[Piglit] [PATCH] New testsuite for ARB_color_buffer_float (v2)

Marek Olšák maraeo at gmail.com
Sun Aug 29 22:34:54 PDT 2010

This is a cool set of tests so I've pushed this. If there happens to be
anything wrong with it, we'll fix it.


On Thu, Aug 26, 2010 at 5:19 PM, Luca Barbieri <luca at luca-barbieri.com>wrote:

> This in an updated version of the test I posted, now split into 8 tests
> sharing a common header file.
> It now features testing of multiple render targets and fog.
> Test output logs and results on GeForce 8xxx, GTX 2xx or ideally GTX 4xx
> with the proprietary drivers would be really welcome.
> The files are put in "spec/arb_color_buffer_float" with the idea of
> starting a convention of writing testsuites for each new extension
> to be implemented in Mesa, putting it in "spec/<extension_name>".
> The tests now fail on any bugs in the default mode.
> If "-xfail" is passed, then known bugs on ATI and nVidia will be ignored,
> and all tests will then succeed.
> The driver bugs don't seem due (solely) to hardware limitations, but may
> be due to software fallbacks being improperly implemented.
> There are two areas where the specification seems unclear, as far as I
> understand it.
> I'm not sure what the process to ask for clarification is, and suggestions
> would be welcome here.
> This first issue is whether, when fragment clamping is set to FIXED_ONLY
> and the FBO has some fixed-point and some floating-point buffers attached,
> gl_FragData[n] is never clamped, or is clamped only for the fixed point
> buffers.
> Note that while blending on fixed-point clamps the color anyway, alpha
> test and polygon smoothing happen before blending, and should be affected
> by whether gl_FragData[n] is clamped or not.
> From the OpenGL 4.1 spec, it seems that the intent is that fragment
> clamping does not depend on the target, especially because it can be
> bound dynamically due to user-defined varyings.
> None of the hardware I have access to supports such dishomogeneous FBOs,
> so I have no idea what the proprietary drivers do.
> Current nVidia cards might shed light on this.
> The second issue is whether disabling fragment clamping disables the
> clamping done before fog application in fragment shaders with ARB_fog_*
> options (or whether this is undefined)
> This happens in the fixed pipeline, but making it happen for shaders too
> would contradict the rationale of adding ARB_fog_* to shaders, which
> is to avoid recompilation.
> All the hardware I have access to has fixed function fog (all existing
> Radeons seem to have it), and here the disabling applies to fragment
> programs too, as a "naive" implementation would result in.
> Again, current nVidia cards might shed light on this.
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