Volumetric displays are a branch of the 3D display family. A visual representation of an entity is created by the emission, scattering, or relaying of illumination throughout a 3D space (Holographic displays only scatter light at a 2D surface), with the emitters being co-located with the real image points. Volumetric displays can be viewed without glasses or headsets. The user can view the display from any angle because the emitters are co-located with the real image points.