  We present a novel approach for recovering 3D shape and view dependent
appearance from a few colored images, enabling efficient 3D reconstruction and
novel view synthesis. Our method learns an implicit neural representation in
the form of a Signed Distance Function (SDF) and a radiance field. The model is
trained progressively through ray marching enabled volumetric rendering, and
regularized with learning-free multi-view stereo (MVS) cues. Key to our
contribution is a novel implicit neural shape function learning strategy that
encourages our SDF field to be as linear as possible near the level-set, hence
robustifying the training against noise emanating from the supervision and
regularization signals. Without using any pretrained priors, our method, called
SparseCraft, achieves state-of-the-art performances both in novel-view
synthesis and reconstruction from sparse views in standard benchmarks, while
requiring less than 10 minutes for training.
