{"id":40204,"date":"2019-12-03T07:27:16","date_gmt":"2019-12-03T07:27:16","guid":{"rendered":"http:\/\/www.labri.fr\/perso\/barla\/blog\/?p=40204"},"modified":"2019-12-03T07:33:50","modified_gmt":"2019-12-03T07:33:50","slug":"scales-textures","status":"publish","type":"post","link":"https:\/\/www.labri.fr\/perso\/barla\/blog\/?p=40204","title":{"rendered":"Scales &#038; textures"},"content":{"rendered":"<p id=\"top\" \/>\n<h3 class=\"wp-block-heading\">A grasp at scales<\/h3>\n\n\n\n<p>Hard to keep an intuition of scale in nature, useful to characterize  which optical theories apply correctly. From angstrom to mm, find series of examples (atoms, cells, scratches,  etc) to illustrate each range. Provide a list of theories in optics that properly deal with matter at each scale range. <br>Characterize distance to elements based on angular resolution of some  humans and animals. Point out that there are more theories to be discovered, at small but also middle scales ! <\/p>\n\n\n\n<h3 class=\"wp-block-heading\">IOR isolines&amp; scales<\/h3>\n\n\n\n<p>Start at the molecular level (solids, liquids, gazes) and how different structures impact light propagation; summarized in refractive index.  Isolines around strong gradients bring out surfaces at the microscopic  level, constituting minute elements of form.<br>When transitioning to the image scale, the notion of surface may be hard  to preserve&#8230; First the gradient may not have everywhere the same strength; hence when  seen not distant enough, the surface may &#8220;evaporate&#8221;. This may happen in any kind of substrate, like in clouds, foam on  watter, even dust on solids! Many IOR isolines may also clutter inside a single sensel (pixel\/RF),  such as with fur, leaves, hairs, etc. <br>Some cases are less problematic, such as when the surface is optically  smooth or at least with a surface roughness that conforms to IOR isolines. In general, IOR gradients are strong for all wavelengths at once, but when plunged in a medium of similar IOR, it may even vary with colors  (fuzzy forms?) <\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Discrete structured volumes<\/h3>\n\n\n\n<p>Trees, bushes, fur, grass, crop, hairs, present (low-frequency) light-  and view-dependent patterns. They emerge most clearly when seen from sufficiently afar, but are found at multiple scales. <br>They depend on the correlation between position and orientation of  discrite elements w.r.t. the global structure. These in turn characterize how they reflect\/transmit light when visible  from outside light sources <br>Examples: olive trees, velvet, towels, hairy leaves, etc. <\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Textured gloss<\/h3>\n\n\n\n<p>Visual textures behave differently with respect to light and view in  static and dynamic configurations. <br>Flakes in a binder do not remove reflected light in the center of the  highlight region, while they add flanking glittery textures. They turn on and off with changing light or view direction, giving the  impression to follow the highlight from a distance. They disappear in diffuse lighting, leaving only low-frequency shading  patterns due to shadowing (diffuse &#8220;coarseness&#8221;). <br>Bumps and dents on a surface will remove some of the reflectied light in  the center of the highlight region. This might be due to inter-reflections, especially in concave  micro-structures (dents). Their flanking glitter effect tends to be more pronounced (check), maybe  because of some contrast effect? Their diffuse behavior is also likely to be more high-frequency, but  this should be checked as well&#8230; <br>Pigmentation mainly brings variations in colors, but maybe some examples  of shininess variations could be found? <\/p>\n","protected":false},"excerpt":{"rendered":"<p>A grasp at scales Hard to keep an intuition of scale in nature, useful to characterize which optical theories apply correctly. From angstrom to mm, find series of examples (atoms, cells, scratches, etc) to illustrate each range. Provide a list of theories in optics that properly deal with matter at each scale range. Characterize distance &#8230; <a title=\"Scales &#038; textures\" class=\"read-more\" href=\"https:\/\/www.labri.fr\/perso\/barla\/blog\/?p=40204\" aria-label=\"Read more about Scales &#038; textures\">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":[772],"tags":[],"class_list":["post-40204","post","type-post","status-publish","format-standard","hentry","category-blog"],"_links":{"self":[{"href":"https:\/\/www.labri.fr\/perso\/barla\/blog\/index.php?rest_route=\/wp\/v2\/posts\/40204","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=40204"}],"version-history":[{"count":4,"href":"https:\/\/www.labri.fr\/perso\/barla\/blog\/index.php?rest_route=\/wp\/v2\/posts\/40204\/revisions"}],"predecessor-version":[{"id":40208,"href":"https:\/\/www.labri.fr\/perso\/barla\/blog\/index.php?rest_route=\/wp\/v2\/posts\/40204\/revisions\/40208"}],"wp:attachment":[{"href":"https:\/\/www.labri.fr\/perso\/barla\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=40204"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.labri.fr\/perso\/barla\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=40204"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.labri.fr\/perso\/barla\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=40204"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}