[Request]: Support `lsfg-vk` frame generation

[w568w]

Tell us the problem or your need

We lack a robust, generalized frame generation solution that works across a wide range of hardwares and games.

Describe the solution you'd like

A promising, recent community effort is lsfg-vk.

In short, this project reverse-engineers and rewrites the key interface of Lossless Scaling Frame Generation (LSFG) into a pure Vulkan implementation, which allows the same frame generation algorithm to run on Linux via the DXVK.

By integrating lsfg-vk, Bottles could offer a powerful frame generation option to all users, regardless of their specific GPU vendor, complementing existing upscaling methods.

Other solutions?

Use DLSS 3/4-FG.
It only supports newer NVIDIA graphics cards and requires support from game developers.

Use AMD Fluid Motion Frames (AFMF).
It supports all games, but it is not available on Linux, and there are no plans to support it.

Use FSR 3-FG.
It requires support from game developers or mod supports.

Additional context and references

Q: How difficult would it be to integrate?
A: It's not expected to be very difficult. According to the documentation, lsfg-vk currently only consists of a few files:

~/.local/share/vulkan/explicit_layer.d/VkLayer_LS_frame_generation.json
~/.local/lib/liblsfg-vk.so

Basically a Vulkan Override Layer and its implementation. Therefore, Bottles just needs to make the Vulkan Loader load the layer to en/disable lsfg-vk. The VK_ADD_LAYER_PATH environment variable can be used to instruct it to search in non-standard locations.

However, it does require the Lossless.dll file from a legitimate copy of LSFG software. Therefore, Bottles might need to have the user configure their LSFG DLL path in the settings (under a typical Steam installation, this would be ~/.local/share/Steam/steamapps/common/Lossless Scaling/Lossless.dll).

Q: How to configure it?
A: Via environment variables. See the documentation for details.

Q: Is it unstable / highly experimental?
A: Yes. So it should be opt-in.

Q: Does it conflict with other features supported by Bottles?
A: Somewhat. For example, it is explicitly stated that it cannot support the entire Gamescope, but it does support games within Gamescope.