Not all shapes are flat on one side and have no hollows. Most shapes do not match that criterion. So, on most 3D printers, they have to add sacrificial support

Not all shapes are flat on one side and have no hollows. Most shapes do not match that criterion. So, on most 3D printers, they have to add sacrificial support structures. Also, most 3D printers add material a layer at a time, which is very slow. This one starts out with all the resin at its final position, so only the light moves.