[Mesa-dev] [PATCH 02/11] mesa: add ARB_gpu_shader_fp64 extension info

[Dave Airlie]

On 23 August 2014 10:55, Ian Romanick <idr at freedesktop.org> wrote:
> On 08/14/2014 03:52 AM, Dave Airlie wrote:
>> From: Dave Airlie <airlied at redhat.com>
>>
>> This just adds the entries to extensions.c and mtypes.h
>>
>> Signed-off-by: Dave Airlie <airlied at redhat.com>
>> ---
>>  src/mesa/main/extensions.c | 1 +
>>  src/mesa/main/mtypes.h     | 1 +
>>  2 files changed, 2 insertions(+)
>>
>> diff --git a/src/mesa/main/extensions.c b/src/mesa/main/extensions.c
>> index 4f322d0..1445a9d 100644
>> --- a/src/mesa/main/extensions.c
>> +++ b/src/mesa/main/extensions.c
>> @@ -117,6 +117,7 @@ static const struct extension extension_table[] = {
>>     { "GL_ARB_framebuffer_sRGB",                    o(EXT_framebuffer_sRGB),                    GL,             1998 },
>>     { "GL_ARB_get_program_binary",                  o(dummy_true),                              GL,             2010 },
>>     { "GL_ARB_gpu_shader5",                         o(ARB_gpu_shader5),                         GL,             2010 },
>> +   { "GL_ARB_gpu_shader_fp64",                     o(ARB_gpu_shader_fp64),                     GL,             2010 },
>>     { "GL_ARB_half_float_pixel",                    o(dummy_true),                              GL,             2003 },
>>     { "GL_ARB_half_float_vertex",                   o(ARB_half_float_vertex),                   GL,             2008 },
>>     { "GL_ARB_instanced_arrays",                    o(ARB_instanced_arrays),                    GL,             2008 },
>
> The extension spec says, "OpenGL 3.2 and GLSL 1.50 are required."  Many
> times these requirements are excessive... and there just because people
> didn't want to think about the interactions with older versions. :)  In
> this case, however, I think it's reasonable.  In GLSL 1.50 the rules
> about where interpolation qualifiers were specified changed.  The last
> bit of issue 9 alludes to this.
>
>     (9) Are double-precision "varyings" (values passed between shader stages)
>         supported by this extension?  If so, is double-precision interpolation
>         is supported?
>
>       RESOLVED:  Double-precision shader inputs and outputs are supported,
>       except for vertex shader inputs and fragment shader outputs.
>       Additionally, double-precision vertex shader inputs are provided by the
>       separate extension EXT_vertex_attrib_64bit.  No known extension provides
>       double-precision fragment outputs, but that doesn't seem important since
>       OpenGL provides no pixel/texture formats with double-precision
>       components that could reasonably receive such outputs.
>
>       Interpolation not supported in this extension for double-precision
>       floating-point components.  As with integer types in OpenGL 3.0,
>       double-precision floating-point fragment shader inputs must be qualified
>       as "flat".
>
>       Note that this extension reformulates the spec language requiring "flat"
>       qualifiers, in addition to adding doubles to the list of "flat" types.
>       In GLSL 1.30, the spec applies these requirements to vertex shader
>       outputs but imposes no requirement on fragment inputs.  We move this
>       requirement to fragment inputs, since vertex shader outputs may be
>       passed to tessellation or geometry shaders without interpolation, and
>       thus without the need for qualification by "flat".
>
> Because of this, it seems like we should restrict this extension to
> core profile.  Opinions?

Yes I'm happy to restrict to GL core, seems like it would cause less
possible issues.

Dave.