Monday, October 18, 2021

vkd3d-proton version 2.5 has been released

VKD3D-Proton is a fork of VKD3D, which aims to implement the full Direct3D 12 API on top of Vulkan. The project serves as the development effort for Direct3D 12 support in Proton.


This is a release with a little bit of everything!


DXR progress

DXR has seen significant work in the background.

  • DXR 1.1 is now experimentally exposed. It can be enabled with VKD3D_CONFIG=dxr11.
    Note that DXR 1.1 cannot be fully implemented in VK_KHR_ray_tracing's current form, in particular
    DispatchRays() indirect is not compatible yet,
    although we have not observed a game which requires this API feature.
  • DXR 1.1 inline raytracing support is fully implemented.
  • DXR 1.0 support is more or less feature complete.
    Some weird edge cases remain, but will likely not be implemented unless required by a game.
    VKD3D_CONFIG=dxr will eventually be dropped when it matures.

Some new DXR games are starting to come alive, especially with DXR 1.1 enabled,
but there are significant bugs as well that we currently cannot easily debug.
Some experimental results on NVIDIA:

  • Control - already worked
  • DEATHLOOP - appears to work correctly
  • Cyberpunk 2077 - DXR can be enabled, but GPU timeouts
  • World of Warcraft - according to a user, it works, but we have not confirmed ourselves
  • Metro Exodus: Enhanced Edition -
    gets ingame and appears to work? Not sure if it looks correct.
    Heavy CPU stutter for some reason ...
  • Metro Exodus (original release) - GPU timeouts when enabling DXR
  • Resident Evil: Village - Appears to work, but the visual difference is subtle.

It's worth experimenting with these and others.
DXR is incredibly complicated, so expect bugs.
From here, DXR support is mostly a case of stamping out issues one by one.


NVIDIA contributed integration APIs in vkd3d-proton which enables DLSS support in D3D12 titles in Proton.
See Proton documentation for how to enable NvAPI support.

Shader models

A fair bit of work went into DXIL translation support to catch up with native drivers.

  • Shader model 6.5 is exposed.
    Shader model 6.6 should be straight forward once that becomes relevant.
  • Shader model 6.4 implementation takes advantage of VK_KHR_shader_integer_dot_product when supported.
  • Proper fallback for FP16 math on GPUs which do not expose native FP16 support (Polaris, Pascal).
    Notably fixes AMD FSR shaders in Resident Evil: Village (and others).
  • Shader model 6.1 SV_Barycentric support implemented (NVIDIA only for now).
  • Support shader model 6.2 FP32 denorm control.


Resizable BAR can improve GPU performance about 10-15% in the best case, depends a lot on the game.
Horizon Zero Dawn and Death Stranding in particular improve massively with this change.

By default, vkd3d-proton will now take advantage of PCI-e BAR memory types through heuristics
as D3D12 does not expose direct support for resizable BAR, and native D3D12 drivers are known to use heuristics as well.
Without resizable BAR enabled in BIOS/vBIOS, we only get 256 MiB which can help performance,
but many games will improve performance even more
when we are allowed to use more than that.
There is an upper limit for how much VRAM is dedicated to this purpose.
We also added VKD3D_CONFIG=no_upload_hvv to disable all uses of PCI-e BAR memory.

Other performance improvements:

  • Avoid redundant descriptor update work in certain scenarios (NVIDIA contribution).
  • Minor tweaks here and there to reduce CPU overhead.

Fixes and workarounds

  • Fix behavior for swap chain presentation latency HANDLE. Fixes spurious deadlocks in some cases.
  • Fix many issues related to depth-stencil handling, which fixed various issues in DEATHLOOP, F1 2021, WRC 10.
  • Fix DIRT 5 rendering issues and crashes. Should be fully playable now.
  • Fix some Diablo II Resurrected rendering issues.
  • Workaround shader bugs in Psychonauts 2.
  • Workaround some Unreal Engine 4 shader bugs which multiple titles trigger.
  • Fix some stability issues when VRAM is exhausted on NVIDIA.
  • Fix CPU crash in boot-up sequence of Far Cry 6 (game is still kinda buggy though, but gets in-game).
  • Fix various bugs with host visible images. Fixes DEATHLOOP.
  • Fix various DXIL conversion bugs.
  • Add Invariant geometry workarounds for specific games which require it.
  • Fix how d3d12.dll exports symbols to be more in line with MSVC.
  • Fix some edge cases in bitfield instructions.
  • Work around extreme CPU memory bloat on the specific NVIDIA driver versions which had this bug.
  • Fix regression in Evil Genius 2: World Domination.
  • Fix crashes in Hitman 3.
  • Fix terrain rendering in Anno 1800.
  • Various correctness and crash fixes.

 Link to source code

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