereo images as input for full
scene reconstruction. These methods depend a lot on the quality of the RGB
images and perform poorly in regions with reflective objects, shadows,
ill-conditioned light environment and so on. LiDAR measurements are much less
sensitive to the aforementioned conditions but LiDAR features are in general
unsuitable for matching tasks due to their sparse nature. Hence, using both
LiDAR and RGB can potentially overcome the individual disadvantages of each
sensor by mutual improvement and yield robust features which can improve the
matching process. In this paper, we present DeepLiDARFlow, a novel deep
learning architecture which fuses high level RGB and LiDAR features at multiple
scales in a monocular setup to predict dense scene flow. Its performance is
much better in the critical regions where image-only and LiDAR-only methods are
inaccurate. We verify our DeepLiDARFlow using the established data sets KITTI
and FlyingThings3D and we show strong robustness compared to several
state-of-the-art methods which used other input modalities. The code of our
paper is available at https://github.com/dfki-av/DeepLiDARFlow.
