Light direction from shad(ow)ed random Gaussian surfaces

Journal Article (2004)
Author(s)

J.J. Koenderink (Universiteit Utrecht)

A.J. van Doorn (Universiteit Utrecht)

SC Pont (Universiteit Utrecht)

Affiliation
External organisation
DOI related publication
https://doi.org/10.1068/p5287
More Info
expand_more
Publication Year
2004
Language
English
Affiliation
External organisation
Issue number
12
Volume number
33
Pages (from-to)
1405-1420

Abstract

Three human observers estimated the illumination direction for samples of random Gaussian surfaces illuminated by a collimated beam from random directions. These stimuli appear as 'texture' due to shading and shadowing (the surface on the microscale was Lambertian of uniform albedo; thus texture appears only through shading and shadowing). We found that observers were able to estimate the azimuth of the source with remarkable accuracy. In the shading regime (no shadows) the observers committed 180° azimuth errors with 50% probability, whereas in the shadow-dominated regime they were able to avoid this convex/concave confusion to a large extent. They evidently relied on second-order statistics in the shading regime and used an unidentified first-order cue in the shadow regime. The elevations of the source were also estimated with remarkable precision. We attribute this to the statistical homogeneity of the sample which can apparently be exploited by the observers. Likely cues are the fraction of shadowed surface, average intensity and rms contrast. The ability of human observers to estimate the illumination direction from surface texture no doubt contributes to the ability to estimate the light field in scenes, which is a prerequisite to the photometric parsing of scenes (shape from shading, and so forth).

No files available

Metadata only record. There are no files for this record.