RTXDI SDK and Sample Applications

Version 2.0.0.

Change Log

Introduction

RTX Direct Illumination is a framework that facilitates the implementations of efficient direct light sampling in real-time renderers. It is based on the ReSTIR algorithm published in the paper called "Spatiotemporal reservoir resampling for real-time ray tracing with dynamic direct lighting" by B. Bitterli et al.

Starting with version 2.0, RTXDI also includes ReSTIR GI functionality, which allows applications to apply importance resampling to indirect illumination rendered using path tracing. For more information about the indirect illumination algorithm, see the paper called "ReSTIR GI: Path Resampling for Real-Time Path Tracing" by Y. Ouyang et al. The feature is described in more detail in this document.

For more information about RTXDI, see the NVIDIA Developer Page.

Package Contents

rtxdi-sdk contains the SDK source code files that are meant to be included into the application build:

• rtxdi-sdk/include has the include files, both for host code and for shaders
• rtxdi-sdk/include/rtxdi/ResamplingFunctions.hlsli is the main shader include file that contains the resampling implementation
• rtxdi-sdk/shaders has the shader files that are supposed to be compiled through whatever means the application normally uses
• rtxdi-sdk/src has the host code with various utility functions for setting up the parameters and resources for resampling

src contains the sample application host code.

shaders contains the sample application shaders.

donut is a submodule structure with the "Donut" rendering framework used to build the sample apps.

NRD is a submodule with the "NRD" denoiser library.

DLSS is a submodule with the Deep Learning Super-Sampling SDK.

Additional contents delivered through packman:

dxc is a recent version of DirectX Shader Compiler;

media contains the media files necessary for the sample apps to run.

Building and Running the Sample Apps

Windows

1. Clone the repository with all submodules:

   • git clone --recursive https://github.com/NVIDIAGameWorks/RTXDI.git

   If the clone was made non-recursively and the submodules are missing, clone them separately:

   • git submodule update --init --recursive

2. Pull the media files and DXC binaries from packman:

   • update_dependencies.bat

3. Configure the solution with CMake. The easiest option is to use CMake GUI.

4. Assuming that the RTXDI SDK tree is located in D:\RTXDI, set the following parameters in the GUI:

   • "Where is the source code" to D:\RTXDI
   • "Where to build the binaries" to D:\RTXDI\build

5. Click "Configure", set "Generator" to the Visual Studio you're using (tested with VS 2019 version 16.8.2), set "Optional platform" to x64, click "Finish".

6. Click "Generate", then "Open Project".

7. Build the solution with Visual Studio

8. Run the rtxdi-sample or minimal-sample projects.

Linux

1. Make sure the necessary build packages are installed on the target system. For Ubuntu 20.04 (amd64), the following command is sufficient:

   • sudo apt install build-essential cmake xorg-dev libtinfo5

2. Clone the repository with all submodules:

   • git clone --recursive https://github.com/NVIDIAGameWorks/RTXDI.git

   If the clone was made non-recursively and the submodules are missing, clone them separately:

   • git submodule update --init --recursive

3. Pull the media files and DXC binaries from packman:

   • cd RTXDI && ./update_dependencies.sh

4. Create a build folder:

   • mkdir build && cd build

5. Configure the project with CMake:

   • cmake ..

6. Build:

   • make -j8 (example for an 8-core CPU, or use Ninja instead)

7. Run:

   • bin/rtxdi-sample or bin/minimal-sample

Vulkan support

The RTXDI sample applications can run using D3D12 or Vulkan, which is achieved through the NVRHI rendering API abstraction layer and HLSL shader compilation to SPIR-V through DXC (DirectX Shader Compiler). We deliver a compatible version of DXC through packman. If you wish to use a different (e.g. newer) version of DXC, it can be obtained from Microsoft/DirectXShaderCompiler on GitHub. The path to a custom version of DXC can be configured using the DXC_PATH and DXC_SPIRV_PATH CMake variables.

By default, the sample apps will run using D3D12 on Windows. To start them in Vulkan mode, add --vk to the command line. To compile the sample apps without Vulkan support, set the CMake variable DONUT_WITH_VULKAN to OFF and re-generate the project.

Integration

See the Integration Guide.