runtime/vk_fg4.cpp makes the frame generation swapchain and context with the libraries FSR 4 comes with
(amd_fidelityfx_loader_vk.dll and amd_fidelityfx_framegeneration_vk.dll beside the executable). vk_fg.cpp takes
that path only with fsr4_fg = 1 while FSR 4 is the upscaler; the default stays the FSR 3.1 library. The loader
picks the version for the card: the machine-learned FSR Frame Generation 4 on Radeon RX 9000 cards with Windows 11,
which is untested, and 3.1.6 elsewhere. On an RX 7900 XT (driver 26.10.1) it lists frame generation 3.1.6 and the
swapchains 4.0.0, which the driver brings and the loader chooses, and 3.1.7. The swapchain in place is wanted only
while its library is the one to use, so a change of the setting or of the upscaler, or a failure of this path,
takes it down as switching frame generation off does and the next present makes it with the other library.
The preparation gives this library the camera's position and axes, which FSR Frame Generation 4 requires, and a
scene scale of one metre a unit: with the 0.01 the FSR 3.1 path uses, version 3.1.6 drew grey translucent shapes
into the sky of its frames while the camera turned (160 captures of the screen during a camera sweep; clean with 1).
Both paths now generate a frame only when the picture without the HUD is there for it: generated from the
presented picture alone, the HUD would be warped with the scene behind it. In four configurations (21:9 with either
library, a 16:9 picture in a 21:9 window, a 1080 picture without HDR) every generated frame had it, and the log
counts the frames without. On screen, of the 6,404 pixels of the HUD's item button that stayed fixed through a
camera sweep with the FSR 3.1 library, 6,162 stayed fixed with this one.
Standing in Hyrule Field at 3440x1440 with FSR 4 Quality the game draws 43.0 frames a second with this path and
42.2 with the FSR 3.1 library, each shown twice over. One run changed the present mode, HDR, fullscreen, frame
generation, FSR 4, this setting and the upscaler in turn: 216 screenshots without a bad frame, and no failure.
The SDK's frame generation headers join runtime/third_party/ffx_sdk, unmodified. tools/make_kit.py and
tools/make_launcher.py take the third library from the --ffx4 folder when it is there, and tools/make_game.py
copies it beside the game.
Co-Authored-By: Claude Fable 5.2 <noreply@anthropic.com>
