Luminance and Surface Texture Discontinuities Affect Perception of Object Reachability in Virtual Reality.

We investigated the effects of surface texture discontinuities and surface luminance on the perception of an object's reachability. Fifty-four naïve subjects were tested in an affordance paradigm where participants provided judgments about the reachability of a small graspable virtual object (a ping-pong ball) in several virtual scenes using the Oculus Rift virtual reality headset. Participants viewed objects at distances defined as intrinsic ratios of object distance to arm-length. Seven pi-ratios ranging from 0.7 to 1.3 were used during testing, such that anything less than or equal to 1.0 was considered reachable and anything greater than 1.0 was considered not reachable. In Experiment 1, stimuli were randomized across four tabletop conditions in which we varied both surface luminance and the presence of a surface texture discontinuity. Luminance varied as the ratio of white-to-black surface texture; high luminance tabletops were all white or mostly white, low luminance tabletops were all black or mostly black. When present, the discontinuity occurred 50cm from the participant where the edges of the two textures met. In Experiment 2, stimuli were randomized across five tabletop conditions in which both the presence and location of the discontinuity were varied, along with luminance. The discontinuity occurred at 25%, 50%, and 75% of the table's length away from the participant. We found significant interactions between discontinuity and pi and between luminance and pi. These effects indicate that subjects were more likely to respond "no" to the reachability question both when a discontinuity was present as pi-ratios increased, and under high luminance conditions as pi-ratios increased. Light (i.e., the information for vision) and surface texture gradients carry consequences for the realization of reaching affordances both in the real world and in virtual environments. Meeting abstract presented at VSS 2018