Falcor-7.0-Tutorial

This is a tutorial of how to use Falcor 7.0 to self-define a render pass. Although there is a turotial on writing shaders and define a render pass in the original github repo, the code in the original tutorial (markdown files) is not compatible with the newly updated version of Falcor. So I created this repo to rewrite the tutorial based on the newly updated Falcor API.

Specifically, this tutorial mainly tells about how to create a wireframe render pass like the picture above.

Download & Install

Prequisites

Please follow the original repository to prepare needed prequisites.

Clone the repository

git clone --recursive https://github.com/NVIDIAGameWorks/Falcor.git

Setup and Build

Run the setup bash script in the terminal.

./setup_vs2022.bat

[Important] Before build the project, please change all the in each .vsxproj file, otherwise the building process will fail. And there is a quick way of doing this: use vscode to open the folder Falcor\build\windows-vs2022\Source and search for <TreatWarningAsError>true and replace them all with <TreatWarningAsError>false.

After this operation, build this project in the terminal.

cmake --build build/windows-vs2022

Create the WireframePass

Create the pass using the given tool

Run this command in the terminal and a new pass folder will be created automatically in Falcor/Source/RenderPasses.

./tools/make_new_render_pass.bat WireframePass

Coding the pass

This part will give different code from the tutorial in the original repository, because we adapt to the new api and make some changes accordingly to make the WireframePass work.

1. Create the shader file as Falcor/Source/RenderPasses/WireframePass/WireframePass.3d.slang

   import Scene.Raster;
   
   cbuffer PerFrameCB
   {
      float4 gColor;
   };
   
   VSOut vsMain(VSIn vIn)
   {
      return defaultVS(vIn);
   }
   
   float4 psMain() : SV_Target
   {
      return gColor;
   }

2. Create a namespace in Falcor/Source/RenderPasses/WireframePass/WireframePass.cpp to store the parameters commonly used in this script.

   namespace {
      const char kShaderFile[] = "RenderPasses/WireframePass/WireframePass.3d.slang";
   }

   Note: if the compiled program can not find the shader file, change the path to absolute path.

3. Add private variables to Falcor/Source/RenderPasses/WireframePass/WireframePass.h

   ref<Scene> mpScene;
   ref<Program> mpProgram;
   ref<GraphicsState> mpGraphicsState;
   ref<RasterizerState> mpRasterState;
   ref<ProgramVars> mpVars;
   ref<Fbo> mpFbo;

4. WireframePass()

   WireframePass::WireframePass(ref<Device> pDevice, const Properties& props) : RenderPass(pDevice) {
      RasterizerState::Desc wireframeDesc;
      wireframeDesc.setFillMode(RasterizerState::FillMode::Wireframe);
      wireframeDesc.setCullMode(RasterizerState::CullMode::None);
      mpRasterState = RasterizerState::create(wireframeDesc);
   
      mpGraphicsState = GraphicsState::create(mpDevice);
   
      mpFbo = Fbo::create(mpDevice);
   }

5. reflect()

   RenderPassReflection WireframePass::reflect(const CompileData& compileData)
   {
      // Define the required resources here
      RenderPassReflection reflector;
      reflector.addOutput("output", "Wireframe view texture");
      return reflector;
   }

6. setScene()

   void WireframePass::setScene(RenderContext* pRenderContext, const ref<Scene>& pScene)
   {
      mpScene = pScene;
   
      if (mpScene != nullptr) {
          // Create wireframe program
          ProgramDesc desc;
          desc.addShaderModules(mpScene->getShaderModules());
          desc.addShaderLibrary(kShaderFile).vsEntry("vsMain").psEntry("psMain");
          desc.addTypeConformances(mpScene->getTypeConformances());
   
          mpProgram = Program::create(mpDevice, desc, mpScene->getSceneDefines());
          mpGraphicsState->setProgram(mpProgram);
   
          mpVars = ProgramVars::create(mpDevice, mpProgram.get());
      }
   }

7. execute()

   void WireframePass::execute(RenderContext* pRenderContext, const RenderData& renderData)
   {
      auto pTex = renderData.getTexture("output");
      mpFbo->attachColorTarget(pTex, uint32_t(0));
      const float4 clearColor(0, 0, 0, 1);
      pRenderContext->clearFbo(mpFbo.get(), clearColor, 1.0f, 0, FboAttachmentType::All);
      mpGraphicsState->setFbo(mpFbo);
   
      if (mpScene) {
          mpVars->getRootVar()["PerFrameCB"]["gColor"] = float4(0, 1, 0, 1);
          mpScene->rasterize(pRenderContext, mpGraphicsState.get(), mpVars.get(), mpRasterState, mpRasterState);
      }
   }

8. Create the WireframePass.py for Falcor to loading the render graph in Falcor/scripts/WireframePass.py

   import falcor
   
   def render_graph_WireframePass():
      g = RenderGraph("WireframePass")
      WireframePass = createPass("WireframePass")
      g.addPass(WireframePass, "WireframePass")
      g.markOutput("WireframePass.output")
      return g
   
   WireframPass = render_graph_WireframePass()
   try: m.addGraph(WireframPass)
   except NameError: None

Rebuild the project

Since a new pass has been added as a part of the source code, we need to Setup and Build again. Just follow the steps above.

Run the WireframePass

1. Open build\windows-vs2022\bin\Debug\Mogwai.exe and hit File->Loading Script, select the WireframePass.py we just created.
2. Hit File->Loading Scene, select media\Arcade\Arcade.pyscene, and the wireframe renderpass will show up in the window.