On Partial Shape Correspondence and Functional Maps

While dealing with matching shapes to their parts, we often utilize an instrument known as functional maps. The idea is to translate the shape matching problem into ``convenient'' spaces by which matching is performed algebraically by solving a least squares problem. Here, we argue that such formulations, though popular in this field, introduce errors in the estimated match when partiality is invoked. Such errors are unavoidable even when considering advanced feature extraction networks, and they can be shown to escalate with increasing degrees of shape partiality, adversely affecting the learning capability of such systems. To circumvent these limitations, we propose a novel approach for partial shape matching. Our study of functional maps led us to a novel method that establishes direct correspondence between partial and full shapes through feature matching bypassing the need for functional map intermediate spaces. The Gromov distance between metric spaces leads to the construction of the first part of our loss functions. For regularization we use two options: a term based on the area preserving property of the mapping, and a relaxed version of it without the need to compute a functional map. The proposed approach shows superior performance on the SHREC'16 dataset, outperforming existing unsupervised methods for partial shape matching. In particular, it achieves state-of-the-art result on the SHREC'16 HOLES benchmark, superior also compared to supervised methods.