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

[Timothy Arceri]

On 13/05/17 00:11, John Brooks wrote:
> On Fri, May 12, 2017 at 03:56:26PM +0200, Samuel Pitoiset wrote:
>>
>>
>> On 05/12/2017 03:39 PM, 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
>>>
>>> These patches make the compiler more lenient so that the shaders compile.
>>> Because such redeclarations are not explicitly valid in the spec, this
>>> behaviour is selectively activated by the new allow_glsl_builtin_redeclaration
>>> driconf option, which has been enabled for both games in the default drirc.
>>>
>>> With this change, both games work on Mesa and render correctly. Note that the
>>> games require OpenGL 4.4+, and so it is necessary to launch them with
>>> MESA_GL_VERSION_OVERRIDE and MESA_GLSL_VERSION_OVERRIDE set to OpenGL 4.4 (GLSL
>>> 440) or higher.
>>>
>>> Contrary to popular belief, this problem actually had nothing whatsoever to do
>>> with compatibility profiles. Forcing Mesa to create a higher version
>>> compatibility profile with MESA_GL_VERSION_OVERRIDE=4.5COMPAT or
>>> allow_higher_compat_version results in graphical glitches, so don't use that.
>>
>> I wonder if there is multiple versions of Dying Light, but using
>> MESA_GL_VERSION_OVERRIDE=4.4 and MESA_GLSL_VERSION_OVERRIDE=440 doesn't work
>> for me (game crash at launching). Also it requests some unsupported GL
>> functions (compat?).
>>
>> IIRC, Dying Light wants a GL 4.4 compat profile, I guess Timothy can
>> confirm?
>>
>> What's your steam app ID?
>>
>> Btw, you probably don't need to override the GL/GLSL versions, it should be
>> backward compatible.
>>
> 
> Steam App ID 239140. The use of legacy functions (such as glBegin) in frame 0
> is SDL's doing:
> <https://github.com/spurious/SDL-mirror/blob/master/src/render/opengl/SDL_render_gl.c#L1334>
> 
> I don't know why your game would crash on launch. My first thought would be
> steam runtime issues though. Make sure Steam runtime is enabled and remove
> ~/.local/share/Steam/ubuntu12_32/steam-runtime/amd64/usr/lib/x86_64-linux-gnu/libstdc++.so.6
> 
> The version override is necessary since the game will not render at all with a
> 3.0 compat profile, which is what it gets without an override.

Right but isn't that is because the game is requesting a compat profile?

How do you know that the rendering issues you see when using the compat 
override are not because of missing compat support for higher GL versions?

For example a feature/behavior supported in an eariler GL version may 
have been changed to be more like core and it just happens that 
overriding to use core makes the rendering problems go away.

> 
> --
> John Brooks
> Frogging101 on IRC and elsewhere
>