SpatterShader

#include <vtkSmartPointer.h>

#include <vtkCamera.h>
#include <vtkRenderer.h>
#include <vtkRenderWindow.h>
#include <vtkShaderProgram.h>
#include <vtkActor.h>
#include <vtkOpenGLPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkTransform.h>
#include <vtkTransformPolyDataFilter.h>
#include <vtkPolyDataNormals.h>
#include <vtkTriangleFilter.h>
#include <vtkCleanPolyData.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 uniform variables in the shader for each render. We do this with a
// callback for the UpdateShaderEvent
class ShaderCallback : public vtkCommand
{
public:
  static ShaderCallback *New()
    { return new ShaderCallback; }
  vtkRenderer *Renderer;
  float specksize;
  int sizes;
  float basecolor[3];
  float spattercolor[3];

  void Execute(vtkObject *, unsigned long, void* calldata) override
  {
    vtkShaderProgram *program = reinterpret_cast<vtkShaderProgram*>(calldata);
    if (program)
    {
      program->SetUniformf("specksize", specksize);
      program->SetUniformi("sizes", sizes);
      program->SetUniform3f("basecolor", basecolor);
      program->SetUniform3f("spattercolor", spattercolor);
    }
  }

  void Print(std::ostream &os)
  {
    os << "specksize: " << specksize << std::endl;
    os << "sizes: " << sizes << std::endl;
    os << "basecolor: "
       << basecolor[0] << ", "
       << basecolor[1] << ", "
       << basecolor[2] << std::endl;
    os << "spattercolor: "
       << spattercolor[0] << ", "
       << spattercolor[1] << ", "
       << spattercolor[2] << std::endl;
  }

  ShaderCallback()
  {
    this->Renderer = nullptr;
    // size of the smallest paint specks
    this->specksize = .05;
    // number of different sizes of paint specks (each doubles the previous size)   
    this->sizes = 3;
    // the background color on which to spatter paint
    this->basecolor[0] = this->basecolor[1] = this->basecolor[2]  = .7;
    //  the color of the paint spatters
    this->spattercolor[0] = this->spattercolor[1] = this->spattercolor[2]  = 0.0;
  }
};
}
namespace
{
vtkSmartPointer<vtkPolyData> ReadPolyData(const char *fileName);
}

//----------------------------------------------------------------------------
int main(int argc, char *argv[])
{
  if (argc < 2)
  {
    std::cout << "Usage: " << argv[0] << " PerlnNoise.glsl "
              << "[polydataFile] "
              << "[specksize(.05)] "
              << "[sizes(3)] "
              << "[basecolor{.7,.7,.7)] "
              << "[spattercolor(0.0,0.0,0.0)] "
              << std::endl;
    return EXIT_FAILURE;
  }

  vtkSmartPointer<vtkPolyData> polyData =
    ReadPolyData(argc > 2 ? argv[2] : "");

  std::ifstream shaderFile(argv[1]);
  std::ostringstream shaderCode;
  shaderCode << shaderFile.rdbuf();

// 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]);

  vtkSmartPointer<vtkNamedColors> colors =
    vtkSmartPointer<vtkNamedColors>::New();

  vtkSmartPointer<vtkActor> actor =
    vtkSmartPointer<vtkActor>::New();

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

  vtkSmartPointer<vtkRenderWindow> renderWindow =
    vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->SetSize(640, 480);
  renderWindow->AddRenderer(renderer);
  renderer->AddActor(actor);

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

  // Clean
  vtkSmartPointer<vtkCleanPolyData> clean =
    vtkSmartPointer<vtkCleanPolyData>::New();
  clean->SetInputData(polyData);
  // 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->SetInputConnection(clean->GetOutputPort());

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

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

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

  actor->SetMapper(mapper);
  actor->GetProperty()->SetDiffuse(1.0);
  actor->GetProperty()->SetDiffuseColor(colors->GetColor3d("ivoryblack").GetData());
  actor->GetProperty()->SetSpecular(.5);
  actor->GetProperty()->SetSpecularPower(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 specksize = .05;\n"
    "uniform int sizes = 3;\n"
    "uniform vec3 basecolor = vec3(.7,.7,.7);\n"
    "uniform vec3 spattercolor = vec3(0.0, 0.0, 0.0);\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"
    "\n"
    "float speckle, size, threshold = 0.7;\n"
    "vec3 paint;\n"
    "float scalefac;\n"
    "vec4 myLocalVertexMC = myVertexMC;\n"
    "scalefac = 1.0/specksize;\n"
    "paint = basecolor;\n"
    "for (size=1; size<=sizes; size +=1) {\n"
    "  speckle = pnoise(myLocalVertexMC * scalefac);\n"
    "  if (speckle > threshold) {\n"
    "    paint = spattercolor;\n"
    "    break;\n"
    "  }\n"
    "  scalefac /= 2.0;\n"
    "}\n"
    "/* get final color */\n"
    "fragOutput0.rgb = opacity * vec3(ambientColor + paint + specular);\n"
    "fragOutput0.a = opacity;\n"    
    ,
    false // only do once
    );

  vtkSmartPointer<ShaderCallback> myCallback =
    vtkSmartPointer<ShaderCallback>::New();
  myCallback->Renderer = renderer;
  if (argc == 4)
  {
    myCallback->specksize = atof(argv[3]);
  }
  if (argc == 5)
  {
    myCallback->specksize = atof(argv[3]);
    myCallback->sizes = atoi(argv[4]);
  }
  if (argc == 8)
  {
    myCallback->specksize = atof(argv[3]);
    myCallback->sizes = atoi(argv[4]);
    myCallback->basecolor[0] = atof(argv[5]);
    myCallback->basecolor[1] = atof(argv[6]);
    myCallback->basecolor[2] = atof(argv[7]);
  }
  if (argc == 11)
  {
    myCallback->specksize = atof(argv[3]);
    myCallback->sizes = atoi(argv[4]);
    myCallback->basecolor[0] = atof(argv[5]);
    myCallback->basecolor[1] = atof(argv[6]);
    myCallback->basecolor[2] = atof(argv[7]);
    myCallback->spattercolor[0] = atof(argv[8]);
    myCallback->spattercolor[1] = atof(argv[9]);
    myCallback->spattercolor[2] = atof(argv[10]);
  }
  std::cout << "Input: " << (argc > 2 ? argv[2] : "Generated Sphere") << std::endl;
  myCallback->Print(std::cout);
  mapper->AddObserver(vtkCommand::UpdateShaderEvent, myCallback);

  renderWindow->Render();
  renderer->GetActiveCamera()->SetPosition(-.3, 0, .08);
  renderer->GetActiveCamera()->SetFocalPoint(0,0,0);
  renderer->GetActiveCamera()->SetViewUp(.26, 0.0, .96);
  renderer->ResetCamera();
  renderer->GetActiveCamera()->Zoom(1.5);
  renderWindow->Render();
  interactor->Start();

  transform->GetOutput()->GetBounds(bounds);
  std::cout << "Range: "
            << " x " << bounds[1] - bounds[0]
            << " y " << bounds[3] - bounds[2]
            << " y " << bounds[5] - bounds[4]
            << std::endl;
  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;
}
}

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(SpatterShader)

find_package(VTK COMPONENTS 
  vtkCommonColor
  vtkCommonCore
  vtkCommonTransforms
  vtkFiltersCore
  vtkFiltersGeneral
  vtkFiltersSources
  vtkIOGeometry
  vtkIOLegacy
  vtkIOPLY
  vtkIOXML
  vtkInteractionStyle
  vtkRenderingContextOpenGL2
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingGL2PSOpenGL2
  vtkRenderingOpenGL2 QUIET)
if (NOT VTK_FOUND)
  message("Skipping SpatterShader: ${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(SpatterShader MACOSX_BUNDLE SpatterShader.cxx )
  target_link_libraries(SpatterShader PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(SpatterShader MACOSX_BUNDLE SpatterShader.cxx )
  target_link_libraries(SpatterShader PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS SpatterShader
    MODULES ${VTK_LIBRARIES}
    )
endif () 

cd SpatterShader/build 

cmake ..

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

make

./SpatterShader