The role of texture amplitude in shape from shading: evidence from a haptic matching task

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

Research output: Contribution to journalConference abstractpeer-review


The pattern of illumination on an undulating surface can be used to infer its 3-D form (shape from shading). But the recovery of shape would be invalid if the shading actually arose from reflectance variation. When a corrugated surface is painted with an albedo texture, the variation in local mean luminance (LM) due to shading is accompanied by a similar modulation in texture amplitude (AM). This is not so for reflectance variation, nor for roughly textured surfaces. We used a haptic matching technique to show that modulations of texture amplitude play a role in the interpretation of shape from shading. Observers were shown plaid stimuli comprising LM and AM combined in-phase (LM+AM) on one oblique and in anti-phase (LM-AM) on the other. Stimuli were presented via a modified ReachIN workstation allowing the co-registration of visual and haptic stimuli. In the first experiment, observers were asked to adjust the phase of a haptic surface, which had the same orientation as the LM+AM combination, until its peak in depth aligned with the visually perceived peak. The resulting alignments were consistent with the use of a lighting-from-above prior. In the second experiment, observers were asked to adjust the amplitude of the haptic surface to match that of the visually perceived surface. Observers chose relatively large amplitude settings when the haptic surface was oriented and phase-aligned with the LM+AM cue. When the haptic surface was aligned with the LM-AM cue, amplitude settings were close to zero. Thus the LM/AM phase relation is a significant visual depth cue, and is used to discriminate between shading and reflectance variations. [Supported by the Engineering and Physical Sciences Research Council, EPSRC].
Original languageEnglish
Pages (from-to)416
Issue number3
Publication statusPublished - 1 Mar 2006
Event10th Applied Vision Association Christmas Meeting - Aston University, Birmingham (UK), United Kingdom
Duration: 19 Dec 2005 → …


  • illumination
  • undulating surface
  • 3-D form
  • reflectance variation
  • local mean luminance
  • texture amplitude
  • visual depth cue
  • shading
  • reflectance variations


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