ARB_shading_language_packing is part of GLSL 4.2, not 4.0 as I mistakenly believed. The following functions are available only with ARB_shading_language_packing, GLSL 4.2 (not GLSL 4.0), or ES 3.0: - packSnorm2x16 - unpackSnorm2x16 - packHalf2x16 - unpackHalf2x16 Reviewed-by: Carl Worth <cworth@cworth.org> Reviewed-by: Marek Olšák <marek.olsak@amd.com>