The role of local luminance amplitude in the interpretation of shape-from-shading in textured surfaces

Andrew J. Schofield, Mark A. Georgeson, Gillian Hesse, P.B. Rock, Timothy A. Yates

Research output: Contribution to conferencePaper

Abstract

Luminance changes within a scene are ambiguous; they can indicate reflectance changes, shadows, or shading due to surface undulations. How does vision distinguish between these possibilities? When a surface painted with an albedo texture is shaded, the change in local mean luminance (LM) is accompanied by a similar modulation of the local luminance amplitude (AM) of the texture. This relationship does not necessarily hold for reflectance changes or for shading of a relief texture. Here we concentrate on the role of AM in shape-from-shading. Observers were presented with a noise texture onto which sinusoidal LM and AM signals were superimposed, and were asked to indicate which of two marked locations was closer to them. Shape-from-shading was enhanced when LM and AM co-varied (in-phase), and was disrupted when they were out-of-phase. The perceptual differences between cue types (in-phase vs out-of-phase) were enhanced when the two cues were present at different orientations within a single image. Similar results were found with a haptic matching task. We conclude that vision can use AM to disambiguate luminance changes. LM and AM have a positive relationship for rendered, undulating, albedo textures, and we assess the degree to which this relationship holds in natural images. [Supported by EPSRC grants to AJS and MAG].
Original languageEnglish
Publication statusUnpublished - 2006
Event29th European Conference on Visual Perception - St Petersburg , Russian Federation
Duration: 20 Aug 200625 Aug 2006

Conference

Conference29th European Conference on Visual Perception
CountryRussian Federation
CitySt Petersburg
Period20/08/0625/08/06

Bibliographical note

Abstract published in ECVP 2006 Abstract Supplement, Perception, 35(Suppl. S), p. 227. ISSN 0001-4966

Keywords

  • luminance changes
  • indicate reflectance changes
  • shadows
  • surface undulations
  • local mean luminance
  • local luminance amplitude
  • texture
  • disambiguate luminance changes

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    Schofield, A. J., Georgeson, M. A., Hesse, G., Rock, P. B., & Yates, T. A. (2006). The role of local luminance amplitude in the interpretation of shape-from-shading in textured surfaces. Paper presented at 29th European Conference on Visual Perception, St Petersburg , Russian Federation.