https://bugs.winehq.org/show_bug.cgi?id=45975
--- Comment #2 from Henri Verbeet hverbeet@gmail.com --- (In reply to Alistair Leslie-Hughes from comment #0)
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
No, that's a misunderstanding. It's clear that DepthBiasClamp is a requirement for Direct3D 10, MSDN just doesn't spell that out quite as clearly. It's also clear that the hardware is capable of the functionality, the NVIDIA legacy drivers for the GPU just don't expose that functionality because they became "legacy" before supporting the OpenGL extension.
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.
That's certainly an acceptable hack for individual users, but not something we'd want in upstream Wine.