video_core: temporal upscale stand-in for Fortune's Weave's DLSS

The one-frame blit left 3D edges aliased and shaking: the game jitters
its camera every frame for DLSS to accumulate. Fire Emblem: Fortune's
Weave's first DLSS pass (also rejected) has the motion vectors
(cbuf0+0x290, R16G16) and the frame's jitter (+0x1b0/+0x1b4, in input
pixels). Kepler compute keeps them, and the stand-in for the last
network pass now draws temporal_upscale.frag: input samples placed where
the jitter put them and weighted by distance, blended with the previous
result reprojected along the motion vectors (Catmull-Rom) and clipped to
the 3x3 neighbourhood in YCoCg. The history is copied from the result
right after drawing it, so post-processing the game later applies to its
output does not feed back. EDEN_NX2_TEMPORAL_UPSCALE=0 restores the blit.

Assisted-by: Claude Opus 5.5 (debugging, implementation and drafting)
Signed-off-by: Duck912 <350528965+Duck912@users.noreply.github.com>

2 files changed, 54 insertions, 1 deletions

diff --git a/src/video_core/engines/kepler_compute.cpp b/src/video_core/engines/kepler_compute.cpp
index 233304d273..b8a6567907 100644
--- a/src/video_core/engines/kepler_compute.cpp
+++ b/src/video_core/engines/kepler_compute.cpp
@@ -6,6 +6,7 @@
 
 #include <algorithm>
 #include <atomic>
+#include <bit>
 #include <bitset>
 #include <cstdlib>
 #include <fstream>
@@ -557,6 +558,7 @@ bool KeplerCompute::DispatchNativeCompute(const NativeQmdScheduler::Descriptor&
             // The console runs this on tensor cores; stand in with a plain upscale of its input.
             return UpscaleInsteadOfNativeProgram();
         }
+        RememberDlssMotionVectors();
         return false;
     }
     return true;
@@ -588,6 +590,30 @@ void KeplerCompute::DescribeNativeResources(const NativeQmdScheduler::Descriptor
 
 std::atomic<u32> g_nx2_trace_draws_after_upscale{};
 
+// Fire Emblem: Fortune's Weave's first DLSS pass (rejected, before the network) has the input colour
+// at cbuf0+0x278, its motion vectors (R16G16 float, the input's size) at +0x290 and this frame's
+// camera jitter (x, y; input pixels, Halton bases 2 and 3 less 0.5) at +0x1b0.
+void KeplerCompute::RememberDlssMotionVectors() {
+    const auto& cbuf = launch_description.const_buffer_config[0];
+    if (cbuf.size.Value() < 0x294) return;
+    const GPUVAddr cbuf_address = (GPUVAddr{cbuf.address_high} << 32) | cbuf.address_low;
+    const auto image = [&](u32 offset) -> std::optional<Texture::TICEntry> {
+        const u32 tic_index = memory_manager.Read<u32>(cbuf_address + offset) & 0xfffff;
+        if (tic_index > regs.tic.limit) return std::nullopt;
+        return GetTICEntry(tic_index);
+    };
+    const auto color = image(0x278), motion = image(0x290);
+    if (!color || !motion || color->format != Texture::TextureFormat::B10G11R11 ||
+        motion->format != Texture::TextureFormat::R16G16 || motion->Address() == 0 ||
+        motion->Width() != color->Width() || motion->Height() != color->Height() ||
+        !motion->IsBlockLinear())
+        return;
+    dlss_motion_vectors = *motion;
+    dlss_motion_color = color->Address();
+    dlss_jitter = {std::bit_cast<f32>(memory_manager.Read<u32>(cbuf_address + 0x1b0)),
+                   std::bit_cast<f32>(memory_manager.Read<u32>(cbuf_address + 0x1b4))};
+}
+
 // Title 4's upscaler reads the tonemapped frame through the texture handle at cbuf0+0x90 and
 // writes the output resolution image through the surface handle at cbuf0+0xa0 (from its
 // TLD/SUST operands). Fire Emblem: Fortune's Weave's DLSS network ends with a pass that reads the
@@ -609,10 +635,12 @@ bool KeplerCompute::UpscaleInsteadOfNativeProgram() {
                output->IsBlockLinear();
     };
     auto input = image(0x90), output = image(0xa0);
+    bool fortunes_weave = false;
     if (!usable(input, output)) {
         input = image(0x328);
         output = image(0x348);
         if (!usable(input, output)) return false;
+        fortunes_weave = true;
     }
     using RTFormat = Tegra::RenderTargetFormat;
     RTFormat format{};
@@ -709,7 +737,24 @@ bool KeplerCompute::UpscaleInsteadOfNativeProgram() {
             source.format = static_cast<RTFormat>(std::strtoul(value, nullptr, 16));
         }
     }
-    const bool done = rasterizer->AccelerateSurfaceCopy(source, surface(*output), config);
+    // Fortune's Weave: a temporal upscale along its motion vectors that undoes this frame's camera
+    // jitter (both from the frame's first DLSS pass) and accumulates the frames as DLSS would.
+    // EDEN_NX2_TEMPORAL_UPSCALE=0 blits instead.
+    const auto upscale_temporally = [&] {
+        static const bool enabled = [] {
+            const char* value = std::getenv("EDEN_NX2_TEMPORAL_UPSCALE");
+            return value == nullptr || std::string_view{value} != "0";
+        }();
+        if (!fortunes_weave || !enabled || !dlss_motion_vectors ||
+            dlss_motion_color != input->Address())
+            return false;
+        Fermi2D::Surface motion = surface(*dlss_motion_vectors);
+        motion.format = RTFormat::R16G16_FLOAT;
+        return rasterizer->AccelerateTemporalUpscale(source, surface(*output), motion, dlss_jitter,
+                                                     {1.0f, 1.0f});
+    };
+    const bool done = upscale_temporally() ||
+                      rasterizer->AccelerateSurfaceCopy(source, surface(*output), config);
     if (static u32 checked{}; checked++ == sample_at) {
         const u64 size = u64{output->Width()} * output->Height() * 4;
         if (const auto device = memory_manager.GpuToCpuAddress(output->Address())) {
diff --git a/src/video_core/engines/kepler_compute.h b/src/video_core/engines/kepler_compute.h
index b525636dde..b5aee3706a 100644
--- a/src/video_core/engines/kepler_compute.h
+++ b/src/video_core/engines/kepler_compute.h
@@ -266,7 +266,15 @@ private:
     bool DispatchNativeCompute(const NativeQmdScheduler::Descriptor& descriptor);
     void ProcessNativeReportSemaphore(u32 argument);
     void DescribeNativeResources(const NativeQmdScheduler::Descriptor& qmd);
+    void RememberDlssMotionVectors();
     bool UpscaleInsteadOfNativeProgram();
+
+    /// Motion vectors of Fire Emblem: Fortune's Weave's DLSS evaluation, from its first pass (run
+    /// earlier in the frame than the network pass the stand-in replaces), with the input colour
+    /// image and camera jitter they go with.
+    std::optional<Texture::TICEntry> dlss_motion_vectors;
+    GPUVAddr dlss_motion_color{};
+    std::array<f32, 2> dlss_jitter{};
     bool ProcessNativeMethod(Core::System& system, u32 method, u32 argument, bool is_last_call);
     NativeQmdScheduler native_qmd;
     std::array<u32, 0xc00>* native_data_ram{};