Optimize Screen Space Reflections tracing with Hierarchical Z-Buffer

Improve SSR resolve filter quality and adjust scalability.

Content/Editor/MaterialTemplates/Features/ForwardShading.hlsl

@@ -116,7 +116,7 @@ void PS_Forward(
 	Texture2D sceneColorTexture = MATERIAL_REFLECTIONS_SSR_COLOR;
 	float2 screenUV = materialInput.SvPosition.xy * ScreenSize.zw;
 	float stepSize = ScreenSize.z; // 1 / screenWidth
-	float maxSamples = 48;
+	float maxSamples = 50;
 	float worldAntiSelfOcclusionBias = 0.1f;
 	float brdfBias = 0.82f;
 	float drawDistance = 5000.0f;

Source/Engine/Graphics/RenderBuffers.cpp

@@ -64,6 +64,7 @@ void RenderBuffers::ReleaseUnusedMemory()
     UPDATE_LAZY_KEEP_RT(TemporalSSR);
     UPDATE_LAZY_KEEP_RT(TemporalAA);
     UPDATE_LAZY_KEEP_RT(HalfResDepth);
+    UPDATE_LAZY_KEEP_RT(HiZ);
     UPDATE_LAZY_KEEP_RT(LuminanceMap);
 #undef UPDATE_LAZY_KEEP_RT
     for (int32 i = CustomBuffers.Count() - 1; i >= 0; i--)
@@ -112,6 +113,42 @@ GPUTexture* RenderBuffers::RequestHalfResDepth(GPUContext* context)
     return HalfResDepth;
 }
 
+GPUTexture* RenderBuffers::RequestHiZ(GPUContext* context, bool fullRes, int32 mipLevels)
+{
+    // Skip if already done in the current frame
+    const auto currentFrame = Engine::FrameCount;
+    if (LastFrameHiZ == currentFrame)
+        return HiZ;
+    LastFrameHiZ = currentFrame;
+
+    // Allocate or resize buffer (with full mip-chain)
+    // TODO: migrate to inverse depth and try using r16 again as default (should have no artifacts anymore)
+    auto format = PLATFORM_ANDROID || PLATFORM_IOS || PLATFORM_SWITCH ? PixelFormat::R16_UInt : PixelFormat::R32_Float;
+    auto width = fullRes ? _width : Math::Max(_width >> 1, 1);
+    auto height = fullRes ? _height : Math::Max(_height >> 1, 1);
+    auto desc = GPUTextureDescription::New2D(width, height, mipLevels, format, GPUTextureFlags::ShaderResource);
+    bool useCompute = false; // TODO: impl Compute Shader for downscaling depth to HiZ with a single dispatch (eg. FidelityFX Single Pass Downsampler)
+    if (useCompute)
+        desc.Flags |= GPUTextureFlags::UnorderedAccess;
+    else
+        desc.Flags |= GPUTextureFlags::RenderTarget | GPUTextureFlags::PerMipViews;
+    if (HiZ && HiZ->GetDescription() != desc)
+    {
+        RenderTargetPool::Release(HiZ);
+        HiZ = nullptr;
+    }
+    if (HiZ == nullptr)
+    {
+        HiZ = RenderTargetPool::Get(desc);
+        RENDER_TARGET_POOL_SET_NAME(HiZ, "HiZ");
+    }
+
+    // Downscale
+    MultiScaler::Instance()->BuildHiZ(context, DepthBuffer, HiZ);
+
+    return HiZ;
+}
+
 PixelFormat RenderBuffers::GetOutputFormat() const
 {
     auto colorFormat = GraphicsSettings::Get()->RenderColorFormat;
@@ -244,6 +281,7 @@ void RenderBuffers::Release()
     UPDATE_LAZY_KEEP_RT(TemporalSSR);
     UPDATE_LAZY_KEEP_RT(TemporalAA);
     UPDATE_LAZY_KEEP_RT(HalfResDepth);
+    UPDATE_LAZY_KEEP_RT(HiZ);
     UPDATE_LAZY_KEEP_RT(LuminanceMap);
 #undef UPDATE_LAZY_KEEP_RT
     CustomBuffers.ClearDelete();

Source/Engine/Graphics/RenderBuffers.h

@@ -43,6 +43,12 @@ API_CLASS() class FLAXENGINE_API RenderBuffers : public ScriptingObject
         String ToString() const override;
     };
 
+private:
+    GPUTexture* HalfResDepth = nullptr;
+    GPUTexture* HiZ = nullptr;
+    uint64 LastFrameHalfResDepth = 0;
+    uint64 LastFrameHiZ = 0;
+
 protected:
     int32 _width = 0;
     int32 _height = 0;
@@ -85,11 +91,6 @@ public:
         float MaxDistance;
     } VolumetricFogData;
 
-    // Helper buffer with half-resolution depth buffer shared by effects (eg. SSR, Motion Blur). Valid only during frame rendering and on request (see RequestHalfResDepth).
-    // Should be released if not used for a few frames.
-    GPUTexture* HalfResDepth = nullptr;
-    uint64 LastFrameHalfResDepth = 0;
-
     // Helper target for the temporal SSR.
     // Should be released if not used for a few frames.
     GPUTexture* TemporalSSR = nullptr;
@@ -122,6 +123,15 @@ public:
     /// <returns>The half-res depth buffer.</returns>
     GPUTexture* RequestHalfResDepth(GPUContext* context);
 
+    /// <summary>
+    /// Requests the Hierarchical Z-Buffer (closest) to be prepared for the current frame.
+    /// </summary>
+    /// <param name="context">The context.</param>
+    /// <param name="fullRes">Generates the full-resolution buffer, otherwise HiZ starts at half-res of the original Depth Buffer.</param>
+    /// <param name="mipLevels">Maximum amount of mip levels to generate. Value 0 generates a full mip chain down to 1x1.</param>
+    /// <returns>The HiZ depth buffer.</returns>
+    GPUTexture* RequestHiZ(GPUContext* context, bool fullRes = false, int32 mipLevels = 0);
+
 public:
     /// <summary>
     /// Gets the buffers width (in pixels).

Source/Engine/Renderer/ReflectionsPass.cpp

@@ -411,6 +411,7 @@ void ReflectionsPass::Render(RenderContext& renderContext, GPUTextureView* light
     else
     {
         // Combine reflections and light buffer (additive mode)
+        PROFILE_GPU("Combine");
         if (_depthBounds)
         {
             context->SetRenderTarget(depthBufferRTV, lightBuffer);

Source/Engine/Renderer/ScreenSpaceReflectionsPass.cpp

@@ -22,19 +22,21 @@
 #define TEXTURE1 5
 #define TEXTURE2 6
 
+#define SSR_USE_HZB 1
+
 GPU_CB_STRUCT(Data {
     ShaderGBufferData GBuffer;
     float MaxColorMiplevel;
     float TraceSizeMax;
     float MaxTraceSamples;
     float RoughnessFade;
-    Float2 SSRtexelSize;
+    Float2 SSRTexelSize;
     float TemporalTime;
     float BRDFBias;
     float WorldAntiSelfOcclusionBias;
     float EdgeFadeFactor;
     float TemporalResponse;
-    float Dummy0;
+    uint32 DepthMips;
     float RayTraceStep;
     float TemporalEffect;
     float Intensity;
@@ -157,10 +159,10 @@ GPUTexture* ScreenSpaceReflectionsPass::Render(RenderContext& renderContext, GPU
     const auto colorBufferMips = MipLevelsCount(colorBufferWidth, colorBufferHeight);
 
     // Prepare buffers
-    auto tempDesc = GPUTextureDescription::New2D(colorBufferWidth, colorBufferHeight, 0, PixelFormat::R11G11B10_Float, GPUTextureFlags::ShaderResource | GPUTextureFlags::RenderTarget | GPUTextureFlags::PerMipViews);
     GPUTexture* colorBuffer0, *colorBuffer1;
     if (settings.UseColorBufferMips)
     {
+        auto tempDesc = GPUTextureDescription::New2D(colorBufferWidth, colorBufferHeight, 0, PixelFormat::R11G11B10_Float, GPUTextureFlags::ShaderResource | GPUTextureFlags::RenderTarget | GPUTextureFlags::PerMipViews);
         colorBuffer0 = RenderTargetPool::Get(tempDesc);
         RENDER_TARGET_POOL_SET_NAME(colorBuffer0, "SSR.ColorBuffer0");
         // TODO: maybe allocate colorBuffer1 smaller because mip0 is not used (the same as PostProcessingPass for Bloom), keep in sync to use the same buffer in frame
@@ -170,27 +172,33 @@ GPUTexture* ScreenSpaceReflectionsPass::Render(RenderContext& renderContext, GPU
     else
     {
         // Single mip
-        tempDesc.MipLevels = 1;
-        tempDesc.Flags &= ~GPUTextureFlags::PerMipViews;
+        auto tempDesc = GPUTextureDescription::New2D(colorBufferWidth, colorBufferHeight, 1, PixelFormat::R11G11B10_Float);
         colorBuffer0 = RenderTargetPool::Get(tempDesc);
         colorBuffer1 = nullptr;
     }
-    tempDesc = GPUTextureDescription::New2D(traceWidth, traceHeight, PixelFormat::R16G16B16A16_Float);
-    auto traceBuffer = RenderTargetPool::Get(tempDesc);
-    RENDER_TARGET_POOL_SET_NAME(traceBuffer, "SSR.TraceBuffer");
-    tempDesc = GPUTextureDescription::New2D(resolveWidth, resolveHeight, PixelFormat::R16G16B16A16_Float);
-    auto resolveBuffer = RenderTargetPool::Get(tempDesc);
-    RENDER_TARGET_POOL_SET_NAME(resolveBuffer, "SSR.ResolveBuffer");
+    GPUTexture* traceBuffer, *resolveBuffer;
+    {
+        auto tempDesc = GPUTextureDescription::New2D(traceWidth, traceHeight, PixelFormat::R16G16B16A16_Float);
+        traceBuffer = RenderTargetPool::Get(tempDesc);
+        RENDER_TARGET_POOL_SET_NAME(traceBuffer, "SSR.TraceBuffer");
+        tempDesc.Width = resolveWidth;
+        tempDesc.Height = resolveHeight;
+        resolveBuffer = RenderTargetPool::Get(tempDesc);
+        RENDER_TARGET_POOL_SET_NAME(resolveBuffer, "SSR.ResolveBuffer");
+    }
 
     // Pick effect settings
     int32 maxTraceSamples = 60;
+    int32 resolveSamples = settings.ResolveSamples;
     switch (Graphics::SSRQuality)
     {
     case Quality::Low:
-        maxTraceSamples = 20;
+        maxTraceSamples = 40;
+        resolveSamples = Math::Min(resolveSamples, 2);
         break;
     case Quality::Medium:
         maxTraceSamples = 55;
+        resolveSamples = Math::Min(resolveSamples, 4);
         break;
     case Quality::High:
         maxTraceSamples = 70;
@@ -199,7 +207,6 @@ GPUTexture* ScreenSpaceReflectionsPass::Render(RenderContext& renderContext, GPU
         maxTraceSamples = 120;
         break;
     }
-    const int32 resolveSamples = settings.ResolveSamples;
     int32 resolvePassIndex = 0;
     if (resolveSamples >= 8)
         resolvePassIndex = 3;
@@ -214,12 +221,12 @@ GPUTexture* ScreenSpaceReflectionsPass::Render(RenderContext& renderContext, GPU
     data.RoughnessFade = Math::Saturate(settings.RoughnessThreshold);
     data.MaxTraceSamples = static_cast<float>(maxTraceSamples);
     data.BRDFBias = settings.BRDFBias;
-    data.WorldAntiSelfOcclusionBias = settings.WorldAntiSelfOcclusionBias;
+    data.WorldAntiSelfOcclusionBias = settings.WorldAntiSelfOcclusionBias * (int32)settings.DepthResolution;
     data.EdgeFadeFactor = settings.EdgeFadeFactor;
-    data.SSRtexelSize = Float2(1.0f / (float)traceWidth, 1.0f / (float)traceHeight);
+    data.SSRTexelSize = Float2(1.0f / (float)traceWidth, 1.0f / (float)traceHeight);
     data.TraceSizeMax = (float)Math::Max(traceWidth, traceHeight);
-    data.MaxColorMiplevel = settings.UseColorBufferMips ? (float)colorBufferMips - 2.0f : 0.0f;
-    data.RayTraceStep = static_cast<float>(settings.DepthResolution) / (float)width;
+    data.MaxColorMiplevel = settings.UseColorBufferMips ? (float)(colorBufferMips - 2) : 0.0f;
+    data.RayTraceStep = (float)settings.DepthResolution / (float)width;
     data.Intensity = settings.Intensity;
     data.FadeOutDistance = Math::Max(settings.FadeOutDistance, 100.0f);
     data.TemporalResponse = settings.TemporalResponse;
@@ -245,8 +252,16 @@ GPUTexture* ScreenSpaceReflectionsPass::Render(RenderContext& renderContext, GPU
         }
     }
 
-    // Check if resize depth
+    // Prepare depth buffer
+#if SSR_USE_HZB
+    int32 hzbMips = settings.DepthResolution == ResolutionMode::Full ? 5 : 4; // Using lower mips in tracing introduces blocky artifacts
+    bool hzbFullRes = settings.DepthResolution == ResolutionMode::Full;
+    GPUTexture* depthBufferTrace = buffers->RequestHiZ(context, hzbFullRes, hzbMips);
+    data.DepthMips = hzbMips - 1; // Offset to improve SSR range
+#else
     GPUTexture* depthBufferTrace = settings.DepthResolution == ResolutionMode::Half ? buffers->RequestHalfResDepth(context) : buffers->DepthBuffer;
+    data.DepthMips = 1;
+#endif
 
     // Prepare constants
     context->UpdateCB(cb, &data);
@@ -259,16 +274,19 @@ GPUTexture* ScreenSpaceReflectionsPass::Render(RenderContext& renderContext, GPU
     context->BindSR(3, depthBufferTrace);
 
     // Combine pass
-    context->BindSR(TEXTURE0, lightBuffer);
-    context->BindSR(TEXTURE1, reflectionsRT);
-    context->BindSR(TEXTURE2, _preIntegratedGF->GetTexture());
-    context->SetViewportAndScissors((float)colorBufferWidth, (float)colorBufferHeight);
-    context->SetRenderTarget(colorBuffer0->View(0));
-    context->SetState(_psCombinePass);
-    context->DrawFullscreenTriangle();
-    context->UnBindSR(TEXTURE1);
-    context->UnBindSR(TEXTURE2);
-    context->ResetRenderTarget();
+    {
+        PROFILE_GPU("Combine");
+        context->BindSR(TEXTURE0, lightBuffer);
+        context->BindSR(TEXTURE1, reflectionsRT);
+        context->BindSR(TEXTURE2, _preIntegratedGF->GetTexture());
+        context->SetViewportAndScissors((float)colorBufferWidth, (float)colorBufferHeight);
+        context->SetRenderTarget(colorBuffer0->View(0));
+        context->SetState(_psCombinePass);
+        context->DrawFullscreenTriangle();
+        context->UnBindSR(TEXTURE1);
+        context->UnBindSR(TEXTURE2);
+        context->ResetRenderTarget();
+    }
 
     // Blur Pass
     if (settings.UseColorBufferMips)
@@ -298,37 +316,44 @@ GPUTexture* ScreenSpaceReflectionsPass::Render(RenderContext& renderContext, GPU
     RenderTargetPool::Release(colorBuffer1);
 
     // Ray Trace Pass
-    context->SetViewportAndScissors((float)traceWidth, (float)traceHeight);
-    context->SetRenderTarget(*traceBuffer);
-    context->BindSR(TEXTURE0, colorBuffer0->View());
-    if (useGlobalSurfaceAtlas)
     {
-        context->BindSR(7, bindingDataSDF.Texture ? bindingDataSDF.Texture->ViewVolume() : nullptr);
-        context->BindSR(8, bindingDataSDF.TextureMip ? bindingDataSDF.TextureMip->ViewVolume() : nullptr);
-        context->BindSR(9, bindingDataSurfaceAtlas.Chunks ? bindingDataSurfaceAtlas.Chunks->View() : nullptr);
-        context->BindSR(10, bindingDataSurfaceAtlas.CulledObjects ? bindingDataSurfaceAtlas.CulledObjects->View() : nullptr);
-        context->BindSR(11, bindingDataSurfaceAtlas.Objects ? bindingDataSurfaceAtlas.Objects->View() : nullptr);
-        context->BindSR(12, bindingDataSurfaceAtlas.AtlasDepth->View());
-        context->BindSR(13, bindingDataSurfaceAtlas.AtlasLighting->View());
+        PROFILE_GPU("RayTrace");
+        context->SetViewportAndScissors((float)traceWidth, (float)traceHeight);
+        context->SetRenderTarget(*traceBuffer);
+        context->BindSR(TEXTURE0, colorBuffer0->View());
+        if (useGlobalSurfaceAtlas)
+        {
+            context->BindSR(7, bindingDataSDF.Texture ? bindingDataSDF.Texture->ViewVolume() : nullptr);
+            context->BindSR(8, bindingDataSDF.TextureMip ? bindingDataSDF.TextureMip->ViewVolume() : nullptr);
+            context->BindSR(9, bindingDataSurfaceAtlas.Chunks ? bindingDataSurfaceAtlas.Chunks->View() : nullptr);
+            context->BindSR(10, bindingDataSurfaceAtlas.CulledObjects ? bindingDataSurfaceAtlas.CulledObjects->View() : nullptr);
+            context->BindSR(11, bindingDataSurfaceAtlas.Objects ? bindingDataSurfaceAtlas.Objects->View() : nullptr);
+            context->BindSR(12, bindingDataSurfaceAtlas.AtlasDepth->View());
+            context->BindSR(13, bindingDataSurfaceAtlas.AtlasLighting->View());
+        }
+        context->SetState(_psRayTracePass.Get(useGlobalSurfaceAtlas ? 1 : 0));
+        context->DrawFullscreenTriangle();
+        context->ResetRenderTarget();
+        RenderTargetPool::Release(colorBuffer0);
     }
-    context->SetState(_psRayTracePass.Get(useGlobalSurfaceAtlas ? 1 : 0));
-    context->DrawFullscreenTriangle();
-    context->ResetRenderTarget();
-    RenderTargetPool::Release(colorBuffer0);
 
     // Resolve Pass
-    context->SetViewportAndScissors((float)resolveWidth, (float)resolveHeight);
-    context->SetRenderTarget(resolveBuffer->View());
-    context->BindSR(TEXTURE0, traceBuffer->View());
-    context->SetState(_psResolvePass.Get(resolvePassIndex));
-    context->DrawFullscreenTriangle();
-    context->ResetRenderTarget();
-    RenderTargetPool::Release(traceBuffer);
+    {
+        PROFILE_GPU("Resolve");
+        context->SetViewportAndScissors((float)resolveWidth, (float)resolveHeight);
+        context->SetRenderTarget(resolveBuffer->View());
+        context->BindSR(TEXTURE0, traceBuffer->View());
+        context->SetState(_psResolvePass.Get(resolvePassIndex));
+        context->DrawFullscreenTriangle();
+        context->ResetRenderTarget();
+        RenderTargetPool::Release(traceBuffer);
+    }
 
     // Temporal Pass
     GPUTexture* reflectionsBuffer = resolveBuffer;
     if (useTemporal)
     {
+        PROFILE_GPU("Temporal");
         buffers->LastFrameTemporalSSR = Engine::FrameCount;
         bool resetHistory = false;
         if (!buffers->TemporalSSR || buffers->TemporalSSR->Width() != resolveWidth || buffers->TemporalSSR->Height() != resolveHeight)
@@ -336,7 +361,7 @@ GPUTexture* ScreenSpaceReflectionsPass::Render(RenderContext& renderContext, GPU
             resetHistory = true;
             if (buffers->TemporalSSR)
                 RenderTargetPool::Release(buffers->TemporalSSR);
-            tempDesc = GPUTextureDescription::New2D(resolveWidth, resolveHeight, PixelFormat::R16G16B16A16_Float);
+            auto tempDesc = GPUTextureDescription::New2D(resolveWidth, resolveHeight, PixelFormat::R16G16B16A16_Float);
             buffers->TemporalSSR = RenderTargetPool::Get(tempDesc);
             RENDER_TARGET_POOL_SET_NAME(buffers->TemporalSSR, "SSR.TemporalSSR");
         }

Source/Engine/Renderer/Utils/MultiScaler.cpp

@@ -2,8 +2,8 @@
 
 #include "MultiScaler.h"
 #include "Engine/Graphics/Textures/GPUTexture.h"
-#include "Engine/Content/Content.h"
 #include "Engine/Graphics/GPUContext.h"
+#include "Engine/Content/Content.h"
 
 GPU_CB_STRUCT(Data {
     Float2 TexelSize;
@@ -18,10 +18,10 @@ String MultiScaler::ToString() const
 bool MultiScaler::Init()
 {
     // Create pipeline states
-    _psHalfDepth = GPUDevice::Instance->CreatePipelineState();
     _psBlur5.CreatePipelineStates();
     _psBlur9.CreatePipelineStates();
     _psBlur13.CreatePipelineStates();
+    _psHalfDepth.CreatePipelineStates();
     _psUpscale = GPUDevice::Instance->CreatePipelineState();
 
     // Load asset
@@ -66,13 +66,20 @@ bool MultiScaler::setupResources()
         if (_psUpscale->Init(psDesc))
             return true;
     }
-    if (!_psHalfDepth->IsValid())
+    if (!_psHalfDepth.IsValid())
     {
-        psDesc.PS = shader->GetPS("PS_HalfDepth");
+        psDesc.PS = shader->GetPS("PS_HalfDepth", 0);
+        if (_psHalfDepth[0]->Init(psDesc))
+            return true;
+        psDesc.PS = shader->GetPS("PS_HalfDepth", 2);
+        psDesc.BlendMode.RenderTargetWriteMask = BlendingMode::ColorWrite::Red;
+        if (_psHalfDepth[2]->Init(psDesc))
+            return true;
+        psDesc.PS = shader->GetPS("PS_HalfDepth", 1);
         psDesc.DepthWriteEnable = true;
         psDesc.DepthEnable = true;
         psDesc.DepthFunc = ComparisonFunc::Always;
-        if (_psHalfDepth->Init(psDesc))
+        if (_psHalfDepth[1]->Init(psDesc))
             return true;
     }
 
@@ -85,15 +92,15 @@ void MultiScaler::Dispose()
     RendererPass::Dispose();
 
     // Cleanup
-    SAFE_DELETE_GPU_RESOURCE(_psHalfDepth);
     SAFE_DELETE_GPU_RESOURCE(_psUpscale);
     _psBlur5.Delete();
     _psBlur9.Delete();
     _psBlur13.Delete();
+    _psHalfDepth.Delete();
     _shader = nullptr;
 }
 
-void MultiScaler::Filter(const FilterMode mode, GPUContext* context, const int32 width, const int32 height, GPUTextureView* src, GPUTextureView* dst, GPUTextureView* tmp)
+void MultiScaler::Filter(FilterMode mode, GPUContext* context, int32 width, int32 height, GPUTextureView* src, GPUTextureView* dst, GPUTextureView* tmp)
 {
     PROFILE_GPU_CPU("MultiScaler Filter");
 
@@ -152,18 +159,14 @@ void MultiScaler::Filter(const FilterMode mode, GPUContext* context, const int32
     context->ResetRenderTarget();
 }
 
-void MultiScaler::Filter(const FilterMode mode, GPUContext* context, const int32 width, const int32 height, GPUTextureView* srcDst, GPUTextureView* tmp)
+void MultiScaler::Filter(FilterMode mode, GPUContext* context, int32 width, int32 height, GPUTextureView* srcDst, GPUTextureView* tmp)
 {
     PROFILE_GPU_CPU("MultiScaler Filter");
 
     context->SetViewportAndScissors((float)width, (float)height);
 
-    // Check if has missing resources
     if (checkIfSkipPass())
-    {
-        // Skip
         return;
-    }
 
     // Select filter
     GPUPipelineStatePermutationsPs<2>* ps;
@@ -211,11 +214,8 @@ void MultiScaler::Filter(const FilterMode mode, GPUContext* context, const int32
 void MultiScaler::DownscaleDepth(GPUContext* context, int32 dstWidth, int32 dstHeight, GPUTexture* src, GPUTextureView* dst)
 {
     PROFILE_GPU_CPU("Downscale Depth");
-
-    // Check if has missing resources
     if (checkIfSkipPass())
     {
-        // Clear the output
         context->ClearDepth(dst);
         return;
     }
@@ -224,6 +224,7 @@ void MultiScaler::DownscaleDepth(GPUContext* context, int32 dstWidth, int32 dstH
     Data data;
     data.TexelSize.X = 1.0f / (float)src->Width();
     data.TexelSize.Y = 1.0f / (float)src->Height();
+    bool outputDepth = ((GPUTexture*)dst->GetParent())->IsDepthStencil();
     auto cb = _shader->GetShader()->GetCB(0);
     context->UpdateCB(cb, &data);
     context->BindCB(0, cb);
@@ -232,7 +233,7 @@ void MultiScaler::DownscaleDepth(GPUContext* context, int32 dstWidth, int32 dstH
     context->SetViewportAndScissors((float)dstWidth, (float)dstHeight);
     context->SetRenderTarget(dst, (GPUTextureView*)nullptr);
     context->BindSR(0, src);
-    context->SetState(_psHalfDepth);
+    context->SetState(_psHalfDepth[outputDepth ? 1 : 0]);
     context->DrawFullscreenTriangle();
 
     // Cleanup
@@ -240,6 +241,49 @@ void MultiScaler::DownscaleDepth(GPUContext* context, int32 dstWidth, int32 dstH
     context->UnBindCB(0);
 }
 
+void MultiScaler::BuildHiZ(GPUContext* context, GPUTexture* srcDepth, GPUTexture* dstHiZ)
+{
+    PROFILE_GPU_CPU("Build HiZ");
+
+    int32 dstWidth = dstHiZ->Width();
+    int32 dstHeight = dstHiZ->Height();
+
+    // Copy mip0
+    if (srcDepth->Size() == dstHiZ->Size() && srcDepth->Format() == dstHiZ->Format())
+    {
+        context->CopySubresource(dstHiZ, 0, srcDepth, 0);
+    }
+    else if (srcDepth->Size() == dstHiZ->Size())
+    {
+        context->Draw(dstHiZ, srcDepth);
+    }
+    else
+    {
+        context->SetViewportAndScissors((float)dstWidth, (float)dstHeight);
+        context->SetRenderTarget(dstHiZ->View());
+        context->BindSR(0, srcDepth);
+        context->SetState(_psHalfDepth[2]);
+        context->DrawFullscreenTriangle();
+    }
+
+    // Build mip chain
+    for (int32 mip = 1; mip < dstHiZ->MipLevels(); mip++)
+    {
+        const int32 mipWidth = Math::Max(dstWidth >> mip, 1);
+        const int32 mipHeight = Math::Max(dstHeight >> mip, 1);
+        context->ResetRenderTarget();
+
+        context->SetViewportAndScissors((float)mipWidth, (float)mipHeight);
+        context->SetRenderTarget(dstHiZ->View(0, mip));
+        context->BindSR(0, dstHiZ->View(0, mip - 1));
+        context->SetState(_psHalfDepth[2]);
+        context->DrawFullscreenTriangle();
+    }
+
+    context->ResetRenderTarget();
+    context->UnBindCB(0);
+}
+
 void MultiScaler::Upscale(GPUContext* context, const Viewport& viewport, GPUTexture* src, GPUTextureView* dst)
 {
     PROFILE_GPU_CPU("Upscale");

Source/Engine/Renderer/Utils/MultiScaler.h

@@ -12,16 +12,14 @@
 class MultiScaler : public RendererPass<MultiScaler>
 {
 private:
-
     AssetReference<Shader> _shader;
-    GPUPipelineState* _psHalfDepth = nullptr;
     GPUPipelineStatePermutationsPs<2> _psBlur5;
     GPUPipelineStatePermutationsPs<2> _psBlur9;
     GPUPipelineStatePermutationsPs<2> _psBlur13;
+    GPUPipelineStatePermutationsPs<3> _psHalfDepth;
     GPUPipelineState* _psUpscale = nullptr;
 
 public:
-
     /// <summary>
     /// Filter mode
     /// </summary>
@@ -53,7 +51,7 @@ public:
     /// <param name="src">The source texture.</param>
     /// <param name="dst">The destination texture.</param>
     /// <param name="tmp">The temporary texture (should have the same size as destination texture).</param>
-    void Filter(const FilterMode mode, GPUContext* context, const int32 width, const int32 height, GPUTextureView* src, GPUTextureView* dst, GPUTextureView* tmp);
+    void Filter(FilterMode mode, GPUContext* context, int32 width, int32 height, GPUTextureView* src, GPUTextureView* dst, GPUTextureView* tmp);
 
     /// <summary>
     /// Performs texture filtering.
@@ -64,18 +62,26 @@ public:
     /// <param name="height">The output height.</param>
     /// <param name="srcDst">The source and destination texture.</param>
     /// <param name="tmp">The temporary texture (should have the same size as destination texture).</param>
-    void Filter(const FilterMode mode, GPUContext* context, const int32 width, const int32 height, GPUTextureView* srcDst, GPUTextureView* tmp);
+    void Filter(FilterMode mode, GPUContext* context, int32 width, int32 height, GPUTextureView* srcDst, GPUTextureView* tmp);
 
     /// <summary>
-    /// Downscales the depth buffer (to half resolution).
+    /// Downscales the depth buffer (to half resolution). Uses `min` operator (`max` for inverted depth) to output the furthest depths for conservative usage.
     /// </summary>
     /// <param name="context">The context.</param>
     /// <param name="dstWidth">The width of the destination texture (in pixels).</param>
     /// <param name="dstHeight">The height of the destination texture (in pixels).</param>
-    /// <param name="src">The source texture.</param>
-    /// <param name="dst">The destination texture.</param>
+    /// <param name="src">The source texture (has to have ShaderResource flag).</param>
+    /// <param name="dst">The destination texture (has to have DepthStencil or RenderTarget flag).</param>
     void DownscaleDepth(GPUContext* context, int32 dstWidth, int32 dstHeight, GPUTexture* src, GPUTextureView* dst);
 
+    /// <summary>
+    /// Generates the Hierarchical Z-Buffer (HiZ). Uses `min` operator (`max` for inverted depth) to output the furthest depths for conservative usage.
+    /// </summary>
+    /// <param name="context">The context.</param>
+    /// <param name="srcDepth">The source depth buffer texture (has to have ShaderResource flag).</param>
+    /// <param name="dstHiZ">The destination HiZ texture (has to have DepthStencil or RenderTarget flag).</param>
+    void BuildHiZ(GPUContext* context, GPUTexture* srcDepth, GPUTexture* dstHiZ);
+
     /// <summary>
     /// Upscales the texture.
     /// </summary>
@@ -86,7 +92,6 @@ public:
     void Upscale(GPUContext* context, const Viewport& viewport, GPUTexture* src, GPUTextureView* dst);
 
 public:
-
     // [RendererPass]
     String ToString() const override;
     bool Init() override;
@@ -94,17 +99,16 @@ public:
 #if COMPILE_WITH_DEV_ENV
     void OnShaderReloading(Asset* obj)
     {
-        _psHalfDepth->ReleaseGPU();
         _psUpscale->ReleaseGPU();
         _psBlur5.Release();
         _psBlur9.Release();
         _psBlur13.Release();
+        _psHalfDepth.Release();
         invalidateResources();
     }
 #endif
 
 protected:
-
     // [RendererPass]
     bool setupResources() override;
 };

Source/Engine/ShadersCompilation/ShadersCompilation.cpp

@@ -443,6 +443,11 @@ String ShadersCompilation::ResolveShaderPath(StringView path)
             // Hard-coded redirect to platform-specific includes
             result = Globals::StartupFolder / TEXT("Source/Platforms");
         }
+        else if (projectName.StartsWith(StringView(TEXT("FlaxThirdParty"))))
+        {
+            // Hard-coded redirect to third-party-specific includes
+            result = Globals::StartupFolder / TEXT("Source/ThirdParty");
+        }
         else
         {
             HashSet<const ProjectInfo*> projects;

Source/Shaders/MultiScaler.shader

@@ -1,6 +1,7 @@
 // Copyright (c) Wojciech Figat. All rights reserved.
 
 #include "./Flax/Common.hlsl"
+#include "./Flax/Gather.hlsl"
 
 META_CB_BEGIN(0, Data)
 float2 TexelSize;
@@ -14,19 +15,24 @@ Texture2D Input : register(t0);
 
 // Pixel Shader for depth buffer downscale (to half res)
 META_PS(true, FEATURE_LEVEL_ES2)
-float PS_HalfDepth(Quad_VS2PS input) : SV_Depth
-{
-#if CAN_USE_GATHER
-	float4 depths = Input.GatherRed(SamplerPointClamp, input.TexCoord);
+META_PERMUTATION_1(OUTPUT_DEPTH=0)
+META_PERMUTATION_1(OUTPUT_DEPTH=1)
+META_PERMUTATION_1(HZB_CLOSEST=2)
+float PS_HalfDepth(Quad_VS2PS input) 
+#if OUTPUT_DEPTH
+    : SV_Depth
 #else
-	float4 depths;
-	depths.x = Input.SampleLevel(SamplerPointClamp, input.TexCoord + float2(0, 1) * TexelSize, 0).r;
-	depths.y = Input.SampleLevel(SamplerPointClamp, input.TexCoord + float2(1, 1) * TexelSize, 0).r;
-	depths.z = Input.SampleLevel(SamplerPointClamp, input.TexCoord + float2(1, 0) * TexelSize, 0).r;
-	depths.w = Input.SampleLevel(SamplerPointClamp, input.TexCoord + float2(0, 0) * TexelSize, 0).r;
+    : SV_Target0
 #endif
+{
+    // Load 4 depth values (2x2 quad)
+	float4 depths = TextureGatherRed(Input, SamplerPointClamp, input.TexCoord);
 
-	return max(depths.x, max(depths.y, max(depths.z, depths.w))) + 0.0001f;
+#if HZB_CLOSEST
+	return min(depths.x, min(depths.y, min(depths.z, depths.w)));
+#else
+	return max(depths.x, max(depths.y, max(depths.z, depths.w)));
+#endif
 }
 
 // Pixel Shader for 5-tap gaussian blur

Source/Shaders/ReflectionsCommon.hlsl

@@ -6,9 +6,6 @@
 #include "./Flax/GBufferCommon.hlsl"
 #include "./Flax/Quaternion.hlsl"
 
-// Hit depth (view space) threshold to detect if sky was hit (value above it where 1.0f is default)
-#define REFLECTIONS_HIT_THRESHOLD 0.9f
-
 // Packed env probe data
 struct EnvProbeData
 {

Source/Shaders/SSR.hlsl

@@ -5,6 +5,9 @@
 #include "./Flax/Random.hlsl"
 #include "./Flax/MonteCarlo.hlsl"
 #include "./Flax/GBufferCommon.hlsl"
+#if SSR_USE_HZB
+#include "./FlaxThirdParty/FidelityFX/ffx_sssr.h"
+#endif
 
 // 1:-1 to 0:1
 float2 ClipToUv(float2 clipPos)
@@ -44,19 +47,22 @@ float RayAttenBorder(float2 pos, float value)
 // Returns: xy: hitUV, z: hitMask, where hitUV is the result UV of hit pixel, hitMask is the normalized sample weight (0 if no hit).
 float3 ScreenSpaceReflectionDirection(float2 uv, GBufferSample gBuffer, float3 viewPos,  bool temporal = false, float temporalTime = 0.0f, float brdfBias = 0.82f)
 {
-    // Randomize it a little
     float2 jitter = RandN2(uv + temporalTime);
     float2 Xi = jitter;
     Xi.y = lerp(Xi.y, 0.0, brdfBias);
     float3 H = temporal ? TangentToWorld(gBuffer.Normal, ImportanceSampleGGX(Xi, gBuffer.Roughness)) : gBuffer.Normal;
-
     float3 viewWS = normalize(gBuffer.WorldPos - viewPos);
     return reflect(viewWS, H.xyz);
 }
 
 // Screen Space Reflection ray tracing utility.
+// If SSR_USE_HZB is defined, it uses Hierarchical Z-Buffer for tracing against screen (assumes that depthBuffer is a HiZ with full mip-chain).
 // Returns: xy: hitUV, z: hitMask, where hitUV is the result UV of hit pixel, hitMask is the normalized sample weight (0 if no hit).
-float3 TraceScreenSpaceReflection(float2 uv, GBufferSample gBuffer, Texture2D depthBuffer, float3 viewPos, float4x4 viewMatrix, float4x4 viewProjectionMatrix, float stepSize, float maxSamples = 20, bool temporal = false, float temporalTime = 0.0f, float worldAntiSelfOcclusionBias = 0.1f, float brdfBias = 0.82f, float drawDistance = 5000.0f, float roughnessThreshold = 0.4f, float edgeFade = 0.1f)
+float3 TraceScreenSpaceReflection(
+#if SSR_USE_HZB
+    out bool uncertainHit, uint hzbMips,
+#endif
+    float2 uv, GBufferSample gBuffer, Texture2D depthBuffer, float3 viewPos, float4x4 viewMatrix, float4x4 viewProjectionMatrix, float stepSize, float maxSamples = 50, bool temporal = false, float temporalTime = 0.0f, float worldAntiSelfOcclusionBias = 0.1f, float brdfBias = 0.82f, float drawDistance = 5000.0f, float roughnessThreshold = 0.4f, float edgeFade = 0.1f)
 {
 #ifndef SSR_SKIP_INVALID_CHECK
     // Reject invalid pixels
@@ -69,17 +75,19 @@ float3 TraceScreenSpaceReflection(float2 uv, GBufferSample gBuffer, Texture2D de
     float3 reflectVS = normalize(reflect(gBuffer.ViewPos, normalVS));
     if (gBuffer.ViewPos.z < 1.0 && reflectVS.z < 0.4)
         return 0;
-
+        
+    // Calculate ray path in UV space (z is raw depth)
     float3 reflectWS = ScreenSpaceReflectionDirection(uv, gBuffer, viewPos, temporal, temporalTime, brdfBias);
+#if SSR_USE_HZB
+    worldAntiSelfOcclusionBias *= 10.0f; // Higher bias for HZB trace to reduce artifacts
+#endif
     float3 startWS = gBuffer.WorldPos + gBuffer.Normal * worldAntiSelfOcclusionBias;
     float3 startUV = ProjectWorldToUv(startWS, viewProjectionMatrix);
     float3 endUV = ProjectWorldToUv(startWS + reflectWS, viewProjectionMatrix);
-
     float3 rayUV = endUV - startUV;
     float2 rayUVAbs = abs(rayUV.xy);
     rayUV *= stepSize / max(rayUVAbs.x, rayUVAbs.y);
     float3 startUv = startUV + rayUV * 2;
-
     float3 currOffset = startUv;
     float3 rayStep = rayUV * 2;
 
@@ -89,26 +97,30 @@ float3 TraceScreenSpaceReflection(float2 uv, GBufferSample gBuffer, Texture2D de
     float numSamples = min(maxSamples, samplesToEdge.x);
     rayStep *= samplesToEdge.x / numSamples;
 
-    // Calculate depth difference error
-    float depthDiffError = 1.3f * abs(rayStep.z);
-
     // Ray trace
+    float depthDiffError = 1.3f * abs(rayStep.z);
+#if SSR_USE_HZB
+    bool validHit = false;
+    uint2 depthBufferSize;
+    depthBuffer.GetDimensions(depthBufferSize.x, depthBufferSize.y);
+    float3 hit = FFX_SSSR_HierarchicalRaymarch(depthBuffer, hzbMips, depthDiffError, uncertainHit, startUV, rayUV, depthBufferSize, 0, numSamples, validHit);
+    if (!validHit)
+        return 0;
+    currOffset = hit;
+#else
     float currSampleIndex = 0;
-    float currSample, depthDiff;
     LOOP
     while (currSampleIndex < numSamples)
     {
         // Sample depth buffer and calculate depth difference
-        currSample = SAMPLE_RT(depthBuffer, currOffset.xy).r;
-        depthDiff = currOffset.z - currSample;
+        float currSample = SAMPLE_RT(depthBuffer, currOffset.xy).r;
+        float depthDiff = currOffset.z - currSample;
 
         // Check intersection
         if (depthDiff >= 0)
         {
             if (depthDiff < depthDiffError)
-            {
                 break;
-            }
             currOffset -= rayStep;
             rayStep *= 0.5;
         }
@@ -117,25 +129,19 @@ float3 TraceScreenSpaceReflection(float2 uv, GBufferSample gBuffer, Texture2D de
         currOffset += rayStep;
         currSampleIndex++;
     }
-
-    // Check if has valid result after ray tracing
     if (currSampleIndex >= numSamples)
-    {
-        // All samples done but no result
-        return 0;
-    }
-
-    float2 hitUV = currOffset.xy;
+        return 0; // All samples done but no result
+#endif
 
     // Fade rays close to screen edge
     const float fadeStart = 0.9f;
     const float fadeEnd = 1.0f;
     const float fadeDiffRcp = 1.0f / (fadeEnd - fadeStart);
-    float2 boundary = abs(hitUV - float2(0.5f, 0.5f)) * 2.0f;
+    float2 boundary = abs(currOffset.xy - float2(0.5f, 0.5f)) * 2.0f;
     float fadeOnBorder = 1.0f - saturate((boundary.x - fadeStart) * fadeDiffRcp);
     fadeOnBorder *= 1.0f - saturate((boundary.y - fadeStart) * fadeDiffRcp);
     fadeOnBorder = smoothstep(0.0f, 1.0f, fadeOnBorder);
-    fadeOnBorder *= RayAttenBorder(hitUV, edgeFade);
+    fadeOnBorder *= RayAttenBorder(currOffset.xy, edgeFade);
 
     // Fade rays on high roughness
     float roughnessFade = saturate((roughnessThreshold - gBuffer.Roughness) * 20);
@@ -144,5 +150,5 @@ float3 TraceScreenSpaceReflection(float2 uv, GBufferSample gBuffer, Texture2D de
     float distanceFade = saturate((drawDistance - gBuffer.ViewPos.z) / drawDistance);
 
     // Output: xy: hitUV, z: hitMask
-    return float3(hitUV, fadeOnBorder * roughnessFade * distanceFade);
+    return float3(currOffset.xy, fadeOnBorder * roughnessFade * distanceFade);
 }

Source/Shaders/SSR.shader

@@ -1,7 +1,14 @@
 // Copyright (c) Wojciech Figat. All rights reserved.
 
+// Skips additional check in TraceScreenSpaceReflection for material that is already done by PS_RayTracePass
 #define SSR_SKIP_INVALID_CHECK 1
 
+// Uses more-optimized Hierarchical Z-Buffer tracing rather than naive Depth Buffer tracing 
+#define SSR_USE_HZB 1
+
+// Enable/disable luminance filter to reduce reflections highlights
+#define SSR_REDUCE_HIGHLIGHTS 1
+
 #include "./Flax/Common.hlsl"
 #include "./Flax/LightingCommon.hlsl"
 #include "./Flax/ReflectionsCommon.hlsl"
@@ -11,8 +18,7 @@
 #include "./Flax/GlobalSignDistanceField.hlsl"
 #include "./Flax/GI/GlobalSurfaceAtlas.hlsl"
 
-// Enable/disable luminance filter to reduce reflections highlights
-#define SSR_REDUCE_HIGHLIGHTS 1
+#define SSR_USE_SDF (USE_GLOBAL_SURFACE_ATLAS && CAN_USE_GLOBAL_SURFACE_ATLAS)
 
 META_CB_BEGIN(0, Data)
 GBufferData GBuffer;
@@ -20,13 +26,13 @@ float MaxColorMiplevel;
 float TraceSizeMax;
 float MaxTraceSamples;
 float RoughnessFade;
-float2 SSRtexelSize;
+float2 SSRTexelSize;
 float TemporalTime;
 float BRDFBias;
 float WorldAntiSelfOcclusionBias;
 float EdgeFadeFactor;
 float TemporalResponse;
-float Dummy0;
+uint DepthMips;
 float RayTraceStep;
 float TemporalEffect;
 float Intensity;
@@ -104,14 +110,31 @@ float4 PS_RayTracePass(Quad_VS2PS input) : SV_Target0
 	GBufferSample gBuffer = SampleGBuffer(gBufferData, input.TexCoord);
 
     // Reject invalid pixels
+    BRANCH
     if (gBuffer.ShadingModel == SHADING_MODEL_UNLIT || gBuffer.Roughness > RoughnessFade || gBuffer.ViewPos.z > FadeOutDistance)
         return base;
 
 	// Trace depth buffer to find intersection
-	float3 screenHit = TraceScreenSpaceReflection(input.TexCoord, gBuffer, Depth, gBufferData.ViewPos, ViewMatrix, ViewProjectionMatrix, RayTraceStep, MaxTraceSamples, TemporalEffect, TemporalTime, WorldAntiSelfOcclusionBias, BRDFBias, FadeOutDistance, RoughnessFade, EdgeFadeFactor);
-	float4 result = base;
+    bool uncertainHit = false;
+	float3 screenHit = TraceScreenSpaceReflection(
+#if SSR_USE_HZB
+        uncertainHit, DepthMips,
+#endif
+        input.TexCoord, gBuffer, Depth, gBufferData.ViewPos, ViewMatrix, ViewProjectionMatrix, RayTraceStep, MaxTraceSamples, TemporalEffect, TemporalTime, WorldAntiSelfOcclusionBias, BRDFBias, FadeOutDistance, RoughnessFade, EdgeFadeFactor);
+    float4 result = base;
+#if SSR_USE_SDF
+	if (screenHit.z > 0 && !uncertainHit) // Only use certain SSR hits when SDF tracing is enabled
+#else
 	if (screenHit.z > 0)
+#endif
 	{
+        if (uncertainHit)
+        {
+            // Jitter edges of uncertain hits (when ray goes behind the object)
+            screenHit.xy += RandN2(input.TexCoord + TemporalTime) * SSRTexelSize;
+        }
+
+        // Sample color buffer mip that matches roughness of the surface to get blurred reflections
 	    float3 viewVector = normalize(gBufferData.ViewPos - gBuffer.WorldPos);
         float NdotV = saturate(dot(gBuffer.Normal, viewVector));
         float coneTangent = lerp(0.0, gBuffer.Roughness * 5 * (1.0 - BRDFBias), pow(NdotV, 1.5) * sqrt(gBuffer.Roughness));
@@ -119,21 +142,28 @@ float4 PS_RayTracePass(Quad_VS2PS input) : SV_Target0
         float mip = clamp(log2(intersectionCircleRadius * TraceSizeMax), 0.0, MaxColorMiplevel);
         float3 sampleColor = Texture0.SampleLevel(SamplerLinearClamp, screenHit.xy, mip).rgb;
         result = float4(sampleColor, screenHit.z);
-        if (screenHit.z >= REFLECTIONS_HIT_THRESHOLD)
+
+#if SSR_USE_SDF
+        // Skip SDF tracing if SSR hit is very certain
+        BRANCH
+        if (result.a > 0.95f)
             return result;
+#endif
 	}
 
     // Fallback to Global SDF and Global Surface Atlas tracing
-#if USE_GLOBAL_SURFACE_ATLAS && CAN_USE_GLOBAL_SURFACE_ATLAS
+#if SSR_USE_SDF
 	// Calculate reflection direction (the same TraceScreenSpaceReflection)
     float3 reflectWS = ScreenSpaceReflectionDirection(input.TexCoord, gBuffer, gBufferData.ViewPos, TemporalEffect, TemporalTime, BRDFBias);
 
+    // Raytrace Global SDF
     GlobalSDFTrace sdfTrace;
     float maxDistance = GLOBAL_SDF_WORLD_SIZE;
     sdfTrace.Init(gBuffer.WorldPos, reflectWS, 0.0f, maxDistance);
     GlobalSDFHit sdfHit = RayTraceGlobalSDF(GlobalSDF, GlobalSDFTex, GlobalSDFMip, sdfTrace, 2.0f);
     if (sdfHit.IsHit())
     {
+        // Sample Global Surface Atlas
         float3 hitPosition = sdfHit.GetHitPosition(sdfTrace);
         float surfaceThreshold = GetGlobalSurfaceAtlasThreshold(GlobalSDF, sdfHit);
         float4 surfaceAtlas = SampleGlobalSurfaceAtlas(GlobalSurfaceAtlas, GlobalSurfaceAtlasChunks, RWGlobalSurfaceAtlasCulledObjects, GlobalSurfaceAtlasObjects, GlobalSurfaceAtlasDepth, GlobalSurfaceAtlasTex, hitPosition, -reflectWS, surfaceThreshold);
@@ -159,28 +189,27 @@ float4 PS_ResolvePass(Quad_VS2PS input) : SV_Target0
 	static const float2 Offsets[8] =
 	{
 		float2( 0,  0),
-		float2( 2, -2),
-		float2(-2, -2),
-		float2( 0,  2),
-		float2(-2,  0),
-		float2( 0, -2),
-		float2( 2,  0),
-		float2( 2,  2),
+		float2( 1, -1),
+		float2(-1, -1),
+		float2( 0,  1),
+		float2(-1,  0),
+		float2( 0, -1),
+		float2( 1,  0),
+		float2( 1,  1),
 	};
 
-	float2 uv = input.TexCoord;
-
 	// Inputs:
 	// Texture0 - ray trace buffer (xy: HDR color, z: weight)
 
 	// Sample GBuffer
 	GBufferData gBufferData = GetGBufferData();
-	GBufferSample gBuffer = SampleGBuffer(gBufferData, uv);
+	GBufferSample gBuffer = SampleGBuffer(gBufferData, input.TexCoord);
+    BRANCH
     if (gBuffer.ShadingModel == SHADING_MODEL_UNLIT)
         return 0;
 
 	// Randomize it a little
-	float2 random = RandN2(uv + TemporalTime);
+	float2 random = RandN2(input.TexCoord + TemporalTime);
 	float2 blueNoise = random.xy * 2.0 - 1.0;
 	float2x2 offsetRotationMatrix = float2x2(blueNoise.x, blueNoise.y, -blueNoise.y, blueNoise.x);
 
@@ -189,9 +218,9 @@ float4 PS_ResolvePass(Quad_VS2PS input) : SV_Target0
 	UNROLL
 	for (int i = 0; i < RESOLVE_SAMPLES; i++)
 	{
-		float2 offsetUV = Offsets[i] * SSRtexelSize;
+		float2 offsetUV = Offsets[i] * SSRTexelSize;
 		offsetUV =  mul(offsetRotationMatrix, offsetUV);
-		float4 value = Texture0.SampleLevel(SamplerLinearClamp, uv + offsetUV, 0);
+		float4 value = Texture0.SampleLevel(SamplerLinearClamp, input.TexCoord + offsetUV, 0);
 #if SSR_REDUCE_HIGHLIGHTS
 		value.rgb /= 1 + Luminance(value.rgb);
 #endif
@@ -224,8 +253,8 @@ float4 PS_TemporalPass(Quad_VS2PS input) : SV_Target0
 	float2 velocity = Texture2.SampleLevel(SamplerLinearClamp, uv, 0).xy;
 	float2 prevUV = uv - velocity;
 	float4 current = Texture0.SampleLevel(SamplerLinearClamp, uv, 0);
-	float2 du = float2(SSRtexelSize.x, 0.0);
-	float2 dv = float2(0.0, SSRtexelSize.y);
+	float2 du = float2(SSRTexelSize.x, 0.0);
+	float2 dv = float2(0.0, SSRTexelSize.y);
 
 	// Sample pixels around
 	float4 currentTopLeft = Texture0.SampleLevel(SamplerLinearClamp, uv.xy - dv - du, 0);

Source/ThirdParty/FidelityFX/FidelityFX.Build.cs

@@ -0,0 +1,22 @@
+// Copyright (c) Wojciech Figat. All rights reserved.
+
+using Flax.Build;
+using Flax.Build.NativeCpp;
+
+/// <summary>
+/// https://github.com/GPUOpen-LibrariesAndSDKs/FidelityFX-SDK
+/// </summary>
+public class FidelityFX : HeaderOnlyModule
+{
+    /// <inheritdoc />
+    public override void Init()
+    {
+        base.Init();
+
+        LicenseType = LicenseTypes.MIT;
+        LicenseFilePath = "license.txt";
+
+        // Merge third-party modules into engine binary
+        BinaryModuleName = "FlaxEngine";
+    }
+}

Source/ThirdParty/FidelityFX/ffx_sssr.h

@@ -0,0 +1,131 @@
+/**********************************************************************
+Copyright (c) 2021 Advanced Micro Devices, Inc. All rights reserved.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+********************************************************************/
+
+#ifndef FFX_SSSR
+#define FFX_SSSR
+#define FFX_SSSR_FLOAT_MAX                          3.402823466e+38
+
+void FFX_SSSR_InitialAdvanceRay(float3 origin, float3 direction, float3 inv_direction, float2 current_mip_resolution, float2 current_mip_resolution_inv, float2 floor_offset, float2 uv_offset, out float3 position, out float current_t) {
+    float2 current_mip_position = current_mip_resolution * origin.xy;
+
+    // Intersect ray with the half box that is pointing away from the ray origin.
+    float2 xy_plane = floor(current_mip_position) + floor_offset;
+    xy_plane = xy_plane * current_mip_resolution_inv + uv_offset;
+
+    // o + d * t = p' => t = (p' - o) / d
+    float2 t = xy_plane * inv_direction.xy - origin.xy * inv_direction.xy;
+    current_t = min(t.x, t.y);
+    position = origin + current_t * direction;
+}
+
+bool FFX_SSSR_AdvanceRay(float3 origin, float3 direction, float3 inv_direction, float2 current_mip_position, float2 current_mip_resolution_inv, float2 floor_offset, float2 uv_offset, float surface_z, inout float3 position, inout float current_t) {
+    // Create boundary planes
+    float2 xy_plane = floor(current_mip_position) + floor_offset;
+    xy_plane = xy_plane * current_mip_resolution_inv + uv_offset;
+    float3 boundary_planes = float3(xy_plane, surface_z);
+
+    // Intersect ray with the half box that is pointing away from the ray origin.
+    // o + d * t = p' => t = (p' - o) / d
+    float3 t = boundary_planes * inv_direction - origin * inv_direction;
+
+    // Prevent using z plane when shooting out of the depth buffer.
+#ifdef FFX_SSSR_INVERTED_DEPTH_RANGE
+    t.z = direction.z < 0 ? t.z : FFX_SSSR_FLOAT_MAX;
+#else
+    t.z = direction.z > 0 ? t.z : FFX_SSSR_FLOAT_MAX;
+#endif
+
+    // Choose nearest intersection with a boundary.
+    float t_min = min(min(t.x, t.y), t.z);
+
+#ifdef FFX_SSSR_INVERTED_DEPTH_RANGE
+    // Larger z means closer to the camera.
+    bool above_surface = surface_z < position.z;
+#else
+    // Smaller z means closer to the camera.
+    bool above_surface = surface_z > position.z;
+#endif
+
+    // Decide whether we are able to advance the ray until we hit the xy boundaries or if we had to clamp it at the surface.
+    // We use the asuint comparison to avoid NaN / Inf logic, also we actually care about bitwise equality here to see if t_min is the t.z we fed into the min3 above.
+    bool skipped_tile = asuint(t_min) != asuint(t.z) && above_surface; 
+
+    // Make sure to only advance the ray if we're still above the surface.
+    current_t = above_surface ? t_min : current_t;
+
+    // Advance ray
+    position = origin + current_t * direction;
+
+    return skipped_tile;
+}
+
+float2 FFX_SSSR_GetMipResolution(float2 screen_dimensions, int mip_level) {
+    return screen_dimensions * pow(0.5, mip_level);
+}
+
+// Requires origin and direction of the ray to be in screen space [0, 1] x [0, 1]
+float3 FFX_SSSR_HierarchicalRaymarch(Texture2D depthBuffer, uint hzbMips, float depthDiffError, out bool uncertainHit, float3 origin, float3 direction, float2 screen_size, int most_detailed_mip, uint max_traversal_intersections, out bool valid_hit) {
+    const float3 inv_direction = select(direction != 0, 1.0 / direction, FFX_SSSR_FLOAT_MAX);
+
+    // Start on mip with highest detail.
+    int current_mip = most_detailed_mip;
+
+    // Could recompute these every iteration, but it's faster to hoist them out and update them.
+    float2 current_mip_resolution = FFX_SSSR_GetMipResolution(screen_size, current_mip);
+    float2 current_mip_resolution_inv = rcp(current_mip_resolution);
+
+    // Offset to the bounding boxes uv space to intersect the ray with the center of the next pixel.
+    // This means we ever so slightly over shoot into the next region. 
+    float2 uv_offset = 0.005 * exp2(most_detailed_mip) / screen_size;
+    uv_offset = select(direction.xy < 0, -uv_offset, uv_offset);
+
+    // Offset applied depending on current mip resolution to move the boundary to the left/right upper/lower border depending on ray direction.
+    float2 floor_offset = select(direction.xy < 0, 0, 1);
+    
+    // Initially advance ray to avoid immediate self intersections.
+    float current_t;
+    float3 position;
+    FFX_SSSR_InitialAdvanceRay(origin, direction, inv_direction, current_mip_resolution, current_mip_resolution_inv, floor_offset, uv_offset, position, current_t);
+
+    uint overDiffError = 0;
+    int i = 0;
+    while (i < max_traversal_intersections && current_mip >= most_detailed_mip) {
+        float2 current_mip_position = current_mip_resolution * position.xy;
+        float surface_z = depthBuffer.Load(int3(current_mip_position, current_mip)).x;
+        if (position.z - surface_z > depthDiffError) overDiffError++; // Count number of times we were under the depth by more than the allowed error
+        bool skipped_tile = FFX_SSSR_AdvanceRay(origin, direction, inv_direction, current_mip_position, current_mip_resolution_inv, floor_offset, uv_offset, surface_z, position, current_t);
+        ++i;
+        if (!skipped_tile || current_mip < hzbMips) // Never go too low depth resolution to avoid blocky artifacts
+        {
+            current_mip += skipped_tile ? 1 : -1;
+            current_mip_resolution *= skipped_tile ? 0.5 : 2;
+            current_mip_resolution_inv *= skipped_tile ? 2 : 0.5;
+        }
+    }
+
+    valid_hit = (i <= max_traversal_intersections);
+    uncertainHit = valid_hit && overDiffError > 3; // If we went over under the surface to detect uncertain hits
+
+    return position;
+}
+
+#endif //FFX_SSSR

Source/ThirdParty/FidelityFX/license.txt

@@ -0,0 +1,19 @@
+Copyright (c) 2021 Advanced Micro Devices, Inc. All rights reserved.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.