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

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

Pont, S.C. (TU Delft Human Information Communication Design)
van Doorn, A.J. (Katholieke Universiteit Leuven; Universiteit Utrecht)
Koenderink, J.J. (Katholieke Universiteit Leuven; Universiteit Utrecht)

2017

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.

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

http://resolver.tudelft.nl/uuid:68548e94-6f68-4081-afa8-564adc3f1eb4

https://doi.org/10.1177/2041669517701947

2041-6695

i-Perception, 8 (2), 1-18

Institutional Repository

journal article

© 2017 S.C. Pont, A.J. van Doorn, J.J. Koenderink