Estimating the Illumination Direction From Three-Dimensional Texture of Brownian Surfaces

Sylvia Pont, A.J. van Doorn, Jan Koenderink

Research output: Contribution to journalArticleScientificpeer-review

2 Citations (Scopus)
54 Downloads (Pure)

Abstract

We studied whether human observers can estimate the illumination direction from 3D textures of random Brownian surfaces, containing undulations over a range of scales. The locally Lambertian surfaces were illuminated with a collimated beam from random directions. The surfaces had a uniform albedo and thus texture appeared only through shading and shadowing. The data confirm earlier results with Gaussian surfaces, containing undulations of a single scale. Observers were able to accurately estimate the source azimuth. If shading dominated the images, the observers committed 180° errors. If cast shadows were present, they resolved this convex-concave-ambiguity almost completely. Thus, observers relied on second-order statistics in the shading regime and used an unidentified first-order cue in the shadow regime. The source elevations could also be estimated, which can be explained by the observers’ exploitation of the statistical homogeneity of the stimulus set. The fraction of the surface that is in shadow and the median intensity are likely cues for these elevation estimates.
Original languageEnglish
Pages (from-to)1-18
Journali-Perception
Volume8
Issue number2
DOIs
Publication statusPublished - 2017

Keywords

  • Brownian surface
  • illumination direction
  • illuminance flow
  • light field
  • shading
  • shadowing
  • texture
  • OA-Fund TU Delft

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