[Mesa-dev] EXT_gpu_shader4 glsl

Ian Romanick idr at freedesktop.org
Wed Sep 14 12:18:39 PDT 2011

Hash: SHA1

On 09/14/2011 12:18 PM, Dave Airlie wrote:
>>> Hi guys,
>>> So I've been noticing there are a number of inconsistencies 
>>> between EXT_gpu_shader4 and GLSL1.30, are you planning on 
>>> implementing EXT_gpu_shader4?
>>> EXT_gpu_shader4 appears to define "unsigned" and can also use 
>>> texture2D to sample from integer samplers.
>> There are a few functional differences between GLSL 1.30 and 
>> EXT_gpu_shader4.  At the very least, EXT_gpu_shader4 supports
>> TexBOs and UBOs.  I think there are a couple other things as
>> well.  We're targeting GLSL 1.30 and OpenGL 3.0 in the next major
>> release, so there will really only be a short period where we
>> have one but not the other in Mesa master.
>> I think that we may fill-in some of the missing EXT_gpu_shader4
>> bits after GLSL 1.30 is done.  My plan was for that to primarily
>> be a vehicle to get the simpler / older TexBO and UBO extensions
>> working as we work towards GLSL 1.40.
>>> My main worry is we end up needing GL3.0 entrypoints when we
>>> are missing float texture for example, so we would want to
>>> expose EXT_gpu_shader4 then I suppose, but then we would want
>>> to fix up the GLSL handling for it.
>> What do you mean?
> Some of us can't ship advertising GL3.0, it would be nice if that 
> didn't make life harder for apps that don't require all the GL3.0 
> features but just want EXT_gpu_shader4 type features. If we don't 
> advertise GL3.0 we won't get all the new entry points unless we 
> advertise EXT_gpu_shader4.

That's part of my confusion.  The EXT_gpu_shader4 entry points are
different from the GL 3.0 entry points.  At this point, I don't think
there are any (at least not many) apps that will use the
EXT_gpu_shader4 entry points.  Apps will check for OpenGL 3.0 and will
call glXGetProcAddress on glUniform4uiv, not glUniform4uivEXT.  Right?
 I see the problem, I just don't see how EXT_gpu_shader4 actually helps.
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