[Piglit] [PATCH] fbo-blending-snorm: new test for testing snorm blend behavior

[Eric Anholt]

sroland at vmware.com writes:

> From: Roland Scheidegger <sroland at vmware.com>
>
> The existing fbo-blending-formats test is mostly useless for anything but
> unorm formats, since it does not test any values outside [0,1] (neither for
> src, dst, intermeidate calculations, blend result).
> I tried to enhance it but it got too complex, in particular because I really
> want to test snorm, not floats (which aren't really validated much neither),
> because if you actually use int math for them it's difficult to handle and
> llvmpipe had lots of bugs. And it's not even obvious from the GL spec when
> clamping actually happens (in particular, the inverse blend factors will be
> in range [0,2]). snorm blending is sort of semi-supported in GL, the
> presence of EXT_texture_snorm doesn't guarantee it (and nvidia doesn't support
> the extension, presumably because they can't or don't want to deal with the
> legacy alpha/luminance/intensity formats), and while GL 3.1 introduces the
> snorm formats too it isn't guaranteed for rendering neither (for GLES OTOH
> there's a EXT_render_snorm extension), so the format handling of the
> fbo-blending-formats test isn't really sufficient and not easily extensible.
> So, this test will test actual blend behavior with values which will need
> clamping, and where the intermediate and final values will be negative (and,
> for the inverse blend factors, be even larger than one).
> This passes (now) on llvmpipe, and nvidia blob. softpipe is a complete
> failure (if there's clamping it will always clamp to [0,1] for starters),
> and as a matter of fact, softpipe doesn't get the clamping right even with
> unorm neither, since values outside [0,1] won't get clamped in the tile
> cache when there's no clamping, hence they'll enter the blend later when
> blend is enabled unclamped - but there's no test for this (note this is
> only an issue if the fragment color clamp is disabled).

I thought the ARB_color_buffer_float/render test was trying to cover
this.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 832 bytes
Desc: not available
URL: <https://lists.freedesktop.org/archives/piglit/attachments/20171122/96f2297b/attachment-0001.sig>