Hi Neil,
We still get intermittent failures with this threshold, and have
historically disabled the multisample accuracy tests in CI.
Can we relax the threshold a bit more?
-Mark
Neil Roberts <n...@linux.intel.com> writes:
> The unlit and totally_lit stats are supposed to count the pixels where
> either a primitive completely covers the pixel or no primitive touches
> it at all. However this is effectively only determined by checking
> whether any primitive has intersected one of the supersample positions
> of the reference image. It's completely possible for a primitive to
> intersect the pixel boundary but completely miss any of the
> supersample positions. The GL implementation is free to pick whatever
> multisample positions it wants within the pixel boundary so it's also
> possible for a primitive to intersect a multisample position but miss
> all of the supersample positions of the reference image. To cope with
> this this patch now allows a small margin of error for the pixels that
> are either fully lit or fully unlit.
>
> This was causing the test to give false negatives for i965 with the
> 16x MSAA positions because in that case it chooses positions that are
> exactly on the pixel boundary and these would be outside of the grid
> of positions chosen by the supersampling in the reference image. The
> positions used are actually those described by the D3D API so it is
> possible that other hardware would have the same problem.
> ---
> tests/spec/ext_framebuffer_multisample/common.cpp | 43
> +++++++++++++++++------
> 1 file changed, 33 insertions(+), 10 deletions(-)
>
> diff --git a/tests/spec/ext_framebuffer_multisample/common.cpp
> b/tests/spec/ext_framebuffer_multisample/common.cpp
> index d7be84f..fb42cc5 100644
> --- a/tests/spec/ext_framebuffer_multisample/common.cpp
> +++ b/tests/spec/ext_framebuffer_multisample/common.cpp
> @@ -530,15 +530,6 @@ Test::measure_accuracy()
> }
> }
>
> - printf("Pixels that should be unlit\n");
> - unlit_stats.summarize();
> - pass = unlit_stats.is_perfect() && pass;
> - printf("Pixels that should be totally lit\n");
> - totally_lit_stats.summarize();
> - pass = totally_lit_stats.is_perfect() && pass;
> - printf("Pixels that should be partially lit\n");
> - partially_lit_stats.summarize();
> -
> double error_threshold;
> if (test_resolve) {
> /* For depth and stencil resolves, the implementation
> @@ -558,7 +549,39 @@ Test::measure_accuracy()
> error_threshold = 0.333 *
> pow(0.6, log((double)effective_num_samples) / log(2.0));
> }
> - printf("The error threshold for this test is %f\n", error_threshold);
> +
> + /* The unlit and totally_lit stats are supposed to count the
> + * pixels where either a primitive completely covers the pixel
> + * or no primitive touches it at all. However this is
> + * effectively only determined by checking whether any
> + * primitive has intersected one of the supersample positions
> + * of the reference image. It's completely possible for a
> + * primitive to intersect the pixel boundary but completely
> + * miss any of the supersample positions. The GL
> + * implementation is free to pick whatever multisample
> + * positions it wants within the pixel boundary so it's also
> + * possible for a primitive to intersect a multisample
> + * position but miss all of the supersample positions of the
> + * reference image. To cope with this we allow a small margin
> + * of error for the pixels that are either fully lit or fully
> + * unlit.
> + */
> + double full_pixel_threshold = error_threshold * 0.05f;
> +
> + printf("Pixels that should be unlit\n");
> + unlit_stats.summarize();
> + pass = unlit_stats.is_better_than(full_pixel_threshold) && pass;
> + printf("Pixels that should be totally lit\n");
> + totally_lit_stats.summarize();
> + pass = totally_lit_stats.is_better_than(full_pixel_threshold) && pass;
> + printf("The error threshold for unlit and totally lit "
> + "pixels test is %f\n",
> + full_pixel_threshold);
> + printf("Pixels that should be partially lit\n");
> + partially_lit_stats.summarize();
> +
> + printf("The error threshold for partially lit pixels is %f\n",
> + error_threshold);
> pass = partially_lit_stats.is_better_than(error_threshold) && pass;
> // TODO: deal with sRGB.
> return pass;
> --
> 1.9.3
>
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