# BozoShaderDemo

VTKExamples/Cxx/Shaders/BozoShaderDemo

### Code

BozoShaderDemo.cxx

    #include <vtkSmartPointer.h>

    #include <vtkCamera.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkShaderProgram.h>
    #include <vtkActor.h>
    #include <vtkActor2D.h>
    #include <vtkOpenGLPolyDataMapper.h>
    #include <vtkProperty.h>
    #include <vtkPolyDataNormals.h>
    #include <vtkTextProperty.h>
    #include <vtkTextMapper.h>

    #include <vtkTransform.h>
    #include <vtkTransformPolyDataFilter.h>
    #include <vtkTriangleMeshPointNormals.h>
    #include <vtkTriangleFilter.h>

    #include <vtkNamedColors.h>
    #include <vtkRenderWindowInteractor.h>

    #include <vtksys/SystemTools.hxx>
    #include <vtkBYUReader.h>
    #include <vtkOBJReader.h>
    #include <vtkPLYReader.h>
    #include <vtkPolyDataReader.h>
    #include <vtkSTLReader.h>
    #include <vtkXMLPolyDataReader.h>
    #include <vtkSphereSource.h>

    #include <fstream>
    #include <sstream>

    namespace
    {
    // -----------------------------------------------------------------------
    // Update a uniform in the shader for each render. We do this with a
    // callback for the UpdateShaderEvent
    class vtkShaderCallback : public vtkCommand
    {
    public:
      static vtkShaderCallback *New()
        { return new vtkShaderCallback; }
      vtkRenderer *Renderer;
      float k;
      void Execute(vtkObject *, unsigned long, void* calldata) override
      {
        vtkShaderProgram *program = reinterpret_cast<vtkShaderProgram*>(calldata);
        if (program)
        {
          program->SetUniformf("k", k);
        }
      }
      void Print(std::ostream &os)
      {
        os << "k: " << k << std::endl;
      }

      vtkShaderCallback()
      {
        this->Renderer = nullptr;
        this->k = 5;
      }

    };
    }

    namespace
    {
    vtkSmartPointer<vtkPolyData> ReadPolyData(const char *fileName);
    }

    //----------------------------------------------------------------------------
    int main(int argc, char *argv[])
    {
      if (argc < 2)
      {
        std::cout << "Usage: " << argv[0] << " PerlnNoise.glsl "
                  << "[polydataFile] "
                  << "[k(5)]" << std::endl;
        return EXIT_FAILURE;
      }
      vtkSmartPointer<vtkNamedColors> colors =
        vtkSmartPointer<vtkNamedColors>::New();

      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();

      // Create one text property for all
      vtkSmartPointer<vtkTextProperty> textProperty =
        vtkSmartPointer<vtkTextProperty>::New();
      textProperty->SetFontSize(20);
    //  textProperty->SetJustificationToCentered();
      textProperty->SetColor(0.3, 0.3, 0.3);

      std::vector<vtkSmartPointer<vtkRenderer>> renderers;
      for (int i = 2; i < argc; ++i)
      {
        std::cout << "Reading file: " << argv[i] << std::endl;
        vtkSmartPointer<vtkPolyData> polyData =
          ReadPolyData(argv[i]);
        std::ifstream shaderFile(argv[1]);
        std::ostringstream shaderCode;
        shaderCode << shaderFile.rdbuf();
        shaderFile.close();

        // Create a transform to rescale model
        double center[3];
        polyData->GetCenter(center);
        double bounds[6];
        polyData->GetBounds(bounds);
        double maxBound = std::max(std::max(bounds[1] - bounds[0],  bounds[3] - bounds[2]), bounds[5] - bounds[4]);

        // Create textActors
        vtkSmartPointer<vtkTextMapper> textMapper =
          vtkSmartPointer<vtkTextMapper>::New();
        textMapper->SetTextProperty(textProperty);
        textMapper->SetInput(vtksys::SystemTools::GetFilenameName(argv[i]).c_str());

        vtkSmartPointer<vtkActor2D> textActor =
          vtkSmartPointer<vtkActor2D>::New();
        textActor->SetMapper(textMapper);
        textActor->SetPosition(20, 20);

        vtkSmartPointer<vtkActor> actor =
          vtkSmartPointer<vtkActor>::New();
        vtkSmartPointer<vtkRenderer> renderer =
          vtkSmartPointer<vtkRenderer>::New();
        vtkSmartPointer<vtkOpenGLPolyDataMapper> mapper =
          vtkSmartPointer<vtkOpenGLPolyDataMapper>::New();
        renderer->SetBackground(colors->GetColor3d("Burlywood").GetData());

        renderers.push_back(renderer);
        renderWindow->AddRenderer(renderer);
        renderer->AddActor(actor);
        renderer->AddActor(textActor);

      // Rescale polydata to [-1,1]
      vtkSmartPointer<vtkTransform> userTransform =
        vtkSmartPointer<vtkTransform>::New();
      userTransform->Translate(-center[0], -center[1], -center[2]);
      userTransform->Scale(1.0/maxBound, 1.0/maxBound, 1.0/maxBound);
      vtkSmartPointer<vtkTransformPolyDataFilter> transform =
        vtkSmartPointer<vtkTransformPolyDataFilter>::New();
      transform->SetTransform(userTransform);
      transform->SetInputData(polyData);

      vtkSmartPointer<vtkTriangleFilter> triangles =
        vtkSmartPointer<vtkTriangleFilter>::New();
      triangles->SetInputConnection(transform->GetOutputPort());

      vtkSmartPointer<vtkTriangleMeshPointNormals> norms =
        vtkSmartPointer<vtkTriangleMeshPointNormals>::New();
      norms->SetInputConnection(triangles->GetOutputPort());

      mapper->SetInputConnection(norms->GetOutputPort());
      mapper->ScalarVisibilityOff();

      actor->SetMapper(mapper);
      actor->GetProperty()->SetAmbientColor(0.2, 0.2, 0.2);
      actor->GetProperty()->SetDiffuseColor(1.0, 1.0, 1.0);
      actor->GetProperty()->SetSpecularColor(1.0, 1.0, 1.0);
      actor->GetProperty()->SetSpecular(0.5);
      actor->GetProperty()->SetDiffuse(0.7);
      actor->GetProperty()->SetAmbient(0.1);
      actor->GetProperty()->SetSpecularPower(100.0);
      actor->GetProperty()->SetOpacity(1.0);

      renderer->ResetCamera();
      renderer->GetActiveCamera()->Zoom(1.2);

      // Modify the vertex shader to pass the position of the vertex
      mapper->AddShaderReplacement(
        vtkShader::Vertex,
        "//VTK::Normal::Dec", // replace the normal block
        true, // before the standard replacements
        "//VTK::Normal::Dec\n" // we still want the default
        "  out vec4 myVertexMC;\n"
        ,
        false // only do it once
        );
      mapper->AddShaderReplacement(
        vtkShader::Vertex,
        "//VTK::Normal::Impl", // replace the normal block
        true, // before the standard replacements
        "//VTK::Normal::Impl\n" // we still want the default
        "  myVertexMC = vertexMC;\n"
        ,
        false // only do it once
        );

      // Add the code to generate noise
      // These functions need to be defined outside of main. Use the System::Dec
      // to declare and implement
      mapper->AddShaderReplacement(
        vtkShader::Fragment,
        "//VTK::System::Dec",
        false, // before the standard replacements
        shaderCode.str(),
        false // only do it once
        );

      // Define varying and uniforms for the fragment shader here
      mapper->AddShaderReplacement(
        vtkShader::Fragment,  // in the fragment shader
        "//VTK::Normal::Dec", // replace the normal block
        true, // before the standard replacements
        "//VTK::Normal::Dec\n" // we still want the default
        "  varying vec4 myVertexMC;\n"
        "  uniform float k = 1.0;\n"
        ,
        false // only do it once
        );

      mapper->AddShaderReplacement(
        vtkShader::Fragment,  // in the fragment shader
        "//VTK::Light::Impl", // replace the light block
        false, // after the standard replacements
        "//VTK::Light::Impl\n" // we still want the default calc
        "#define pnoise(x) ((noise(x) + 1.0) / 2.0)\n"
        "  vec3 noisyColor;\n"
        "  noisyColor.r = noise(k * 10.0 * myVertexMC);\n"
        "  noisyColor.g = noise(k * 11.0 * myVertexMC);\n"
        "  noisyColor.b = noise(k * 12.0 * myVertexMC);\n"
        "  /* map ranges of noise values into different colors */\n"
        "  int i;\n"
        "  float lowerValue = .3;\n"
        "  float upperValue = .6;\n"
        "  for ( i=0; i<3; i+=1)\n"
        "  {\n"
        "    noisyColor[i] = (noisyColor[i] + 1.0) / 2.0;\n"
        "    if (noisyColor[i] < lowerValue) \n"
        "    {\n"
        "      noisyColor[i] = lowerValue;\n"
        "    }\n"
        "    else\n"
        "    {\n"
        "      if (noisyColor[i] < upperValue)\n"
        "      {\n"
        "        noisyColor[i] = upperValue;\n"
        "      }\n"
        "      else\n"
        "      {\n"
        "        noisyColor[i] = 1.0;\n"
        "      }\n"
        "    }\n"
        "  }\n"
        "  fragOutput0.rgb = opacity * vec3(ambientColor + noisyColor * diffuse + specular);\n"
        "  fragOutput0.a = opacity;\n"
        ,
        false // only do it once
        );
      vtkSmartPointer<vtkShaderCallback> myCallback =
        vtkSmartPointer<vtkShaderCallback>::New();
      myCallback->Renderer = renderer;
      myCallback->k = 1;
      mapper->AddObserver(vtkCommand::UpdateShaderEvent, myCallback);
      }

      // Setup viewports for the renderers
      int rendererSize = 250;
      unsigned int xGridDimensions = 3;
      unsigned int yGridDimensions = 3;
      renderWindow->SetSize(
        rendererSize * xGridDimensions, rendererSize * yGridDimensions);
      for (int row = 0; row < static_cast<int>(yGridDimensions); row++)
      {
        for (int col = 0; col < static_cast<int>(xGridDimensions); col++)
        {
          int index = row * xGridDimensions + col;
          // (xmin, ymin, xmax, ymax)
          double viewport[4] = {
            static_cast<double>(col) * rendererSize /
            (xGridDimensions * rendererSize),
            static_cast<double>(yGridDimensions - (row + 1)) * rendererSize /
            (yGridDimensions * rendererSize),
            static_cast<double>(col + 1) * rendererSize /
            (xGridDimensions * rendererSize),
            static_cast<double>(yGridDimensions - row) * rendererSize /
            (yGridDimensions * rendererSize)};
          renderers[index]->SetViewport(viewport);
        }
      }

      vtkSmartPointer<vtkRenderWindowInteractor>  interactor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      interactor->SetRenderWindow(renderWindow);

      renderWindow->Render();
      interactor->Start();

      return EXIT_SUCCESS;
    }

    namespace
    {
    vtkSmartPointer<vtkPolyData> ReadPolyData(const char *fileName)
    {
      vtkSmartPointer<vtkPolyData> polyData;
      std::string extension = vtksys::SystemTools::GetFilenameExtension(std::string(fileName));
      if (extension == ".ply")
      {
        vtkSmartPointer<vtkPLYReader> reader =
          vtkSmartPointer<vtkPLYReader>::New();
        reader->SetFileName (fileName);
        reader->Update();
        polyData = reader->GetOutput();
      }
      else if (extension == ".vtp")
      {
        vtkSmartPointer<vtkXMLPolyDataReader> reader =
          vtkSmartPointer<vtkXMLPolyDataReader>::New();
        reader->SetFileName (fileName);
        reader->Update();
        polyData = reader->GetOutput();
      }
      else if (extension == ".obj")
      {
        vtkSmartPointer<vtkOBJReader> reader =
          vtkSmartPointer<vtkOBJReader>::New();
        reader->SetFileName (fileName);
        reader->Update();
        polyData = reader->GetOutput();
      }
      else if (extension == ".stl")
      {
        vtkSmartPointer<vtkSTLReader> reader =
          vtkSmartPointer<vtkSTLReader>::New();
        reader->SetFileName (fileName);
        reader->Update();
        polyData = reader->GetOutput();
      }
      else if (extension == ".vtk")
      {
        vtkSmartPointer<vtkPolyDataReader> reader =
          vtkSmartPointer<vtkPolyDataReader>::New();
        reader->SetFileName (fileName);
        reader->Update();
        polyData = reader->GetOutput();
      }
      else if (extension == ".g")
      {
        vtkSmartPointer<vtkBYUReader> reader =
          vtkSmartPointer<vtkBYUReader>::New();
        reader->SetGeometryFileName (fileName);
        reader->Update();
        polyData = reader->GetOutput();
      }
      else
      {
        vtkSmartPointer<vtkSphereSource> source =
          vtkSmartPointer<vtkSphereSource>::New();
        source->SetPhiResolution(25);
        source->SetThetaResolution(25);
        source->Update();
        polyData = source->GetOutput();
      }
      return polyData;
    }
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(BozoShaderDemo)

    find_package(VTK COMPONENTS
      vtkCommonColor
      vtkCommonCore
      vtkCommonTransforms
      vtkFiltersCore
      vtkFiltersGeneral
      vtkFiltersSources
      vtkIOGeometry
      vtkIOLegacy
      vtkIOPLY
      vtkIOXML
      vtkInteractionStyle
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping BozoShaderDemo: ${VTK_NOT_FOUND_MESSAGE}")
      return ()
    endif()
    message (STATUS "VTK_VERSION: ${VTK_VERSION}")
    if (VTK_VERSION VERSION_LESS "8.90.0")
      # old system
      include(${VTK_USE_FILE})
      add_executable(BozoShaderDemo MACOSX_BUNDLE BozoShaderDemo.cxx )
      target_link_libraries(BozoShaderDemo PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(BozoShaderDemo MACOSX_BUNDLE BozoShaderDemo.cxx )
      target_link_libraries(BozoShaderDemo PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS BozoShaderDemo
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build BozoShaderDemo

Click here to download BozoShaderDemo and its CMakeLists.txt file. Once the tarball BozoShaderDemo.tar has been downloaded and extracted,

    cd BozoShaderDemo/build

If VTK is installed:

    cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

    cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

Build the project:

    make

and run it:

    ./BozoShaderDemo

WINDOWS USERS

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.