[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"doc-detail-148374-en":3,"doc-seo-148374-105":30,"detail-sidebar-cat-0-en-105":94},{"code":4,"msg":5,"data":6},0,"success",{"doc_id":7,"user_id":8,"nickname":9,"user_avatar":10,"doc_module":4,"category_id":11,"category_name":12,"doc_title":13,"doc_description":14,"doc_content":15,"file_id":16,"file_url":17,"file_type":18,"file_size":19,"view_count":4,"is_deleted":4,"is_public":20,"is_downloadable":20,"audit_status":20,"page_count":21,"language":22,"language_code":23,"site_id":24,"html_lang":23,"table_of_contents":25,"faqs":26,"seo_title":27,"seo_description":14,"update_tm":28,"read_time":29},148374,549768702563,"Fahsai","https://ap-avatar.wpscdn.com/avatar/8000c4aa63b76e948b?x-image-process=image/resize,m_fixed,w_180,h_180&k=1786536092046926083",6,"Technology","Point-Based Hair Global Illumination - sketch","Point-based representation enables global illumination effects in Tangled hair, focusing on occlusion and indirect lighting around animated characters. The work addresses missing ambient occlusion and color bleeding integration in the existing hair shader while keeping artist usability and rendering practicality. It describes generating a compact, accurate hair pointcloud from dense curve data, then filtering points via a radius-based vector field so expensive global illumination computation includes only relevant surface/discontinuity regions.","Point-based Hair Global Illumination (sketches_posters_ 0175)  \nRamón Montoya-Vozmediano  \nWalt Disney Animation Studios*  \nFigure 1: (a) Final render and (b) ambient occlusion component (© Disney Enterprises)  \nAbstract  \nA point-based representation was extensively used on Tangled to generate occlusion and indirect illumination involving the characters' hair . We describe how this was achieved in reasonable rendering times .  \n1 Motivation  \nThe hair shader on Tangled takes into account the effects needed to make hair believable such as inter-strand scattering or secondary reflections . It is also specifically designed to be very intuitive to use by artists [Sadeghi et al. 2010] . However, we did not have a solution for ambient occlusion and color bleeding to and from the hair . Those components are essential for lighters to integrate the hair into the scene, a task further complicated by the fact that the shader also provides a highly realistic look while living in a world of stylized materials. Because of this a robust solution to computing global illumination involving the hair was needed.  \nIn general, for Tangled we precompute global illumination using a point-based representation of the scene's surfaces that then  \n* email: [ramon.montoya@disney.com](ramon.montoya@disney.com)  \nbecomes the input to RenderMan's ptfilter (a standalone program that uses pointclouds to precompute global illumination effects) . For hair the problem is how to extract a representation that is accurate enough for closeups but compact enough to prevent filtering times from drastically increasing.  \n2 Hair Representation  \nAs the hair travels along the production pipeline a number of representations are used. For visualization purposes, the hair for Rapunzel and other characters is represented as a surface . However, the real shape of the hair is encoded from animation to simulation and to final render using an increasing set of curves with an ever increasing amount of control points to accommodate the detail that each production step adds . What is initially 10 curves with 100 control points will become tens of thousands of curves with up to 2400 control points for the renderer .  \nFor the hair occlusion to be believable, a hard surface representation cannot be used, as it introduces a harsh discontinuity between the skin and the hair itself. Similarly, while ambient occlusion is soft and featureless away from the hair it brings out small details on an object's surface very clearly (cf. figure 1b) . This means we need to start with the most accurate hair representation and filter it afterwards .  \nThe simplest solution would be to use a pointcloud storing all of the hair's control points. This is very costly, since we want indirect illumination effects from and to the hair, but also between the different parts of the hair represented in the pointcloud. All of the points in the pointcloud would be taken into account in these computations and that would be prohibitively expensive . Hence, we will only include initially a uniformly decimated percentage of all control points, and then simplify the hair pointcloud based on a user specified parameter that will take away unnecessary points only, either because they are deep inside the volume or because they are already represented by nearby data.  \n3 Hair Pointcloud Filtering  \nTo do so, we randomly (but consistently across frames) bake into the pointcloud 10 to 20% of the final render hair curves, and for each one of those curves we store approximately 1 point for every 3 pixels on screen . These points are stored in a kd-tree for faster processing as they typically range in the millions . The user specifies a radius R that determines the minimum size of features in the hair that need to be preserved in the final pointcloud. Each point generates a vectorial field pointing away from it that dies off at a distance R [Blinn 1982] . Then, for each point in the pointcloud we add up all repelling vectors .","cbCaintLQax5R3pa","https://ap.wps.com/l/cbCaintLQax5R3pa","pdf",6808023,1,2,"English","en",105,"# Motivation\n# Hair Representation\n# Hair Pointcloud Filtering\n# Practical Considerations","[{\"question\":\"What global illumination components were missing for Tangled hair?\",\"answer\":\"Ambient occlusion and color bleeding to and from the hair were not solved, even though they are essential for integrating hair into the scene.\"},{\"question\":\"How does the method keep hair pointclouds compact for rendering?\",\"answer\":\"Instead of storing all hair control points, it initially keeps a uniformly decimated subset and then further simplifies the pointcloud based on a user-specified radius that removes redundant points.\"},{\"question\":\"How does the filtering determine whether a point should be kept?\",\"answer\":\"Each point accumulates repelling vectors from nearby hair samples; a near-zero resultant indicates the point lies inside the hair volume, while non-zero vectors point toward discontinuities or internal density changes.\"},{\"question\":\"Why are normals added to the hair points?\",\"answer\":\"Using the accumulated vectors as normals adds cosine falloff so ambient occlusion has proper high-frequency contrast without breaking the believability of the underlying hair shader.\"}]","Point-Based Hair Global Illumination - sketch | PDF",1787779431,5,{"code":4,"msg":31,"data":32},"ok",{"site_id":24,"language":23,"slug":33,"title":13,"keywords":34,"description":14,"schema_data":35,"social_meta":89,"head_meta":91,"extra_data":93,"updated_unix":28},"point-based-hair-global-illumination-sketch","",{"@graph":36,"@context":88},[37,53,67],{"@type":38,"itemListElement":39},"BreadcrumbList",[40,44,47,50],{"item":41,"name":42,"@type":43,"position":20},"https://docshare.wps.com","Home","ListItem",{"item":45,"name":46,"@type":43,"position":21},"https://docshare.wps.com/document/","Document",{"item":48,"name":12,"@type":43,"position":49},"https://docshare.wps.com/document/technology/",3,{"item":51,"name":13,"@type":43,"position":52},"https://docshare.wps.com/document/point-based-hair-global-illumination-sketch/148374/",4,{"url":51,"name":13,"@type":54,"author":55,"headline":13,"publisher":57,"fileFormat":60,"inLanguage":23,"description":14,"dateModified":61,"datePublished":61,"encodingFormat":60,"isAccessibleForFree":62,"interactionStatistic":63},"DigitalDocument",{"name":9,"@type":56},"Person",{"url":41,"name":58,"@type":59},"DocShare","Organization","application/pdf","2026-08-26",true,{"@type":64,"interactionType":65,"userInteractionCount":4},"InteractionCounter",{"@type":66},"ViewAction",{"@type":68,"mainEntity":69},"FAQPage",[70,76,80,84],{"name":71,"@type":72,"acceptedAnswer":73},"What global illumination components were missing for Tangled hair?","Question",{"text":74,"@type":75},"Ambient occlusion and color bleeding to and from the hair were not solved, even though they are essential for integrating hair into the scene.","Answer",{"name":77,"@type":72,"acceptedAnswer":78},"How does the method keep hair pointclouds compact for rendering?",{"text":79,"@type":75},"Instead of storing all hair control points, it initially keeps a uniformly decimated subset and then further simplifies the pointcloud based on a user-specified radius that removes redundant points.",{"name":81,"@type":72,"acceptedAnswer":82},"How does the filtering determine whether a point should be kept?",{"text":83,"@type":75},"Each point accumulates repelling vectors from nearby hair samples; a near-zero resultant indicates the point lies inside the hair volume, while non-zero vectors point toward discontinuities or internal density changes.",{"name":85,"@type":72,"acceptedAnswer":86},"Why are normals added to the hair points?",{"text":87,"@type":75},"Using the accumulated vectors as normals adds cosine falloff so ambient occlusion has proper high-frequency contrast without breaking the believability of the underlying hair shader.","https://schema.org",{"og:url":51,"og:type":90,"og:title":13,"og:site_name":58,"og:description":14},"article",{"robots":92,"canonical":51},"index,follow",{"doc_id":7,"site_id":24},{"code":4,"msg":5,"data":95},[96,100,104,108,112,115,120,125,130,133,137],{"id":20,"doc_module":4,"doc_module_name":46,"category_name":97,"show_sort_weight":98,"slug":99},"Story & Novel",90,"story-novel",{"id":21,"doc_module":4,"doc_module_name":46,"category_name":101,"show_sort_weight":102,"slug":103},"Literature",80,"literature",{"id":52,"doc_module":4,"doc_module_name":46,"category_name":105,"show_sort_weight":106,"slug":107},"Exam",70,"exam",{"id":29,"doc_module":4,"doc_module_name":46,"category_name":109,"show_sort_weight":110,"slug":111},"Comic",60,"comic",{"id":11,"doc_module":4,"doc_module_name":46,"category_name":12,"show_sort_weight":113,"slug":114},50,"technology",{"id":116,"doc_module":4,"doc_module_name":46,"category_name":117,"show_sort_weight":118,"slug":119},7,"Healthcare",40,"healthcare",{"id":121,"doc_module":4,"doc_module_name":46,"category_name":122,"show_sort_weight":123,"slug":124},8,"Research & Report",30,"research-report",{"id":126,"doc_module":4,"doc_module_name":46,"category_name":127,"show_sort_weight":128,"slug":129},9,"Religion & Spirituality",20,"religion-spirituality",{"id":128,"doc_module":4,"doc_module_name":46,"category_name":131,"show_sort_weight":128,"slug":132},"World Cup","world-cup",{"id":134,"doc_module":4,"doc_module_name":46,"category_name":135,"show_sort_weight":134,"slug":136},10,"Lifestyle","lifestyle",{"id":138,"doc_module":4,"doc_module_name":46,"category_name":139,"show_sort_weight":29,"slug":140},19,"General","general"]