I think the title and the image says it all. However I'll have spill some details out for myself because I might forget what I was thinking. The thing is, having multiple viewers, is just a matter of solving a system of equations. Such that every viewer's eye will see certain pixels. With eye tracking we can control the blinds accordingly, up to a fixed number of viewers. The engineering factor of how to implement those blinds may be regarded as layering several blinds, those same ones used for one viewer 3D glassless stereoscopy.