[Mesa-dev] [PATCH] meta: Use result of texture coordinate clamping operation

[Anuj Phogat]

On Wed, Sep 9, 2015 at 6:19 PM, Ian Romanick <idr at freedesktop.org> wrote:
> On 09/09/2015 04:55 PM, Anuj Phogat wrote:
>> On Wed, Sep 9, 2015 at 11:30 AM, Ian Romanick <idr at freedesktop.org>
wrote:
>>> I'm pretty sure our implementation of this extension is complete
>>> rubbish.  I have attached an image from the blit-scaled test.  This
>>> result cannot be useful to anyone.
>>>
>> Paul Berry and I agreed to follow the "NVIDIA Implementation Details"
>> given in the extension spec. i965 driver currently use bilinear filtering
>> for both SCALED_RESOLVE_FASTEST and SCALED_RESOLVE_NICEST.
>> Do you think the implementation doesn't match what is suggested in
>> the spec? I'll be happy to work on improving the implementation if you
>> have any specific comments.
>>
>> Extension spec mentions the potential loss of quality when using a
>> single pass scaled resolve blit. Also the quality of image generated
>> depends on sample count and scaling factor. I vaguely remember
>> Paul mentioned the scaling factor of ~1.5, beyond which single pass
>> scaled resolve blit quickly becomes useless. I think the attached
>> image is using a scaling factor of 2.4.
>
> Yes, I think so.  It was the last image produced by the test.
>
>> I'm attaching an old image generated by me doing the quality
>> comparison with Nvidia's proprietary driver implementation. I posted
>> the image on mesa-dev before enabling the extension on i965. Please
>> see the images under "New implementation" for the comparison.
>
> Comparing our images with NVIDIA's image, I don't see very much
> difference.  That's both reassuring and depressing.  Looking at all of
> those images, I can't imagine why anyone would bother using this
> functionality.  I doubt there's any scenario where the little "spikes"
> that grow of the sides of the triangles is acceptable.  Oh well.

Markus Wick (IRC name: degasus) shared these dolphin emulator
images (rendered using i965 drivers) with me on dri-devel. They show
the effect of using the extension over resolve and liner scaling. I think
most of the images look crisper with little loss of smooth edges.
https://www.dropbox.com/sh/vmt7tolzd6qlnpo/AABlGkXZ4W6_ucFk0Gk3tfNpa?dl=0
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