FidelityFX Hybrid Shadows

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This sample demonstrates the use of the FidelityFX Classifier and FidelityFX Denoiser techniques.

For details on the techniques that underpins the FidelityFX Hybrid Reflections effect you can refer to the respective FidelityFX Classifier documentation and FidelityFX Denoiser documentation .

Slides which review the main steps of FidelityFX Hybrid Shadows sample can be found here.


Windows DirectX(R)12 Vulkan(R)

UI elements

The sample contains various UI elements to help you explore the techniques it demonstrates. The table below summarises the UI elements and what they control within the sample.


Element name



Run Hybrid Shadow


Enable/Disable the hybrid shadows.

Use Denoiser


Enable/Disable the shadow denoiser.

Sun Solid Angle

0.0 - 1.0

Controls the size of the sun light.

Debug Mode

Disabled, Show RayTraced Tiles, Show Ray minT, Show Ray maxT, Show Ray length, Show RayTracing Texture

Used to select the debug output view.


0 - 32

Used to discard a tile where not enough rays need to be traced in the FidelityFX Classifier.

PCF Offset


Used to offset the blocker depth value in the FidelityFX Classifier.

Reject Lit Pixels for Ray Tracing


Used to discard pixels for ray tracing that are in lit areas in the FidelityFX Classifier.

Use Shadow Maps to determine RayT


Enable/Disable the use of shadow maps to determine ray properties.

Setting up FidelityFX Hybrid Shadows

The FidelityFX Hybrid Shadows sample uses FidelityFX Classifier to generate a list of tiles on the screen from which a ray tracing kernel can be launched. Then, the FidelityFX Denoiser can be enabled to remove noise from the raw, 1 sample per pixel ray tracing output.

Setting up classifier

Include the interface for the backend of the FidelityFX Classifier API.


#include <FidelityFX/host/ffx_classifier.h>

Create FidelityFX Classifier context


m_ClassifierCtxDesc.flags = FFX_CLASSIFIER_SHADOW ;
m_ClassifierCtxDesc.resolution.width = resInfo.RenderWidth;
m_ClassifierCtxDesc.resolution.height = resInfo.RenderHeight;
m_ClassifierCtxDesc.flags |= GetConfig ()->InvertedDepth  ? FFX_CLASSIFIER_ENABLE_DEPTH_INVERTED  : 0;
m_ClassifierCtxDesc.backendInterface = backendInterface;
FFX_ASSERT(ffxClassifierContextCreate (&m_ClassifierContext, &m_ClassifierCtxDesc) == FFX_OK );

Set up the dispatch parameters and dispatch


FfxClassifierShadowDispatchDescription  shadowClassifierDispatchParams = {};
shadowClassifierDispatchParams.commandList  = ffxGetCommandList(pCmdList);
FFX_ASSERT(FFX_OK  == ffxClassifierContextShadowDispatch (&m_ClassifierContext, &shadowClassifierDispatchParams));

Setting up the FidelityFX Denoiser

Include the interface for the backend of the FidelityFX Denoiser API.



#include <FidelityFX/host/ffx_denoiser.h>

Create FidelityFX Denoiser context


m_DenoiserCtxDesc.flags = FFX_DENOISER_SHADOWS ;
m_DenoiserCtxDesc.windowSize.width = resInfo.RenderWidth;
m_DenoiserCtxDesc.windowSize.height = resInfo.RenderHeight;
m_DenoiserCtxDesc.flags |= GetConfig ()->InvertedDepth  ? FFX_CLASSIFIER_ENABLE_DEPTH_INVERTED  : 0;
m_DenoiserCtxDesc.backendInterface = backendInterface;
FFX_ASSERT(ffxDenoiserContextCreate (&m_DenoiserContext, &m_DenoiserCtxDesc) == FFX_OK );

Set up the dispatch parameters and dispatch


FfxDenoiserShadowsDispatchDescription  denoiserDispatchDescription = {};
denoiserDispatchDescription.commandList  = ffxGetCommandList(pCmdList);
FFX_ASSERT(FFX_OK  == ffxDenoiserContextDispatchShadows (&m_DenoiserContext, &denoiserDispatchDescription));

Sample Controls and Configurations

For sample controls, configuration and Cauldron UI element details, please see Running the samples

See Also