[Mesa-dev] [PATCH 00/10] i965: add ARB_shader_texture_image_samples support

Francisco Jerez currojerez at riseup.net
Sun Aug 30 07:51:37 PDT 2015

Ilia Mirkin <imirkin at alum.mit.edu> writes:

> On Fri, Aug 28, 2015 at 6:58 AM, Francisco Jerez <currojerez at riseup.net> wrote:
>> Ilia Mirkin <imirkin at alum.mit.edu> writes:
>>> This should include everything. I sent a test for textureSamples to
>>> piglit a while ago, not sure how to test imageSamples -- apparently ms
>>> images aren't entirely supported on i965? But I'm not sure via what
>>> feat that happens.
>> i965 doesn't support MS images because on Gen7-8 it would involve either
>> converting all MS textures to UMS on the fly or implementing the
>> compressed MS layout in software, which would be even more madness.  On
>> Gen9 and up though it's supported natively by the hardware and it
>> shouldn't be too difficult to implement, I just haven't had the chance
>> to do the work yet.
> Yeah, I've heard that before, but... what exactly prevents one from
> using a 2DMS image? I didn't see anything that checked if the images
> were MS.
You can declare and use a multisample image uniform, but image loads
will always return zero and writes will be ignored because the image
unit state will be considered invalid (see validate_image_unit() in
shaderimage.c).  Not sure if imageSamples() is expected to do something
in particular when the image unit state is invalid, the spec doesn't
seem to be explicit about it...

>   -ilia
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