[Bug 99339] Blender line rendering broken after removing XY clipping of lines

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=99339

Kenneth Graunke <kenneth at whitecape.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #5 from Kenneth Graunke <kenneth at whitecape.org> ---
Should be fixed by:

commit ece0e535a44c228dd994861592deb155c14740d8
Author: Kenneth Graunke <kenneth at whitecape.org>
Date:   Wed Jan 11 21:38:52 2017 -0800

    i965: Always scissor on Gen6-7.5 instead of disabling guardband.

    Previously we disabled the guardband when the viewport was smaller than
    the framebuffer on Gen6-7.5, to prevent portions of primitives from
    being draw outside of the viewport.  On Gen8+, we relied on the viewport
    extents test to effectively scissor this away for us.

    We can simply always enable scissoring instead.  We already include the
    viewport in the scissor rectangle, so this will effectively do the
    viewport extents test for us.  (The only difference is that the scissor
    rectangle doesn't support sub-pixel values.  I think that's okay.)

    Given that the viewport extents test is essentially a second scissor,
    and is enabled for basically all 3D drawing on Gen8+, it stands to
    reason that scissoring is cheap.  Enabling the guardband reduces the
    cost of clipping, which is expensive.

    The Windows driver appears to never disable guardband clipping, and
    appears to use scissoring in this case.  I don't know if they leave
    it on universally though.

    This fixes misrendering in Blender, where the "floor plane" grid lines
    started rendering at wrong angles after I disabled XY clipping of line
    primitives.  Enabling the guardband seems to solve the issue.

    Cc: "17.0" <mesa-stable at lists.freedesktop.org>
    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99339
    Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
    Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>

or at least the series including that.  This will be in Mesa 17.0.

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