{"id":701,"date":"2011-09-08T12:33:35","date_gmt":"2011-09-08T11:33:35","guid":{"rendered":"http:\/\/www.ozone3d.net\/blogs\/lab\/?p=701"},"modified":"2015-05-05T20:48:20","modified_gmt":"2015-05-05T19:48:20","slug":"tutorial-opengl-3-3-sampler-states-configurer-unites-de-texture","status":"publish","type":"post","link":"https:\/\/www.ozone3d.net\/blogs\/lab\/20110908\/tutorial-opengl-3-3-sampler-states-configurer-unites-de-texture\/","title":{"rendered":"Les Sampler States OpenGL 3.3: Configurer les Unit\u00e9s de Texture"},"content":{"rendered":"<p><center><\/p>\n<p><img decoding=\"async\" src=\"http:\/\/www.ozone3d.net\/public\/jegx\/201109\/msi_kombustor_tessy_sphere.jpg\" alt=\"MSI Kombustor, tessellated sphere, DoF and soft shadows\" \/><\/p>\n<p><\/center><\/p>\n<p><!--more--><\/p>\n<p>Je viens de tester les sampler states disponibles avec <b>OpenGL 3.3<\/b> dans Kombustor 2.2.x. Les samplers states servent tout simplement \u00e0 d\u00e9finir l&#8217;\u00e9tat d&#8217;une unit\u00e9 de texture, ind\u00e9pendamment de l&#8217;objet texture qui y est appliqu\u00e9. Les sampler states sont d\u00e9crits dans cette spec OpenGL: <a href=\"http:\/\/www.opengl.org\/registry\/specs\/ARB\/sampler_objects.txt\">GL_ARB_sampler_objects<\/a>.<\/p>\n<p>Chose int\u00e9ressante, les sampler states OpenGL 3.3 permettent de coller \u00e0 la logique de <b>Direct3D 11<\/b> qui d\u00e9finit aussi cette abstraction hardware avec la structure <b>D3D11_SAMPLER_DESC<\/b> et les fonctions CreateSamplerState (device D3D11) et PSSetSamplers (contexte immediat). Avant OpenGL 3.3, l&#8217;\u00e9tat d&#8217;une unit\u00e9 de texture \u00e9tait li\u00e9 \u00e0 un objet texture (cr\u00e9\u00e9 avec glGenTextures). Maintenant avec les sampler states, on s&#8217;approche du niveau hardware \/ GPU. <\/p>\n<p>Voyons rapidement comment utiliser les sampler states. <\/p>\n<p><b>1 &#8211; Cr\u00e9ation et initialisation du sampler:<\/b><\/p>\n<pre lang=\"c\" line=\"1\">\r\nGLuint sampler_state = 0;\r\nglGenSamplers(1, &sampler_state);\r\nglSamplerParameteri(sampler_state, GL_TEXTURE_WRAP_S, GL_REPEAT);\r\nglSamplerParameteri(sampler_state, GL_TEXTURE_WRAP_T, GL_REPEAT);\r\nglSamplerParameteri(sampler_state, GL_TEXTURE_MAG_FILTER, GL_LINEAR);\r\nglSamplerParameteri(sampler_state, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);\r\nglSamplerParameterf(sampler_state, GL_TEXTURE_MAX_ANISOTROPY_EXT, 16.0f);\r\n<\/pre>\n<p>Je viens de cr\u00e9er un sampler state de filtrage lin\u00e9aire avec X16 de filtrage anisotropique. Les param\u00e8tres sont les m\u00eames que ceux utilis\u00e9s lors de la cr\u00e9ation d&#8217;une texture.<\/p>\n<p><b>2 &#8211; Utilisation du sampler<\/b><\/p>\n<pre lang=\"c\" line=\"1\">\r\nGLuint texture_unit = 0;\r\nglBindSampler(texture_unit, sampler_state);\r\n...\r\n<\/pre>\n<p>Rien de plus simple: il suffit de dire sur quelle unit\u00e9 de texture doit on appliquer notre sampler. Une fois appliqu\u00e9 sur une unit\u00e9 de texture, les r\u00e9glages du sampler sont prioritaires \u00e0 ceux d&#8217;un objet de texture. Donc c&#8217;est super simple d&#8217;ajouter les sampler states dans votre code OpenGL. Pas besoin de modifier le code existant de cr\u00e9ation des textures.<\/p>\n<p>Quand on ne veut plus utiliser un sampler sur une unit\u00e9 de texture, il suffit d&#8217;appeller le code suivant:<\/p>\n<pre lang=\"c\" line=\"1\">\r\nglBindSampler(texture_unit, 0);\r\n<\/pre>\n<p><b>3 &#8211; Destruction du sampler:<\/b><\/p>\n<pre lang=\"c\" line=\"1\">\r\nglDeleteSamplers(1, &sampler_state);\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9,8],"tags":[477,638,365,476,204,214],"class_list":["post-701","post","type-post","status-publish","format-standard","hentry","category-opengl","category-programming","tag-gl_arb_sampler_objects","tag-opengl","tag-programmation","tag-sampler","tag-texture","tag-tutorial"],"aioseo_notices":[],"views":2060,"_links":{"self":[{"href":"https:\/\/www.ozone3d.net\/blogs\/lab\/wp-json\/wp\/v2\/posts\/701","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.ozone3d.net\/blogs\/lab\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ozone3d.net\/blogs\/lab\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ozone3d.net\/blogs\/lab\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ozone3d.net\/blogs\/lab\/wp-json\/wp\/v2\/comments?post=701"}],"version-history":[{"count":0,"href":"https:\/\/www.ozone3d.net\/blogs\/lab\/wp-json\/wp\/v2\/posts\/701\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.ozone3d.net\/blogs\/lab\/wp-json\/wp\/v2\/media?parent=701"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ozone3d.net\/blogs\/lab\/wp-json\/wp\/v2\/categories?post=701"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ozone3d.net\/blogs\/lab\/wp-json\/wp\/v2\/tags?post=701"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}