Add wrapper backend mode switch and explicit DX12 bridge runtime errors

README.md

@@ -208,6 +208,9 @@ make -j$(nproc)
   - In-tree wrapper build:
     - `wowee_fsr3_vk_wrapper` now builds automatically when FSR3 SDK headers are present and outputs to `build/bin/libffx_fsr3_vk_wrapper.*`.
     - Wrapper backend override (what the wrapper loads underneath): `WOWEE_FSR3_WRAPPER_BACKEND_LIB=/absolute/path/to/libffx_fsr3_vk.so`.
+    - Wrapper backend mode:
+      - `WOWEE_FSR3_WRAPPER_BACKEND=vulkan_runtime` (default on non-Windows)
+      - `WOWEE_FSR3_WRAPPER_BACKEND=dx12_bridge` (default on Windows; bridge dispatch wiring still in progress)
   - Path B wrapper libraries must export the clean wrapper ABI (`include/rendering/amd_fsr3_wrapper_abi.h`):
     - `wowee_fsr3_wrapper_get_abi_version`
     - `wowee_fsr3_wrapper_initialize`

docs/AMD_FSR2_INTEGRATION.md

@@ -52,6 +52,9 @@ Runtime note:
   - `wowee_fsr3_vk_wrapper` (output in `build/bin`).
 - Wrapper backend runtime override:
   - `WOWEE_FSR3_WRAPPER_BACKEND_LIB=/absolute/path/to/libffx_fsr3_vk.so` (or `.dll` / `.dylib`).
+- Wrapper backend mode selection:
+  - `WOWEE_FSR3_WRAPPER_BACKEND=vulkan_runtime`
+  - `WOWEE_FSR3_WRAPPER_BACKEND=dx12_bridge`
 - Path B wrapper ABI contract is declared in:
   - `include/rendering/amd_fsr3_wrapper_abi.h`
 - Required wrapper exports:

src/rendering/amd_fsr3_wrapper_impl.cpp

@@ -7,6 +7,7 @@
 
 #include <algorithm>
 #include <array>
+#include <cctype>
 #include <cstdint>
 #include <cstdlib>
 #include <cstring>
@@ -36,6 +37,32 @@ void writeError(char* outErrorText, uint32_t outErrorTextCapacity, const char* m
 }
 
 #if WOWEE_HAS_AMD_FSR3_FRAMEGEN
+enum class WrapperBackend {
+    VulkanRuntime,
+    Dx12Bridge
+};
+
+WrapperBackend selectBackend() {
+    if (const char* envBackend = std::getenv("WOWEE_FSR3_WRAPPER_BACKEND")) {
+        if (envBackend && *envBackend) {
+            std::string mode(envBackend);
+            std::transform(mode.begin(), mode.end(), mode.begin(),
+                           [](unsigned char c) { return static_cast<char>(std::tolower(c)); });
+            if (mode == "dx12" || mode == "dx12_bridge" || mode == "d3d12") {
+                return WrapperBackend::Dx12Bridge;
+            }
+            if (mode == "vulkan" || mode == "vk" || mode == "vulkan_runtime") {
+                return WrapperBackend::VulkanRuntime;
+            }
+        }
+    }
+#if defined(_WIN32)
+    return WrapperBackend::Dx12Bridge;
+#else
+    return WrapperBackend::VulkanRuntime;
+#endif
+}
+
 FfxErrorCode vkSwapchainConfigureNoop(const FfxFrameGenerationConfig*) {
     return FFX_OK;
 }
@@ -207,7 +234,7 @@ WOWEE_FSR3_WRAPPER_EXPORT uint32_t wowee_fsr3_wrapper_get_abi_version(void) {
 }
 
 WOWEE_FSR3_WRAPPER_EXPORT const char* wowee_fsr3_wrapper_get_name(void) {
-    return "WoWee FSR3 DX12/VK Wrapper";
+    return "WoWee FSR3 Wrapper";
 }
 
 WOWEE_FSR3_WRAPPER_EXPORT int32_t wowee_fsr3_wrapper_initialize(const WoweeFsr3WrapperInitDesc* initDesc,
@@ -237,6 +264,18 @@ WOWEE_FSR3_WRAPPER_EXPORT int32_t wowee_fsr3_wrapper_initialize(const WoweeFsr3W
         return -1;
     }
 
+    if (selectBackend() == WrapperBackend::Dx12Bridge) {
+#if !defined(_WIN32)
+        writeError(outErrorText, outErrorTextCapacity,
+                   "dx12_bridge backend is Windows-only in current wrapper build");
+        return -1;
+#else
+        writeError(outErrorText, outErrorTextCapacity,
+                   "dx12_bridge backend selected but Vulkan<->DX12 interop dispatch is not implemented yet");
+        return -1;
+#endif
+    }
+
     std::vector<std::string> candidates;
     if (const char* backendEnv = std::getenv("WOWEE_FSR3_WRAPPER_BACKEND_LIB")) {
         if (*backendEnv) candidates.emplace_back(backendEnv);