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Specular Reflections and the Perception of Shape

Specular Reflections and the Perception of Shape Roland W. Fleming, Antonio Torralba, Edward H. Adelson Journal of Vision (2004). observation : we are able to recover some depth using only specular reflections problem: how is this accomplished? no “traditional” cues available

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Specular Reflections and the Perception of Shape

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  1. Specular Reflections and the Perception of Shape Roland W. Fleming, Antonio Torralba, Edward H. Adelson Journal of Vision (2004)

  2. observation: we are able to recover some depth using only specular reflections problem: how is this accomplished? no “traditional” cues available - motion - disparity - texture - lambertian shading

  3. can we really recover depth from specularities? Savarese, Li, Perona (2004): No, they’re “only a very weak cue.” • 3 objects • - patch w/spec reflections • - subjects try to guess original object in 3 expts:

  4. can we really recover depth from specularities? Fleming, et al (2003, 2004): Yes, and “reliably and quite acccurately.” • stimuli: irregular, smooth, w/boundaries • subjects adjust randomly initialized normals to perceived orientation

  5. what information is available?

  6. what information is available? ...and we don’t rely on boundaries

  7. what information is available? a relationship between curvature and reflection compression

  8. we have to make some assumptions • about the object • about the surroundings • texture compression can be computed quickly (though roughly) with filters • using steerable pyramid • 24 filter orientations at each location • 1 scale – very local

  9. texture compression can be computed quickly (though roughly) with filters • using steerable pyramid • 24 filter orientations at each location • 1 scale – very local

  10. stable across different scenes

  11. stable across different scenes

  12. correspondence between truth and guesswork

  13. how realistic are the stimuli? • smoothness • - limited world scenes • specularity only

  14. orientation fields for shaded/specular objects can be consistent

  15. ...or very inconsistent

  16. so how do we disambiguate the two?

  17. discussion • claims • simple, quick computations can give some information about depth • evaluation • subjects can perceive shape from specularity alone • orientation field and its anisotropy correlate with curvature • this is stable across scenes and varies shape-to-shape • reflection-induced orientation fields are [consistent/inconsistent] with texture and shading • implication • fast, biologically relevant computation • real world settings require parallel processing of shading/reflection • what’s missing • priors on objects, world, inference, separation of reflection

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