{"id":38131,"date":"2015-08-03T07:44:11","date_gmt":"2015-08-03T07:44:11","guid":{"rendered":"http:\/\/www.labri.fr\/perso\/barla\/blog\/?p=38131"},"modified":"2019-01-21T14:39:44","modified_gmt":"2019-01-21T14:39:44","slug":"lighting-perspective","status":"publish","type":"post","link":"https:\/\/www.labri.fr\/perso\/barla\/blog\/?p=38131","title":{"rendered":"Light field structure"},"content":{"rendered":"<p id=\"top\" \/>\n<h3 class=\"wp-block-heading\">Visual Light Field<\/h3>\n\n\n\n<p>Do we really perceive a light field in empty space? Or rather are we <strong>capable<\/strong> of adjusting a light probe so that it visually fits in its environment? The second interpretation might imply a complex task of adjustment and check, with only the latter being directly related to perception.<\/p>\n\n\n\n<p>The simpler claim that we are &#8220;merely&#8221; capable of adjusting a probe might better explain why the <strong>reconstructed<\/strong> light field (which is not necessarily perceived) lacks any rotational component: adjustment is made in direct relationship to directly (or indirectly) visible light sources, using shading patterns of other objects in close proximity.<\/p>\n\n\n\n<p>If this were to be true the reconstructed light field would come closer to the physical light field with more and more probe objects in the scene. The identification of light zones might also depend on the placement and number of objects in the scene : one could even create surprise by revealing a small isolated light zone with a properly located object.<\/p>\n\n\n\n<p>It might this be that the light field is not an end but a means to the perception of another scene property: <strong>space<\/strong>.<\/p>\n\n\n\n<p>The classification of visual light zones identification as a <strong>cognitive\u00a0<\/strong>rather than a perceptual process is supported by the observation that different subjects use different cues (shading, highlights, shadows) to adjust a light probe, and that some of these cues may be overlooked. What is <strong>perceived <\/strong>directly is rather how an object (e.g., a probe) fits in a given spatial zone (or none), which requires a concordance of many (but not all) cues: which ones?<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Lighting perspective<\/h3>\n\n\n\n<p>Pooling reflections across different nearby objects provides a cue of variation of lighting direction in space.<\/p>\n\n\n\n<p>One might approximate such variations by a cone whose apex locates the light source, with an angle similar to fov angle (fol angle?). Such a lighting perspective structure gives in turn a reliable spatial cue with large fol angles relating to near lighting in confined space, and small fol angles to distant light in open spaces.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Lighting from above<\/h3>\n\n\n\n<p>It is often assumed that lighting from above is a systematic prior (a bias?), especially in the Bayesian sense. But it could as well be a fallback prior (a default?) to help deal with ambiguous cases!<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Visual Light Field Do we really perceive a light field in empty space? Or rather are we capable of adjusting a light probe so that it visually fits in its environment? The second interpretation might imply a complex task of adjustment and check, with only the latter being directly related to perception. The simpler claim &#8230; <a title=\"Light field structure\" class=\"read-more\" href=\"https:\/\/www.labri.fr\/perso\/barla\/blog\/?p=38131\" aria-label=\"Read more about Light field structure\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[651],"tags":[],"class_list":["post-38131","post","type-post","status-publish","format-standard","hentry","category-thoughts"],"_links":{"self":[{"href":"https:\/\/www.labri.fr\/perso\/barla\/blog\/index.php?rest_route=\/wp\/v2\/posts\/38131","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.labri.fr\/perso\/barla\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.labri.fr\/perso\/barla\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.labri.fr\/perso\/barla\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.labri.fr\/perso\/barla\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=38131"}],"version-history":[{"count":7,"href":"https:\/\/www.labri.fr\/perso\/barla\/blog\/index.php?rest_route=\/wp\/v2\/posts\/38131\/revisions"}],"predecessor-version":[{"id":39857,"href":"https:\/\/www.labri.fr\/perso\/barla\/blog\/index.php?rest_route=\/wp\/v2\/posts\/38131\/revisions\/39857"}],"wp:attachment":[{"href":"https:\/\/www.labri.fr\/perso\/barla\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=38131"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.labri.fr\/perso\/barla\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=38131"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.labri.fr\/perso\/barla\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=38131"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}