UnityPathTracing

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A real-time path tracing rendering system built in Unity URP, replicating the core features of NVIDIA NRDSample, RTXDI, RTXPT, and other RTX technologies, with optimizations and extensions for the Unity environment. Primarily serves as an experimental playground for various RTX-related technologies in Unity.

At its core, a native rendering plugin based on shader reflection information is implemented, enabling arbitrary shaders to be compiled with arbitrary parameters and used within Unity. This makes it possible to leverage various DX12 features — including custom acceleration structures, SER, OMM, and Bindless — directly in Unity.

Five RenderFeatures are currently implemented: native and Unity versions of NrdSampleFeature, native and Unity versions of RtxdiFeature, and RtxPt.

The native NrdSampleFeature has been highly optimized to work with Unity's multi-threaded rendering, achieving performance nearly identical to the original NRD-Sample.

The RtxPt version is also nearly identical in performance to the original, with good support for Unity's various analytic lights. However, its performance is lower than NrdSample and it relies more heavily on DLSS RR.

Blog post: NRDSample Implementation in Unity

Blog post: RTXDI Implementation in Unity

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How to Run

Prerequisites

• Git ≥ 2.46 with Git LFS installed. Older versions (e.g. 2.45) reject the Git LFS post-checkout hook the RTXPT-Assets repo ships with and restore_rtxpt_assets.py fails with "fatal: active post-checkout hook found during git clone". Upgrading Git resolves it.
• Python 3 with Pillow for the DDS → PNG conversion in restore_nrdsample_assets.py:

  pip install Pillow

git clone https://github.com/Kuan-Mi/UnityPathTracing
cd UnityPathTracing
build_and_copy.bat
python tools\restore_rtxpt_assets.py
python tools\restore_nrdsample_assets.py

Upgrade Unity's built-in Agility SDK to 1.619.1

The Unity editor ships with an older Agility SDK. You need to upgrade it to version 1.619.1 by patching the editor executable and replacing the D3D12 runtime DLLs.

You can do this manually by hex-editing the Unity executable (change the SDK version constant from 618 to 619) and then downloading D3D12Core.dll and d3d12SDKLayers.dll from the Microsoft.Direct3D.D3D12 NuGet package and replacing the files in the D3D12/ folder next to the Unity executable.

Alternatively, use the provided PowerShell script patch.ps1, which automates both steps:

1. Opens a file picker — select your Unity.exe (e.g. C:\Program Files\Unity\Hub\Editor\6000.3.17f1\Editor\Unity.exe)
2. Patches the SDK version constant in the binary in-place
3. Downloads Agility SDK 1.619.1 from NuGet and overwrites D3D12Core.dll / d3d12SDKLayers.dll in the adjacent D3D12\ folder
4. Backs up all modified files as .bak before overwriting

powershell -ExecutionPolicy Bypass -File patch.ps1

Note: Run PowerShell as Administrator if UAC prevents writing to Program Files.

Note: The built game executable also needs to be patched. Run patch.ps1 again and select the .exe in your build output folder. The D3D12\ folder will be created automatically next to it.

Running a Scene

Open the Unity editor and open the Assets/RTXPT/Assets/ConvergenceTest.unity scene to see the default RtxPt result.

NRD-Sample, RTXDI, and RTXPT are split into three folders. The scene files in each folder only render correctly when their corresponding Renderer is assigned in Assets/Settings/RPAsset.asset.

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Requirements

• GPU: NVIDIA RTX GPU with DXR support (RTX 3060 or above recommended)
• Unity Version: 6000.3.17

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Acknowledgements

Thanks to inedelcu for the great help with writing ray tracing shaders and handling acceleration structures.

References

NRD-Sample

RTXGI

RTXDI

RTXPT

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在 Unity URP 中实现的实时路径追踪渲染系统，复刻了 NVIDIA NRDSample、RTXDI、RTXPT等核心功能，并针对 Unity 环境进行了优化和扩展。主要是试验各种RTX相关技术在Unity中的使用。

其中实现了一个基于Shader反射信息的原生渲染插件，可以以任意参数编译任意着色器并在Untiy中使用，这使得自定义加速结构、SER、OMM、Bindless等各种dx12特性可以在Unity中使用。

目前实现了五个RenderFeature，分别是原生/untiy版本的NrdSampleFeature，原生/Unity版本的RtxdiFeature，以及RtxPt。

其中原生版本的NrdSampleFeature经过高度优化，可以适配unity的多线程渲染，性能和原版（NrdSample）几乎一致

Rtxpt版本也几乎和原版性能一致，且对Unity的各种分析光源支持较好，但性能不如NrdSample，比较依赖DLSSRR。

详见博客：NRDSample 在 Unity 中的实现

详见博客：RTXDI 在 Unity 中的实现

如何运行

前置依赖

• Git ≥ 2.46，并安装 Git LFS。旧版本（如 2.45）会拒绝 RTXPT-Assets 仓库自带的 Git LFS post-checkout 钩子，导致 restore_rtxpt_assets.py 报错 "fatal: active post-checkout hook found during git clone"。升级 Git 即可解决。
• Python 3 并安装 Pillow，用于 restore_nrdsample_assets.py 中的 DDS → PNG 转换：

  pip install Pillow

git clone https://github.com/Kuan-Mi/UnityPathTracing
cd UnityPathTracing
build_and_copy.bat
python tools\restore_rtxpt_assets.py
python tools\restore_nrdsample_assets.py

将 Unity 内置的 Agility SDK 升级至 1.619.1

Unity 编辑器自带的 Agility SDK 版本较旧，需要升级至 1.619.1。

你可以手动完成此操作：用十六进制编辑器修改 Unity 可执行文件中的版本常量（将 618 改为 619），然后从 Microsoft.Direct3D.D3D12 NuGet 包 下载 D3D12Core.dll 和 d3d12SDKLayers.dll，并替换 Unity 可执行文件同级目录下 D3D12\ 文件夹中的对应文件。

也可以使用项目提供的 PowerShell 脚本 patch.ps1，它会自动完成以上所有步骤：

1. 弹出文件选择框，选择你的 Unity.exe（例如 C:\Program Files\Unity\Hub\Editor\6000.3.17f1\Editor\Unity.exe）
2. 自动修改可执行文件中的 SDK 版本常量
3. 从 NuGet 下载 Agility SDK 1.619.1，并覆盖同级 D3D12\ 目录中的 DLL 文件
4. 所有被修改的文件在覆盖前均会备份为 .bak

powershell -ExecutionPolicy Bypass -File patch.ps1

注意：如果 UAC 阻止写入 Program Files 目录，请以管理员身份运行 PowerShell。

注意：打包后的游戏可执行文件同样需要修改。再次运行 patch.ps1，选择打包输出目录中的 .exe 文件即可，D3D12\ 文件夹会自动创建在其同级目录下。

运行场景

打开Unity编辑器，打开 Assets/RTXPT/Assets/ConvergenceTest.unity 场景，即可看到默认的Rtxpt的效果。

NRD-Sample、RTXDI、RTXPT分为三个文件夹，每个文件夹中对应的场景文件只有其Renderer被放置在Assets/Settings/RPAsset.asset中才能正确显示。

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要求

• GPU：支持 DXR 的 NVIDIA RTX 显卡（如 RTX 3060 及以上）
• Untiy版本: 6000.3.17

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致谢

感谢 inedelcu 的帮助，在编写光追着色器和处理加速结构方面帮了我很多。

参考

NRD-Sample

RTXGI

RTXDI

RTXPT

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