Am 05.01.2017 um 20:43 schrieb Samuel Pitoiset: > > > On 01/05/2017 06:49 PM, Roland Scheidegger wrote: >> Meh, I'm not really a big fan of such hacks. GPUs have support for NaNs >> since ages, and while glsl is lenient the point stands that returning a >> NaN is a more correct result, so doing extra work to get a wrong result >> doesn't look all that great to me. >> FWIW dx10 requires NaNs as results (for both sqrt and rsq). Maybe app >> specific quirks (if said apps can't be fixed) would be better... >> But well, it's your driver, so whatever floats your boat. > > I think the main idea here is to reduce the number of bug reports when > applications use D3D-style for RSQ/SQRT instead of what GLSL spec says.
Well if someone ports from d3d10, he might well expect NaNs since d3d10 guarantees you get a NaN there... (That said, with d3d10 NaNs will get converted to zeros on pixel shader export if the RT isn't a float type, I don't know what mesa drivers to there.) Not saying it wouldn't make sense doing such hackery at glsl level but imho it still should be a quirk. Roland >> >> Roland >> >> >> Am 05.01.2017 um 18:37 schrieb Marek Olšák: >>> Shouldn't we also use abs for SQRT? For example, this adds abs for >>> both RSQ and SQRT: >>> >>> https://urldefense.proofpoint.com/v2/url?u=https-3A__cgit.freedesktop.org_-7Emareko_mesa_commit_-3Fid-3D5e0fb661a8e6ac5f7b2245dd31595155128e0664&d=DgIGaQ&c=uilaK90D4TOVoH58JNXRgQ&r=_QIjpv-UJ77xEQY8fIYoQtr5qv8wKrPJc7v7_-CYAb0&m=wUYi2DhIZXHwD19wGIoEgceIF0cE0chTe7swjZ4MLVs&s=ZqrwtvXGdvXw-YJQtVnWo7yBeH5lhM3jtnYaa6vFZJY&e= >>> >>> >>> Marek >>> >>> On Thu, Jan 5, 2017 at 5:47 PM, Samuel Pitoiset >>> <samuel.pitoi...@gmail.com> wrote: >>>> As explained by Nicolai, it seems like D3D always compute the >>>> absolute value while GLSL says that the result of inversesqrt() >>>> is undefined if x <= 0. Using the absolute value looks like safer >>>> especially when the game has been ported from D3D to GL. >>>> >>>> This gets rid of the NaN values in the "Spec Ops: The Line" game >>>> as well as the black squares. >>>> >>>> Bugzilla: >>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__bugs.freedesktop.org_show-5Fbug.cgi-3Fid-3D97338&d=DgIGaQ&c=uilaK90D4TOVoH58JNXRgQ&r=_QIjpv-UJ77xEQY8fIYoQtr5qv8wKrPJc7v7_-CYAb0&m=wUYi2DhIZXHwD19wGIoEgceIF0cE0chTe7swjZ4MLVs&s=gjxDxmhEtQDYO34rucXJ6nIDojabOhpTAx1rNUP6X-g&e= >>>> >>>> >>>> Signed-off-by: Samuel Pitoiset <samuel.pitoi...@gmail.com> >>>> --- >>>> >>>> Nouveau also computes the absolute value before emitting RSQ. >>>> >>>> src/gallium/drivers/radeonsi/si_shader_tgsi_alu.c | 9 ++++++--- >>>> 1 file changed, 6 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/src/gallium/drivers/radeonsi/si_shader_tgsi_alu.c >>>> b/src/gallium/drivers/radeonsi/si_shader_tgsi_alu.c >>>> index 1966752cc0..ec6d6b0534 100644 >>>> --- a/src/gallium/drivers/radeonsi/si_shader_tgsi_alu.c >>>> +++ b/src/gallium/drivers/radeonsi/si_shader_tgsi_alu.c >>>> @@ -754,9 +754,12 @@ static void emit_rsq(const struct >>>> lp_build_tgsi_action *action, >>>> struct lp_build_tgsi_context *bld_base, >>>> struct lp_build_emit_data *emit_data) >>>> { >>>> - LLVMValueRef sqrt = >>>> - lp_build_emit_llvm_unary(bld_base, TGSI_OPCODE_SQRT, >>>> - emit_data->args[0]); >>>> + LLVMValueRef abs, sqrt; >>>> + >>>> + abs = lp_build_emit_llvm_unary(bld_base, TGSI_OPCODE_ABS, >>>> + emit_data->args[0]); >>>> + >>>> + sqrt = lp_build_emit_llvm_unary(bld_base, TGSI_OPCODE_SQRT, >>>> abs); >>>> >>>> emit_data->output[emit_data->chan] = >>>> lp_build_emit_llvm_binary(bld_base, TGSI_OPCODE_DIV, >>>> -- >>>> 2.11.0 >>>> >>>> _______________________________________________ >>>> mesa-dev mailing list >>>> mesa-dev@lists.freedesktop.org >>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.freedesktop.org_mailman_listinfo_mesa-2Ddev&d=DgIGaQ&c=uilaK90D4TOVoH58JNXRgQ&r=_QIjpv-UJ77xEQY8fIYoQtr5qv8wKrPJc7v7_-CYAb0&m=wUYi2DhIZXHwD19wGIoEgceIF0cE0chTe7swjZ4MLVs&s=boy8sEj2W3FP0LnjHsSnUxWrR98aM22Qq-uxvFIqMlQ&e= >>>> >>> _______________________________________________ >>> mesa-dev mailing list >>> mesa-dev@lists.freedesktop.org >>> https://urldefense.proofpoint.com/v2/url?u=https-3A__lists.freedesktop.org_mailman_listinfo_mesa-2Ddev&d=DgIGaQ&c=uilaK90D4TOVoH58JNXRgQ&r=_QIjpv-UJ77xEQY8fIYoQtr5qv8wKrPJc7v7_-CYAb0&m=wUYi2DhIZXHwD19wGIoEgceIF0cE0chTe7swjZ4MLVs&s=boy8sEj2W3FP0LnjHsSnUxWrR98aM22Qq-uxvFIqMlQ&e= >>> >>> >> _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
