title: Lighting, backlighting and watercolor illusions and the laws of figurality.
abstract: We report some novel 'lighting' and 'backlighting' effects in plane figures similar to those which induce the 'watercolor illusion', that is, figures made with outlines composed of juxtaposed parallel lines varying in brightness and chromatic color. These new effects show 'illumination' as an emergent percept, and show how arrangements of 'dark and light' along the boundaries of various plane figures model the volume and strengthen the illusion of depth. To account for these various effects we propose several phenomenological 'laws of figurality' to add to the Gestalt laws of organization and figure-ground segregation. We offer a set of meta-laws which are speculative but which serve to integrate and organize the phenomenological laws. These laws indicate how luminance gradient profiles across boundary contours define both the 3D appearance of figures and the properties of the light reflected from their volumetric shapes.
authors.affiliation: Department of Sciences of Languages, University of Sassari, via Roma 151, 1-07100, Sassari, Italy. baingio@uniss.it
authors.forename: Baingio
authors.initials: B
authors.lastname: Pinna
authors.forename: Adam
authors.initials: A
authors.lastname: Reeves
mesh_terms: D000221:Adaptation, Ocular / Q000502:physiology*; D003118:Color Perception / Q000502:physiology*; D006801:Humans; D007088:Illusions / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D012016:Reference Values