[Mesa-dev] softpipe color interpolation

[Brian Paul]

On 12/19/2011 10:10 AM, Dave Airlie wrote:
> Hi guys,
>
> So we have some piglit tests
> generated_tests/spec/glsl-1.10/execution/interpolation/interpolation-none-gl_FrontColor-smooth-none.shader_test
> that piglit fails
>
> This seems to be due to its linear interpolation not producing the
> correct answers compared to the hardware, on the rendered triangle,
> there is a obvious circle of darkness that isn't there on hw rendered.
>
> Looking at tri_linear_coeff I notice a large comment explaining that
> this could be done better, llvmpipe also uses the same code, is this
> what is causing the fail?

Quite possibly.  It shouldn't be hard to hack softpipe to use 
perspective-corrected color interpolation to see if that helps.

-Brian