[Mesa-dev] [PATCH 0/2] Allow redeclaration of GLSL builtins; fixes Dying Light and Dead Island Definitive Edition

[John Brooks]

On 05/15/2017 06:52 PM, John Brooks wrote:
> On 2017-05-15 06:04 PM, Ian Romanick wrote:
>> On 05/12/2017 06:39 AM, John Brooks wrote:
>>> Since release, Dying Light and Dead Island Definitive Edition have 
>>> been broken
>>> on Mesa, producing at best only a black screen after loading. I 
>>> found that the
>>> root of the problem is that their vertex shaders redeclare the GLSL 
>>> builtin
>>> gl_VertexID, which Mesa's compiler considers to be an error:
>>>
>>>      error: `gl_VertexID' redeclared
>> Sorry for not responding to this sooner.  I've been away for the last
>> few weeks.
>>
>> I believe that we enforce this as the result of a conformance test that
>> does almost exactly this thing.  We didn't used to enforce it, but after
>> discussion with Khronos (which I can dig up), we began enforcing it.
>> This also led to a clarification in the GLSL spec.  Section 3.7
>> (Identifiers) of the GLSL 4.50 spec says:
>>
>>     However, as noted in the specification, there are some cases where
>>     previously declared variables can be redeclared, and predeclared
>>     "gl_" names are allowed to be redeclared in a shader only for these
>>     specific purposes. More generally, it is a compile-time error to
>>     redeclare a variable, including those starting “gl_”.
>>
>> Redeclaring gl_VertexID is clearly a bug in the game.  Has anyone
>> reported this to them?
>>
>> _______________________________________________
>> mesa-dev mailing list
>> mesa-dev at lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/mesa-dev
> I posted this on the Steam forums:
> http://steamcommunity.com/app/239140/discussions/0/1326718197205660517/#c1326718197205867749 
>
>
> I'll put what I wrote there in a support ticket on 
> support.techland.pl. If
> we're lucky maybe they'll do something about it, though I'm not 
> terribly optimistic.
>
> -- 
> John Brooks (Frogging101)

Response to my support ticket:

 > Thank you for your feedback, it has been passed to our dev team. Keep 
in mind
 > that some ideas might not be implemented in our game.

So we'll see what happens I guess. Probably good to have this fix on the 
Mesa
side at least for now, in case they don't end up fixing it.

--
John Brooks (Frogging101)