1. Method of displaying a 3D image in actual space including the steps of: (1) providing a display panel that revolves about a reference axis while keeping its surface always facing a fixed direction, said display panel comprising a matrix of pixels that can be addressed from a set of column electrode lines and a set of row electrode lines, said display panel sweeping a display space; (2) defining an orthogonal 3D grid structure just covering said display space; (3) processing said 3D image into an orthogonal stack of image slices based on said orthogonal 3D grid structure, each said image slice having its surface normal direction facing said fixed direction; (4) converting said image slices into image frames to be displayed on said display panel based on following relation: 
 pmy=py−R/dN− ( R/dN ) sin θ, 
 θ=cos −1 (1− pz dT/R ), wherein pmy is grid element location index in v direction on said image slices, py is pixel location index in y direction on said image frames, said y direction is perpendicular to said reference axis and to said fixed direction, both location indices have origins on the same side of the slice or frame, R is rotation radius of said display panel, dT is distance between adjacent image frames, dN is pixel pitch of said display panel, pz is frame index number starting at 0 from top position, θ is angle of rotation of said display panel measured from top position of said display panel; (5) displaying said image frames on said display panel in sequence.