[Mesa-dev] [PATCH 26/35] meta: Use common GLSL code for blits

[Rogovin, Kevin]

Hi,

> We can't do stencil blits with GLSL because no driver that uses meta can
> do the GL_ARB_shader_stencil_export extension.  For depth and color
> blits, we can always write the values from the shader, and disable
> writes to the buffers using glColorMask and glDepthMask.  So... we just
> need one shader.

Should we add GL_ARB_shader_stencil_export as one of the extensions Mesa
can support? Naturally that is major tangent from this, and I am not too sure
what hardware beyond newer AMD hardware has that capability.

The shader had that the fragment depth used the same value as the red of the
fragment color, so should it not be then 3 shaders (color only, depth only, color and depth)
with the last one having two samplers?

Also, should not the case of blitting from MSAA to non-MSAA be handled correctly?
i.e. use the sampler type sampler2DMS  and average over the number of samples?
or possible fancier filtering kernels?

Best Regards,
 -Kevin Rogovin
________________________________________
From: Ian Romanick [idr at freedesktop.org]
Sent: Sunday, February 02, 2014 5:45 PM
To: Rogovin, Kevin; mesa-dev at lists.freedesktop.org
Subject: Re: [Mesa-dev] [PATCH 26/35] meta: Use common GLSL code for blits

On 01/30/2014 09:51 AM, Rogovin, Kevin wrote:
>> @@ -487,6 +486,7 @@ setup_shader_for_sampler(struct gl_context *ctx, struct glsl_sampler
>> *sampler)
>>                                   "void main()\n"
>>                                  "{\n"
>>                                  "   gl_FragColor = %s(texSampler, %s);\n"
>> +                                  "   gl_FragDepth = gl_FragColor.x;\n"
>
> *IF* I understood what this is to do, is to provide FBO blit API
> implementation from upstairs mesa. Should not a different shader be used
> base on the 8 possibilities(really 7 since all 0 means no-op) of the
> bits being up and down: COLOR_BUFFER_BIT, DEPTH_BUFFER_BIT and
> STENCIL_BUFFER_BIT ? The above looks like to me to handle either
> COLOR_BUFFER_BIT or DEPTH_BUFFER_BIT up, but not both. With that in mind
> then there would be up to 3 separate samplers (one for color, one for
> stencil and one for depth).

We can't do stencil blits with GLSL because no driver that uses meta can
do the GL_ARB_shader_stencil_export extension.  For depth and color
blits, we can always write the values from the shader, and disable
writes to the buffers using glColorMask and glDepthMask.  So... we just
need one shader.

> Or am I missing something?
>
> -Kevin
>
>
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