Understanding the geometrical properties of an Ames room and controlling it systematically and quantitatively

Abstract

Within an Ames room, the perceived size of objects, such as people, changes dynamically when the objects move about within the room. The shape of the Ames room is not actually rectangular but it is perceived to be rectangular. Unfortunately, the geometrical properties of the Ames room have often been misunderstood, and rooms that have different shapes are also referred to as “Ames rooms” in many articles. In this study, the geometrical properties of the original Ames rooms constructed by Adelbert Ames, Jr. were analyzed. We found that these original Ames rooms are 3D-to-3D perspective transformations of rectangular illusory rooms. Based on this analysis, we also developed a computational model that can construct a generalized Ames room that has a hexahedral shape with some free parameters that quantitatively control (i) the size and aspect-ratio of a rectangular illusory room, (ii) the amount of distortion of the Ames room from a rectangular room, and (iii) the viewpoint of an observer. This model was implemented as a computational program so that an Ames room can be constructed in a VR space. It also allows us to design an Ames room that depends on the size of the available real space and to physically construct the Ames room in this real space.