Figure - available from: Royal Society Open Science
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In the between-object condition, the manipulation of luminance was based on the distances of all points in an object considered together, to create (a) reduced and (b) enhanced conditions. (c) shows a luminance sample in the reduced and enhanced condition for a far object (the lemon) and (d) shows samples for a close object (the onion). In the reduced condition, the far object is made brighter and the close object darker in comparison with the enhanced condition. (e)There was a positive correlation between the mean luminance and distance of objects. This positive correlation increased in our reduced condition, and was negative in our enhanced condition.
Source publication
The perception of depth from retinal images depends on information from multiple visual cues. One potential depth cue is the statistical relationship between luminance and distance; darker points in a local region of an image tend to be farther away than brighter points. We establish that this statistical relationship acts as a quantitative cue to...
Citations
... However this exclusion criterion was not used, because in the hypothesised event that the shadow was visible and being aligned with the reference at either end on the table, but the target was subsequently located beyond, this would have led to the removal of trials in which the participant was following a coherent strategy. Lighting conditions experienced in daily life tend to include ambient light from overcast weather diffusing the light source, and directional lighting, for example from the sun or from ceiling lights 32 . The lighting conditions used here were created to replicate these, with overtly visible cast shadow effects (with the notable exception of the Ambient lighting condition). ...
Shadows in physical space are copious, yet the impact of specific shadow placement and their abundance is yet to be determined in virtual environments. This experiment aimed to identify whether a target’s shadow was used as a distance indicator in the presence of binocular distance cues. Six lighting conditions were created and presented in virtual reality for participants to perform a perceptual matching task. The task was repeated in a cluttered and sparse environment, where the number of cast shadows (and their placement) varied. Performance in this task was measured by the directional bias of distance estimates and variability of responses. No significant difference was found between the sparse and cluttered environments, however due to the large amount of variance, one explanation is that some participants utilised the clutter objects as anchors to aid them, while others found them distracting. Under-setting of distances was found in all conditions and environments, as predicted. Having an ambient light source produced the most variable and inaccurate estimates of distance, whereas lighting positioned above the target reduced the mis-estimation of distances perceived.
