GL_EXT_provoking_vertex http://www.opengl.org/registry/specs/EXT/provoking_vertex.txt GL_EXT_provoking_vertex GL_QUADS_FOLLOW_PROVOKING_VERTEX_CONVENTION_EXT 0x8E4C GL_FIRST_VERTEX_CONVENTION_EXT 0x8E4D GL_LAST_VERTEX_CONVENTION_EXT 0x8E4E GL_PROVOKING_VERTEX_EXT 0x8E4F void glProvokingVertexEXT (GLenum mode)