attrib[4 * index + 0].normal = pos[0];
attrib[4 * index + 0].tex_coord[0] = 0.0f;
attrib[4 * index + 0].tex_coord[1] = tex_v_begin;
attrib[4 * index + 0].tex_coord[2] = tex;
attrib[4 * index + 0].normal = pos[0];
attrib[4 * index + 0].tex_coord[0] = 0.0f;
attrib[4 * index + 0].tex_coord[1] = tex_v_begin;
attrib[4 * index + 0].tex_coord[2] = tex;