GL_SGIS_texture_lod http://www.opengl.org/registry/specs/SGIS/texture_lod.txt GL_SGIS_texture_lod GL_TEXTURE_MIN_LOD_SGIS 0x813A GL_TEXTURE_MAX_LOD_SGIS 0x813B GL_TEXTURE_BASE_LEVEL_SGIS 0x813C GL_TEXTURE_MAX_LEVEL_SGIS 0x813D