[Piglit] [PATCH] Transform feedback: Modify tessellation test to verify primitive count.

[Paul Berry]

On 27 December 2011 13:03, Eric Anholt <eric at anholt.net> wrote:

> On Mon, 19 Dec 2011 15:52:35 -0800, Paul Berry <stereotype441 at gmail.com>
> wrote:
> > This patch modifies the transform feedback tessellation test to check
> > that the query GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN counts the
> > correct number of primitives for all primitive types.  Previously, we
> > were only testing correct behavior of GL_TRANSFORM_FEEDBACK_PRIMITIVES
> > in the "position" test, which always draws triangles.
> >
> > Verified that these tests still pass on the nVidia proprietary Linux
> > driver.
> > ---
> >
> > This patch depends on "[PATCH v3] Add a test of tessellation of
> > transform feedback primitives.", which is still under review on the
> > Piglit mailing list, pending an investigation into why some of the
> > tests fail on an AMD system.
>
> This test seems like a relevant one to be testing the primitives
> queries.  But why only WRITTEN and not GENERATED as well?
>

Just trying to save myself some time.  Prior to this patch, we already had
tests that verify that when drawing GL_TRIANGLES, there is agreement among
GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN, GL_PRIMITIVES_GENERATED, and the
number of vertices written into the transform feedback buffer.  And the
tessellation test already verified that the correct number of vertices were
written into the transform feedback buffer in all drawing modes.  That
really should be adequate for verifying correct operation on most
hardware.  However, on Mesa i965, since we implement the
GL_TRANSFORM_FEEDBACK_PRIMITIVES and GL_PRIMITIVES_GENERATED queries in
software, it was important to test that the software path for counting
vertices was correct in all drawing modes.  Since Mesa i965 uses the same
software path for computing GL_TRANSFORM_FEEDBACK_PRIMITIVES and
GL_PRIMITIVES_GENERATED, I know that this test is adequate for testing Mesa
i965.

I am still discovering and fixing transform feedback bugs on Mesa i965, so
making the tests perfect isn't my top priority yet.  Once I've written all
the tests I need, and fixed all the bugs they discover, I'll loop back and
revise patches like this one.
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