[Mesa-dev] [PATCH 2/2] glsl: set user defined varyings to smooth by default

[Ian Romanick]

On 02/15/2016 07:12 AM, Iago Toral wrote:
> On Mon, 2016-02-15 at 18:38 +1100, Timothy Arceri wrote:
>> This is usually handled by the backends in order to handle the
>> various interactions with the gl_*Color built-ins.
>>
>> The problem is this means linking will fail if one side on the
>> interface adds the smooth qualifier to the varying and the other
>> side just uses the default even though they match.
>>
>> This fixes various deqp tests and should have no impact on
>> built-ins as they generate GLSL IR directly.
>>
>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92743
>> ---
>>  src/compiler/glsl/ast_to_hir.cpp | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/src/compiler/glsl/ast_to_hir.cpp b/src/compiler/glsl/ast_to_hir.cpp
>> index b639378..47d52ee 100644
>> --- a/src/compiler/glsl/ast_to_hir.cpp
>> +++ b/src/compiler/glsl/ast_to_hir.cpp
>> @@ -2750,6 +2750,11 @@ interpret_interpolation_qualifier(const struct ast_type_qualifier *qual,
>>                            "vertex shader inputs or fragment shader outputs",
>>                            interpolation_string(interpolation));
>>        }
>> +   } else if ((mode == ir_var_shader_in &&
>> +               state->stage != MESA_SHADER_VERTEX) ||
>> +              (mode == ir_var_shader_out &&
>> +               state->stage != MESA_SHADER_FRAGMENT)) {
>> +      interpolation = INTERP_QUALIFIER_SMOOTH;
>>     }
> 
> The GLES spec explicitly says that in the absence of an interp qualifier
> smooth is used, but I can't find the same statement in the desktop GLSL
> spec. Should we make this ES specific?

Desktop OpenGL has an API control (via glShadeModel) that OpenGL ES 2.0+
does not have.  If a compatibility profile vertex shader outputs
built-in varyings (or maybe just color... I'd have to look) to
fixed-function, the interpolation mode is determined by the shading
model (GL_FLAT or GL_SMOOTH).

> Iago
> 
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