Kelsidavis-WoWee/docs/AMD_FSR2_INTEGRATION.md

# AMD FSR2 Integration Notes

WoWee supports two FSR2 backends at runtime:

- `AMD FidelityFX SDK` backend (preferred when available).
- `Internal fallback` backend (used when AMD SDK prerequisites are not met).

## SDK Location

AMD SDK checkout path:

`extern/FidelityFX-FSR2`

FidelityFX SDK checkout path (framegen extern):

`extern/FidelityFX-SDK` (default branch `main` from WoWee's fork in build scripts and CI)

Override knobs for local build scripts:

- `WOWEE_FFX_SDK_REPO` (default: `https://github.com/Kelsidavis/FidelityFX-SDK.git`)
- `WOWEE_FFX_SDK_REF` (default: `main`)

Detection expects:

- `extern/FidelityFX-FSR2/src/ffx-fsr2-api/ffx_fsr2.h`
- `extern/FidelityFX-FSR2/src/ffx-fsr2-api/vk/shaders/ffx_fsr2_accumulate_pass_permutations.h`
- If permutation headers are missing in the SDK checkout, WoWee CMake copies a vendored snapshot from:
  - `third_party/fsr2_vk_permutations`

## Build Flags

- `WOWEE_ENABLE_AMD_FSR2=ON` (default): attempt AMD backend integration.
- `WOWEE_ENABLE_AMD_FSR3_FRAMEGEN=ON` (default): build AMD FSR3 framegen interface probe when FidelityFX-SDK headers are present.
- `WOWEE_HAS_AMD_FSR2` compile define:
  - `1` when AMD SDK prerequisites are present.
  - `0` when missing, in which case internal fallback remains active.
- `WOWEE_HAS_AMD_FSR3_FRAMEGEN` compile define:
  - `1` when FidelityFX-SDK FI/OF/FSR3+VK headers are detected.
  - `0` when headers are missing (probe target disabled).

Runtime note:

- Renderer/UI expose a persisted experimental framegen toggle.
- Runtime loader is Path A only (official AMD runtime library).
- Path A runtime build now auto-runs `tools/generate_ffx_sdk_vk_permutations.sh` to ensure required VK permutation headers exist for FSR2/FSR3 upscaler shader blobs.
- You can point to an explicit runtime binary with:
  - `WOWEE_FFX_SDK_RUNTIME_LIB=/absolute/path/to/libffx_fsr3_vk.so` (or `.dll` / `.dylib`).
- If no official runtime is found, frame generation is disabled cleanly (Path C).


## Current Status

- AMD FSR2 Vulkan dispatch path is integrated and used when available.
- UI displays active backend in settings (`AMD FidelityFX SDK` or `Internal fallback`).
- Runtime settings include persisted FSR2 jitter tuning.
- FidelityFX-SDK extern is fetched across platforms (default: `Kelsidavis/FidelityFX-SDK` on `main`).
- Startup safety behavior remains enabled:
  - persisted FSR2 is deferred until `IN_WORLD`
  - startup falls back unless `WOWEE_ALLOW_STARTUP_FSR2=1`

## FSR Defaults

- Quality default: `Native (100%)`
- UI quality order: `Native`, `Ultra Quality`, `Quality`, `Balanced`
- Default sharpness: `1.6`
- Default FSR2 jitter sign: `0.38`
- Performance preset is intentionally removed.

## CI Notes

- `build-linux-amd-fsr2` clones AMD's repository and configures with `WOWEE_ENABLE_AMD_FSR2=ON`.
- All build jobs clone:
  - `GPUOpen-Effects/FidelityFX-FSR2` (`master`)
  - `Kelsidavis/FidelityFX-SDK` (`main`) by default
- Linux CI validates FidelityFX-SDK Kits framegen headers:
  - `upscalers/fsr3/include/ffx_fsr3upscaler.h`
  - `framegeneration/fsr3/include/ffx_frameinterpolation.h`
  - `framegeneration/fsr3/include/ffx_opticalflow.h`
  - `backend/vk/ffx_vk.h`
- Runtime build path auto-bootstrap:
  - Linux downloads DXC automatically when missing.
  - Windows (MSYS2) downloads DXC automatically when missing.
  - macOS expects `dxc` to be available in `PATH` (CI installs it via Homebrew).
- CI builds `wowee_fsr3_framegen_amd_vk_probe` when that target is generated by CMake for the detected SDK layout.
- Some upstream SDK checkouts do not include generated Vulkan permutation headers.
- WoWee bootstraps those headers from the vendored snapshot so AMD backend builds remain cross-platform and deterministic.
- If SDK headers are missing entirely, WoWee still falls back to the internal backend.