This is the first I've heard of it, and the trailer is beyond description. Loving Vincent is the story of the life and death of painter Vincent van Gogh, and every frame of the film has been painted by a crew of over 100 artists. Do check it out. They discuss the technique on the official website. Here are just a few screenshots from the trailer:
I really hope this film fulfills its promise. It releases in the U.S. on September 22.
H/T to ArcLight Cinemas on Facebook for the trailer.