[Piglit] GL_LIGHTING test

[Michal Suchanek]

On 12 August 2010 00:11, Brian Paul <brianp at vmware.com> wrote:
> On 08/11/2010 10:01 AM, Michal Suchanek wrote:
>>
>> Hello
>>
>> I experience issues with some 3D applications rendering odd (too
>> bright) on a r600.
>>
>> Going through mesa demos I noticed that GL_LIGHTING produces different
>> result on r600 than other cards making the bright area larger.
>>
>> I wrote a test that checks for this difference.
>>
>> For me it fails on r600, r600g and llvmpipe and succeeds on swrast. It
>> should also succeed on r300 or i915 which render the demo much like
>> swrast but I did not actually run the test on them.
>>
>> The test can be found at
>> http://repo.or.cz/w/piglit/hramrach.git/shortlog/refs/heads/wip
>>
>> I would like to get a test for this issue into piglit so that it's
>> easy to check.
>>
>> If the test is inadequate please specify how it should be improved.
>
> I took a quick look and it appears that gallium/softpipe/llvmpipe are
> correct but swrast is wrong.  NVIDIA's driver agrees with gallium too.
>
> I think the issue is the light source is positioned behind the object so
> there should be no diffuse contribution to the final color.  I don't know
> why swrast (tnl, actually) is producing non-zero diffuse lighting in this
> case.
>

AFAICT the light source is in front of the object. If it were behind
the whole object would be dark.

Or is there something I am missing?

Thanks

Michal