Stereopsis in natural environments

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One of the most fundamental roles of the human visual system is to provide information about the depth and distance of objects in our environment so that we can interact with our world safely and effectively. Depth judgments are essential for tasks ranging from simple day-to-day objectives like reaching for your coffee, to the exquisite precision needed to perform microsurgery. Within personal interaction space, the binocular depth cue stereopsis is our most precise and accurate source of relative depth information. However, there is considerable debate concerning the accuracy of 3D depth percepts from stereopsis alone, and in combination with other depth cues. I propose that a primary cause of this controversy is the presence of conflicting depth cues in most experiments caused by the use of 3D displays and simplified rendered stimuli. The aim of this series of experiments is to resolve this debate by quantifying the interaction between stereopsis and monocular cues in the perception of depth using real physical objects. To do so, I will use a one-of-a-kind computer-controlled apparatus to present physical objects at precise locations with controlled lighting and motion. Stimuli will be designed using advanced modelling software and 3D printed to exact specifications; we will systematically manipulate the presence and consistency of depth cues such as binocular disparity, texture gradients, focal blur and motion parallax.  All experiments will use psychophysical methods (e.g. the method of constant stimuli) and probabilistic models will be used to compare the combination of depth cues with theoretical predictions. This research program will have significant impact in: 1) bridging the gap between studies using computer generated stimuli, and how we use depth information in the natural world 2) addressing the long-standing debate concerning the metric nature of individual depth cues and 3) clarifying the role of stereopsis in depth perception under natural conditions. The experiments proposed here are the core of a larger research program that ultimately will define the impact and importance of stereoscopic depth perception in our ability to effectively interact with the world. The results provide an important benchmark for studies of visual cue combination in natural environments. The implications of the work are far-reaching, for stereopsis is the cornerstone of 3D visualization in a wide range of fields from entertainment to microsurgery and flight simulation.