Restir DI implementation using Nvidia Falcor

This repository host a C++ implementation of the Restir algorithm inside Falcor 8.0.

Video showcase: https://www.youtube.com/watch?v=pyQrblYP_VY

Source code: https://github.com/Trylz/Restir_CPP/tree/main/Source/Samples/Restir

Here the original paper: https://research.nvidia.com/sites/default/files/pubs/2020-07_Spatiotemporal-reservoir-resampling/ReSTIR.pdf

How to test

Grab necessary assets

The dragon buddha model used is huge. Git doesnt allow me to push files that are greater than 100 MB. That model need to be installed has explained here: https://github.com/Trylz/Restir_CPP/blob/main/TestScenes/DragonBuddha/README.txt

Controls

W, A, S, D, Q, E
Z, Q, S, D, A, E for Azerty keyboard

Mouse left click for rotation.

Building prerequisites

• Windows 10 version 20H2 (October 2020 Update) or newer, OS build revision .789 or newer

• Visual Studio 2022: https://aka.ms/vs/17/release/vs_community.exe

• Cmake

• Windows 10 SDK (10.0.19041.0) for Windows 10, version 2004

• Cuda toolkit installed. Right now 12.6(https://developer.nvidia.com/cuda-12-6-0-download-archive) is hardcoded set(CMAKE_CUDA_COMPILER "C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v12.6/bin") in root CMakeLists.txt
  You may want to change this to your current cuda installation but note that only 12.6 was tested.
  This mean your CUDA_PATH environment variable should look something like this C:/Program Files/NVIDIA GPU Computing Toolkit/CUDA/v12.6

• An Nvidia GPU since Cuda is used

• A GPU which supports DirectX Raytracing, such as the NVIDIA Titan V or GeForce RTX

• NVIDIA driver 466.11 or newer

Building Restir Falcor

• Run the setup_vs2022.bat script after cloning this repository. The solution files are written to build/windows-vs2022.
• Open the Falcor.sln solution
• Set Samples/Restir as your startup project
• Set your configuration to Release(Unless you are debbuging)
• Build and run

Test scenes

Three test scenes are provided. The Arcade scene that ships with Falcor, the Sponza scene and the DragonBuddha scene.
To switch scene simply change the SCENE_NAME define inside RestirApp.cpp file
0: Arcade scene
1: Dragon buddha scene.
2: Sponza scene.

Code overview

Restir specific source code is located here
https://github.com/Trylz/Restir_DI_CPP/tree/main/Source/Samples/Restir

Application entry point

The application entry point is located in the RestirApp.cpp file

Reservoirs

Reservoirs are managed by the reservoir manager. See ReservoirManager.cpp.

Lights

Lights are managed by the light manager. See LightManager.cpp.
This is where lights are created for each scene.
Right now only spherical(so area) lights are supported.

Settings

Scenes specific tweaks are stored in the SceneSettings struct.

Render passes

GBuffer

GBuffer rendering is the first pass. It is generated by raytracing. See GBuffer.cpp.
Should ideally be done by rasterization to save time. This is WIP see: #2

RIS

Resampled Importance Sampling is performed as described in paper. See RISPass.cpp

Visibility test

For each reservoir its weight is set to zero if occluded. So raytracing is performed here. See VisibilityPass.cpp

Temporal filtering

#define USE_TEMPORAL_FILTERING 1
We combine the current frame reservoirs with thoses of the previous frame. See TemporalFilteringPass.cpp

Here the dragon buddha scene with temporal filtering ON and OFF

ON: https://youtu.be/8Q-eVLcEUPY

OFF: https://youtu.be/iBL5fuxIujA

Spatial filtering

#define USE_SPATIAL_FILTERING 0
Combine each pixel reservoirs with thoses of its neighbors. This is disabled by default since i dont see any gain using it.
See SpatialFilteringPass.cpp

Shading

Shading is performed using the reservoirs from the previous passes. See ShadingPass.cpp.

Denoising

#define USE_DENOISING 1

Denoising can be done using NRD or Optix denoiser
#define DENOISING_NRD 0

Note that NRD is currently performed on the final image(same for Optix). It is not recommended when i read the doc. So we may want to denoise the reservoirs instead? This is being investigated here: https://github.com/Trylz/Restir_DI_CPP/tree/NRD-before-shading

CURRENT ISSUES

This is work in progress and some artefacts are still visible.

1) Temporal acnee

Acnee with denoising OFF in Sponza scene

CONCLUSION

There is still work to be done to have a production ready implementation. Performance wise a i am getting decent results for a raytracer.