Abstract
Human observers group local shading patterns into global super-patterns that appear to be illuminated in some unitary fashion. Many years ago, this was noticed for the case of uniform, unidirectional illumination. Recently, we found that it also applies to convergent and divergent illumination flows, but that human observers are blind to rotational light flow patterns (in the sense of being unable to group the local shading patterns). We now report that human observers are also blind to deformation patterns. This is perhaps interesting because convergent, divergent, rotational, and deformation patterns all occur in natural light fields. This is an idiosyncrasy of the human visual system, on par with the fact that visual awareness fails to present the observer with saddle shapes.
Highlights
The conventional stimulus(1) in shape from shading research for about a century has been a circular disk filled with a linear intensity gradient (Metzger, 1975; Ramachandran, 1988a, 1988b)
We report that human observers are blind to deformation patterns
This is perhaps interesting because convergent, divergent, rotational, and deformation patterns all occur in natural light fields
Summary
The conventional stimulus(1) in shape from shading research for about a century has been a circular disk filled with a linear intensity gradient (Metzger, 1975; Ramachandran, 1988a, 1988b). It represents most likely an attempt to catch the essential information in shading patterns, which is supposed to be the first-order intensity variation in a small neighborhood about a point (Turhan, 1935). Not just the intensity gradient determines the resulting perception, the circular outline is just as important (a square outline yields a very different perception; Wagemans, van Doorn, & Koenderink, 2010). This basic pattern has been adopted in a large volume of research, which is the reason why we used it in the present study (Figure 1). Most observers report that the basic stimulus appears to them as a pictorial relief, modulated in depth. Observers who report a depth articulation declare to see either a “cap” (convexity, like the outside of an eggshell) or a “cup”
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
