Closer Object Looks Smaller: Investigating the Duality of Size Perception in a Spherical Fish Tank VR Display.

Fish Tank Virtual Reality (FTVR) displays provide compelling 3D experiences by rendering view-dependent imagery on a 2D screen. While users perceive a 3D object in space, they are actually looking at pixels on a 2D screen, thus, a perceptual duality exists between the object's pixels and the 3D percept potentially interfering with the experience. To investigate, we conducted an experiment to see whether the on-screen size of the 2D imagery affects the perceived object size in 3D space with different viewing conditions, including stereopsis. We found that the size of on-screen imagery significantly influenced object size perception, causing 83.3% under/overestimation of perceived size when viewing without stereopsis and reducing to 64.7% with stereopsis. Contrary to reality, objects look smaller when the viewer gets closer. Understanding the perceptual duality helps us to provide accurate perception of real-world objects depicted in the virtual environment and pave the way for 3D applications.