laboratoire de physique statistique
 
 
laboratoire de physique statistique

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SPATIAL VISION 


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2008
The science and craft of autostereograms - Ninio, Jacques
SPATIAL VISION 21185-200 (2008)

Abstract : Autostereograms or SIRDS (Single Image Random-Dot Stereograms) are camouflaged stereograms which combine the Julesz random-dot stereogram principle with the wallpaper effect. They can represent any 3D shape on a single image having a quasi-periodic appearance. Rather large SIRDS can be interpreted in depth with unaided eyes. In the hands of computer graphic designers, SIRDS spread all over the world in 1992-1994, and these images, it was claimed, opened a new era of stereoscopic art. Some scientific, algorithmic and artistic aspects of these images are reviewed here. Scientifically, these images provide interesting cues on stereoscopic memory, and on the roles of monocular regions and texture boundaries in stereopsis. Algorithmically, problems arising with early SIRDS, such as internal texture repeats or ghost images are evoked. Algorithmic recommendations are made for gaining a better control on the construction of SIRDS. Problems of graphic quality (smoothness of the represented surfaces, or elimination of internal texture repeats) are discussed and possible solutions are proposed. Artistically, it is proposed that SIRDS should become less anecdotal, and more oriented towards simple geometric effects, which could be implemented on large panels in natural surrounds.
 
2007
Designing visually rich, nearly random textures - Ninio, Jacques
SPATIAL VISION 20561+ (2007)

Abstract : Camouflaging textures containing as in real life edges at all orientations, were designed by computer, then manually, for use in stereoscopic vision studies. In the manual procedure, the starting point is either a set of photographs (for instance, of barks) or a manually produced first-generation texture. Then patches are cut zigzagging and assembled into successive generations of textures. The absence of extended edges - straight or curved - and the local heterogeneity of the texture are important camouflaging factors, allowing curved surfaces to be covered with these textures without visible join. Small areas of a texture often suggest a scene, but when the areas are assembled, the suggestive power is lost, and the statistical properties of the texture then dominate. However, when symmetry is introduced (as in the Rorschach test), meaningful scenes emerge again.