This paper presents a new fast and accurate self-shadowing algorithm for animated hair. Our method is based on a 3D light-oriented density map, a novel structure that combines an optimized volumetric representation of hair with a light-oriented partition of space. Using this 3D map, accurate hair self-shadowing can be interactively processed (several frames per second for a full hairstyle) on a standard CPU. Beyond the fact that our application is independent of any graphics hardware (and thus portable), it can easily be parallelized for better performance. Our method is especially adapted to render animated hair since there is no geometry-based precomputation and since the density map can be used to optimize hair self-collisions. The approach has been validated on a dance motion sequence, for various hairstyles.