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Learning to use illumination gradients as an unambiguous cue to three dimensional shape

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Harding2012PlosOne7e35950IlluminationGradients.pdf (386.8Kb)
Date
30/04/2012
Author
Harding, Glen
Harris, Julie
Bloj, Marina
Funder
EPSRC
Grant ID
EP/G038708/1
Keywords
RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
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Abstract
The luminance and colour gradients across an image are the result of complex interactions between object shape, material and illumination. Using such variations to infer object shape or surface colour is therefore a difficult problem for the visual system. We know that changes to the shape of an object can affect its perceived colour, and that shading gradients confer a sense of shape. Here we investigate if the visual system is able to effectively utilise these gradients as a cue to shape perception, even when additional cues are not available. We tested shape perception of a folded card object that contained illumination gradients in the form of shading and more subtle effects such as inter-reflections. Our results suggest that observers are able to use the gradients to make consistent shape judgements. In order to do this, observers must be given the opportunity to learn suitable assumptions about the lighting and scene. Using a variety of different training conditions, we demonstrate that learning can occur quickly and requires only coarse information. We also establish that learning does not deliver a trivial mapping between gradient and shape; rather learning leads to the acquisition of assumptions about lighting and scene parameters that subsequently allow for gradients to be used as a shape cue. The perceived shape is shown to be consistent for convex and concave versions of the object that exhibit very different shading, and also similar to that delivered by outline, a largely unrelated cue to shape. Overall our results indicate that, although gradients are less reliable than some other cues, the relationship between gradients and shape can be quickly assessed and the gradients therefore used effectively as a visual shape cue.
Citation
Harding , G , Harris , J & Bloj , M 2012 , ' Learning to use illumination gradients as an unambiguous cue to three dimensional shape ' , PLoS One , vol. 7 , no. 4 , e35950 . https://doi.org/10.1371/journal.pone.0035950
Publication
PLoS One
Status
Peer reviewed
DOI
https://doi.org/10.1371/journal.pone.0035950
ISSN
1932-6203
Type
Journal article
Rights
© 2012 Harding et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Collections
  • Institute of Behavioural and Neural Sciences Research
  • Psychology & Neuroscience Research
  • University of St Andrews Research
URI
http://hdl.handle.net/10023/3077

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