[Mesa-dev] softpipe color interpolation

[Dave Airlie]

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?

Dave.