[Bug 45975] New: DirectX 10 games no longer work with nVidia legacy driver.

[wine-bugs at winehq.org]

https://bugs.winehq.org/show_bug.cgi?id=45975

            Bug ID: 45975
           Summary: DirectX 10 games no longer work with nVidia legacy
                    driver.
           Product: Wine
           Version: unspecified
          Hardware: x86
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: directx-d3d
          Assignee: wine-bugs at winehq.org
          Reporter: leslie_alistair at hotmail.com
      Distribution: ---

42b5d88f2e081d90195bd3cd1931929f84b26f45
Author: Zebediah Figura <z.figura12 at gmail.com>  2018-10-09 05:25:39

    wined3d: Implement depth bias clamp.

    Based on a patch by Michael Müller.

    Signed-off-by: Zebediah Figura <z.figura12 at gmail.com>
    Signed-off-by: Henri Verbeet <hverbeet at codeweavers.com>
    Signed-off-by: Alexandre Julliard <julliard at winehq.org>

The change "gl_info->supported[ARB_POLYGON_OFFSET_CLAMP]" added by Henri
during his review which is causing the issue.

+    if (gl_info->supported[WINED3D_GL_VERSION_3_2]
+            && gl_info->supported[ARB_POLYGON_OFFSET_CLAMP]
+            && gl_info->supported[ARB_SAMPLER_OBJECTS])

I have a nVidia 8600 GT and 9600 GT which are both capable of running many
DirectX 10 games however now they wont run under wine since the driver doesn't
have ARB_POLYGON_OFFSET_CLAMP support.

The legacy driver doesn't have any other functions which could be used as a
replacement for ARB_POLYGON_OFFSET_CLAMP.

Using glView, from Realtech VR, shows that the 8600 GT doesn't support
ARB_POLYGON_OFFSET_CLAMP or infact any of the 4.6 standard GL functions.  Maybe
DirectX does Depth Bias Clamping internally if the card doesn't support it or
maybe its part of the 10.1+ standard.  No-one know for sure.

As Henri pointed out, it's not clear that Deapth Bais Clamping is actually a
requirement for DirectX 10 but is rather implied based off
https://docs.microsoft.com/en-us/windows/desktop/direct3d11/d3d10-graphics-programming-guide-output-merger-stage-depth-bias

It's now my understanding that if Depth Bais Clamping isn't supported then we
may end up with minor Artefacts in some places, for some games.  I'm sure users
can live with a little glitch now and again, if it means they can play games
that they know their hardware is perfectly capable of running.

There is an option to use the nouveau driver to workaround the issue, however
for me this driver performs extremely badly when playing native games.

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