PHD-Project2-RealismStudy_Experiment_Codes.

#Introduction: Virtual Reality aims to convey 3d scene structure as compellingly as possible. Although stereoscopic imagery results in a vivid sense of depth, perceived realism of 3d space has been shown to reduce as the depth separation between stimulus elements increases (Hibbard et al., 2017). A possible reason is that conventional stereoscopic displays present images on a single focal plane, resulting in increasingly incorrect focus cues (stimulus to accommodation; retinal blur gradient) as depth separation increases. Using a multiple-focal-planes stereoscopic display (MacKenzie et al., 2010) we compared perceived realism of 3d space in conventional stereoscopic images, and equivalent images presented with correct focus cues. The stimuli were random-dot stereograms depicting two planes separated in depth. The depth separation between planes varied across trials. Participants (N=15) judged which of two stimuli, presented consecutively, contained the more realistic 3d separation (2-IFC task). Participants were instructed to look between near and far planes during the task. All possible pairwise combinations of depth separation and focus-cue condition were presented. Thurstonian scaling was used to derive relative realism scores in each case. Perceived realism was consistently higher with correct focus cues than with conventional 3d stereoscopic presentation. Moreover, when focus cues were correct, perceived realism did not decrease with increased depth separation, but instead remained constant. Our results indicate that correct focus cues improve the perceived realism of 3d space in stereoscopic images, and so could potentially contribute to Virtual Reality that is more compelling