Embedding Shepard’s Interpolation into CNN Models for Unguided Depth Completion

When acquiring sparse data samples, an interpolation method is often needed to fill in the missing information. An example application, known as “depth completion”, consists in estimating dense depth maps from sparse observations (e.g. LiDAR acquisitions). To do this, algorithmic methods fill the depth image by performing a sequence of basic image processing operations, while recent approaches propose data-driven solutions, mostly based on Convolutional Neural Networks (CNNs), to predict the missing information. In this work, we combine learning-based and classical algorithmic approaches to ideally exploit the performance of the former with the ability to generalize of the latter. First, we define a novel architecture block called IDWBlock. This component allows to embed Shepard’s interpolation (or Inverse Distance Weighting, IDW) into a CNN model, with the advantage of requiring a small number of parameters regardless of the kernel size. Second, we propose two network architectures involving a combination of the IDWBlock and learning-based depth completion techniques. In the experimental section, we tested the models’ performances on the KITTI depth completion benchmark and NYU-depth-v2 dataset, showing how they present strong robustness to input sparsity under different densities and patterns.