  We present Neural Contact Fields, a method that brings together neural fields
and tactile sensing to address the problem of tracking extrinsic contact
between object and environment. Knowing where the external contact occurs is a
first step towards methods that can actively control it in facilitating
downstream manipulation tasks. Prior work for localizing environmental contacts
typically assume a contact type (e.g. point or line), does not capture
contact/no-contact transitions, and only works with basic geometric-shaped
objects. Neural Contact Fields are the first method that can track arbitrary
multi-modal extrinsic contacts without making any assumptions about the contact
type. Our key insight is to estimate the probability of contact for any 3D
point in the latent space of object shapes, given vision-based tactile inputs
that sense the local motion resulting from the external contact. In
experiments, we find that Neural Contact Fields are able to localize multiple
contact patches without making any assumptions about the geometry of the
contact, and capture contact/no-contact transitions for known categories of
objects with unseen shapes in unseen environment configurations. In addition to
Neural Contact Fields, we also release our YCB-Extrinsic-Contact dataset of
simulated extrinsic contact interactions to enable further research in this
area. Project page: https://github.com/carolinahiguera/NCF
