Re: [PATCH 6/6] wined3d: Set z = 0.0 via the projection matrix instead of depth clamping.

[Matteo Bruni]

2015-02-11 21:53 GMT+01:00 Stefan Dösinger <stefan(a)codeweavers.com>:
> This works on cards that don't implement ARB_depth_clamp like r500
> cards.
>
> Note that texturing is influenced by position.w, not position.z.
> ---
>  dlls/wined3d/directx.c    |  7 -------
>  dlls/wined3d/state.c      | 33 ++++++++++-----------------------
>  dlls/wined3d/wined3d_gl.h |  2 --
>  3 files changed, 10 insertions(+), 32 deletions(-)

It's probably hard to measure and not going to really matter in
practice but toggling the depth clamping (where supported) might be
slightly faster than updating the projection matrix.
I'm not NACKing the patch though.

[PATCH 6/6] wined3d: Set z = 0.0 via the projection matrix instead of depth clamping.

[Stefan Dösinger]

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Am 2015-02-11 um 23:56 schrieb Matteo Bruni:
> It's probably hard to measure and not going to really matter in 
> practice but toggling the depth clamping (where supported) might
> be slightly faster than updating the projection matrix.
> I'll try to patch my drawprim overhead tester to test this.

I don't expect it to be faster though. At very least it depends on the
game's behavior. One of two switches that needs to be toggled to
disable depth clipping is switching to POSITIONT vertices, in which
case we update the projection matrix anyway.

Even if there's a minor performance advantage of depth clamping in
cases where an application constantly uses POSITIONT and switches
ZENABLE on an off I prefer to always use the projection matrix to have
only one codepath that does this. If there's a huge difference we may
think about two alternating codepaths.

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[PATCH 6/6] wined3d: Set z = 0.0 via the projection matrix instead of depth clamping.

[Stefan Dösinger]

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Am 2015-02-12 um 08:45 schrieb Stefan Dösinger:
> Am 2015-02-11 um 23:56 schrieb Matteo Bruni:
> > It's probably hard to measure and not going to really matter in 
> > practice but toggling the depth clamping (where supported) might 
> > be slightly faster than updating the projection matrix.
> > I'll try to patch my drawprim overhead tester to test this.
> > Fwiw, I cannot see any performance difference between ARB_depth_clamp
> > and the projection matrix approach in my modified test program.

What I did:
Set a POSITIONT vertex

while(running)
{
    for(i = 0; i < 1000; i++)
    {
        set_rs(ZENABLE, TRUE);
        draw();
        set_rs(ZENABLE, FALSE);
        draw();
        set_rs(ZENABLE, TRUE);
        draw();
        set_rs(ZENABLE, FALSE);
        draw();
        set_rs(ZENABLE, TRUE);
        draw();
        set_rs(ZENABLE, FALSE);
        draw();
    }
    present();
}

I.e., I hit the worst case for the new approach. With ARB_depth_clamp
this test program runs at 89.5 fps, with matrices at 89.2. There seems
to be a general up and down of +/- 5 fps. Interestingly windows runs
this test program at 58 fps.

I tested this on Nvidia. I can also test it on r600g if desired, but I
don't really expect it to matter.
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