Document Detail

Estimating local shape from shading in the presence of global shading.
MedLine Citation:
PMID:  8414892     Owner:  NLM     Status:  MEDLINE    
In theory, global shading may help with the estimation of local surface structure from shading (e.g., in specifying the illuminant direction). Empirically, we do not know whether human observers combine the information given by the local and global shading to estimate local shape. Observers had to indicate the orientation of a local elongated perturbation with or without global shading information provided by a background surface. Our psychophysical results show the following: 1. Observers do not estimate the orientation of the local perturbation more accurately with global shading information than they do in the absence of such information. 2. Responses depend dramatically on the inclination between the illuminant direction and the viewing direction. For an inclination of 20 degrees, observers indicate more or less the orientation of the local ridge; however, for an inclination of 40 degrees, they indicate either the direction of the illuminant or an orientation close to the shadow edge of the perturbation. Most subjects show some combination of these behaviors. This behavior is not altered by global shading information. We conclude that in our paradigm, global shading information does not aid the estimation of local shape.
R G Erens; A M Kappers; J J Koenderink
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Perception & psychophysics     Volume:  54     ISSN:  0031-5117     ISO Abbreviation:  Percept Psychophys     Publication Date:  1993 Sep 
Date Detail:
Created Date:  1993-11-17     Completed Date:  1993-11-17     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0200445     Medline TA:  Percept Psychophys     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  334-42     Citation Subset:  C    
University of Utrecht, The Netherlands.
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MeSH Terms
Form Perception*
Visual Perception*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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