/*=========================================================================

  Program:   Visualization Toolkit
  Module:    vtkCompositeZPass.cxx

  Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
  All rights reserved.
  See Copyright.txt or http://www.kitware.com/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notice for more information.

=========================================================================*/

#include "vtkCompositeZPass.h"
#include "vtkObjectFactory.h"
#include "vtkOpenGLRenderWindow.h"
#include "vtkOpenGLRenderer.h"
#include "vtkOpenGLState.h"
#include "vtkRenderState.h"
#include "vtkTextureObject.h"
#include <cassert>

// to be able to dump intermediate result into png files for debugging.
// only for vtkCompositeZPass developers.
//#define VTK_COMPOSITE_ZPASS_DEBUG

#include "vtkFrameBufferObjectBase.h"
#include "vtkImageData.h"
#include "vtkImageExtractComponents.h"
#include "vtkImageImport.h"
#include "vtkImageShiftScale.h"
#include "vtkMultiProcessController.h"
#include "vtkPNGWriter.h"
#include "vtkPixelBufferObject.h"
#include "vtkPointData.h"
#include "vtkStdString.h"
#include "vtkTimerLog.h"
#include <sstream>

#ifdef VTK_COMPOSITE_ZPASS_DEBUG
//#include <unistd.h>
#include <sys/syscall.h>
#include <sys/types.h> // Linux specific gettid()
#endif

#include "vtkCompositeZPassFS.h"
#include "vtkOpenGLHelper.h"
#include "vtkOpenGLShaderCache.h"
#include "vtkShaderProgram.h"
#include "vtkTextureObjectVS.h"
#include "vtk_glew.h"

vtkStandardNewMacro(vtkCompositeZPass);
vtkCxxSetObjectMacro(vtkCompositeZPass, Controller, vtkMultiProcessController);

//------------------------------------------------------------------------------
vtkCompositeZPass::vtkCompositeZPass()
{
  this->Controller = nullptr;
  this->PBO = nullptr;
  this->ZTexture = nullptr;
  this->Program = nullptr;
  this->RawZBuffer = nullptr;
  this->RawZBufferSize = 0;
}

//------------------------------------------------------------------------------
vtkCompositeZPass::~vtkCompositeZPass()
{
  if (this->Controller != nullptr)
  {
    this->Controller->Delete();
  }
  if (this->PBO != nullptr)
  {
    vtkErrorMacro(<< "PixelBufferObject should have been deleted in ReleaseGraphicsResources().");
  }
  if (this->ZTexture != nullptr)
  {
    vtkErrorMacro(<< "ZTexture should have been deleted in ReleaseGraphicsResources().");
  }
  if (this->Program != nullptr)
  {
    delete this->Program;
    this->Program = nullptr;
  }
  delete[] this->RawZBuffer;
}

//------------------------------------------------------------------------------
void vtkCompositeZPass::PrintSelf(ostream& os, vtkIndent indent)
{
  this->Superclass::PrintSelf(os, indent);

  os << indent << "Controller:";
  if (this->Controller != nullptr)
  {
    this->Controller->PrintSelf(os, indent);
  }
  else
  {
    os << "(none)" << endl;
  }
}

//------------------------------------------------------------------------------
bool vtkCompositeZPass::IsSupported(vtkOpenGLRenderWindow* context)
{
  return context != nullptr;
}

//------------------------------------------------------------------------------
// Description:
// Perform rendering according to a render state \p s.
// \pre s_exists: s!=0
void vtkCompositeZPass::Render(const vtkRenderState* s)
{
  assert("pre: s_exists" && s != nullptr);

  if (this->Controller == nullptr)
  {
    vtkErrorMacro(<< " no controller.");
    return;
  }

  int numProcs = this->Controller->GetNumberOfProcesses();

  if (numProcs == 1)
  {
    return; // nothing to do.
  }

  int me = this->Controller->GetLocalProcessId();

  const int VTK_COMPOSITE_Z_PASS_MESSAGE_GATHER = 101;
  const int VTK_COMPOSITE_Z_PASS_MESSAGE_SCATTER = 102;

  vtkOpenGLRenderer* r = static_cast<vtkOpenGLRenderer*>(s->GetRenderer());
  vtkOpenGLRenderWindow* context = static_cast<vtkOpenGLRenderWindow*>(r->GetRenderWindow());
  vtkOpenGLState* ostate = context->GetState();

  int w = 0;
  int h = 0;

  vtkFrameBufferObjectBase* fbo = s->GetFrameBuffer();
  if (fbo == nullptr)
  {
    r->GetTiledSize(&w, &h);
  }
  else
  {
    int size[2];
    fbo->GetLastSize(size);
    w = size[0];
    h = size[1];
  }

  unsigned int numTups = static_cast<unsigned int>(w * h);

  // pbo arguments.
  unsigned int dims[2];
  vtkIdType continuousInc[3];

  dims[0] = static_cast<unsigned int>(w);
  dims[1] = static_cast<unsigned int>(h);
  continuousInc[0] = 0;
  continuousInc[1] = 0;
  continuousInc[2] = 0;

  if (this->RawZBufferSize < static_cast<size_t>(w * h))
  {
    delete[] this->RawZBuffer;
  }
  if (this->RawZBuffer == nullptr)
  {
    this->RawZBufferSize = static_cast<size_t>(w * h);
    this->RawZBuffer = new float[this->RawZBufferSize];
  }

  if (this->PBO == nullptr)
  {
    this->PBO = vtkPixelBufferObject::New();
    this->PBO->SetContext(context);
  }
  if (this->ZTexture == nullptr)
  {
    this->ZTexture = vtkTextureObject::New();
    this->ZTexture->SetContext(context);
  }

  // TO: texture object
  // PBO: pixel buffer object
  // FB: framebuffer

#ifdef VTK_COMPOSITE_ZPASS_DEBUG
  vtkTimerLog* timer = vtkTimerLog::New();

  vtkImageImport* importer;
  vtkImageShiftScale* converter;
  vtkPNGWriter* writer;

  cout << "me=" << me << " TID=" << syscall(SYS_gettid) << " thread=" << pthread_self() << endl;
  timer->StartTimer();
#endif

  if (me == 0)
  {
    // root
    // 1. for each satellite
    // 1.a   receive zbuffer
    // 1.b   composite z against zbuffer in framebuffer
    // 2. send final zbuffer of the framebuffer to all satellites

#ifdef VTK_COMPOSITE_ZPASS_DEBUG

    // get z-buffer of root before any blending with satellite
    // for debugging only.

    // Framebuffer to PBO
    this->PBO->Allocate(VTK_FLOAT, numTups, 1, vtkPixelBufferObject::PACKED_BUFFER);

    this->PBO->Bind(vtkPixelBufferObject::PACKED_BUFFER);
    glReadPixels(0, 0, w, h, GL_DEPTH_COMPONENT, GL_FLOAT, static_cast<GLfloat*>(nullptr));

    state->Update();
    vtkIndent indent;
    std::ostringstream ost00;
    ost00.setf(ios::fixed, ios::floatfield);
    ost00.precision(5);
    ost00 << "OpenGLState_" << pthread_self() << "_" << vtkTimerLog::GetUniversalTime()
          << "_root00.txt";
    vtksys::ofstream outfile00(ost00.str().c_str());
    state->PrintSelf(outfile00, indent);
    outfile00.close();

    this->PBO->Download2D(VTK_FLOAT, this->RawZBuffer, dims, 1, continuousInc);

    state->Update();
    std::ostringstream ost01;
    ost01.setf(ios::fixed, ios::floatfield);
    ost01.precision(5);
    ost01 << "OpenGLState_" << pthread_self() << "_" << vtkTimerLog::GetUniversalTime()
          << "_root01.txt";
    vtksys::ofstream outfile01(ost01.str().c_str());
    state->PrintSelf(outfile01, indent);
    outfile01.close();

    importer = vtkImageImport::New();
    importer->CopyImportVoidPointer(this->RawZBuffer, static_cast<int>(byteSize));
    importer->SetDataScalarTypeToFloat();
    importer->SetNumberOfScalarComponents(1);
    importer->SetWholeExtent(0, w - 1, 0, h - 1, 0, 0);
    importer->SetDataExtentToWholeExtent();

    importer->Update();
    double range[2];
    importer->GetOutput()->GetPointData()->GetScalars()->GetRange(range);

    cout << "root0 scalar range=" << range[0] << "," << range[1] << endl;

    converter = vtkImageShiftScale::New();
    converter->SetInputConnection(importer->GetOutputPort());
    converter->SetOutputScalarTypeToUnsignedChar();
    converter->SetShift(0.0);
    converter->SetScale(255.0);

    //      vtkImageExtractComponents *rgbaToRgb=vtkImageExtractComponents::New();
    //    rgbaToRgb->SetInputConnection(importer->GetOutputPort());
    //    rgbaToRgb->SetComponents(0,1,2);

    std::ostringstream ostxx;
    ostxx.setf(ios::fixed, ios::floatfield);
    ostxx.precision(5);
    timer->StopTimer();
    ostxx << "root0_" << vtkTimerLog::GetUniversalTime() << "_.png";

    vtkStdString* sssxx = new vtkStdString;
    (*sssxx) = ostxx.str();

    writer = vtkPNGWriter::New();
    writer->SetFileName(*sssxx);
    delete sssxx;
    writer->SetInputConnection(converter->GetOutputPort());
    importer->Delete();
    //    rgbaToRgb->Delete();
    cout << "Writing " << writer->GetFileName() << endl;
    writer->Write();
    cout << "Wrote " << writer->GetFileName() << endl;
    //    sleep(30);
    writer->Delete();

#endif // #ifdef VTK_COMPOSITE_ZPASS_DEBUG

    int proc = 1;
    while (proc < numProcs)
    {
      // receive the zbuffer from satellite process.
      this->Controller->Receive(this->RawZBuffer, static_cast<vtkIdType>(this->RawZBufferSize),
        proc, VTK_COMPOSITE_Z_PASS_MESSAGE_GATHER);

#ifdef VTK_COMPOSITE_ZPASS_DEBUG
      importer = vtkImageImport::New();
      importer->CopyImportVoidPointer(this->RawZBuffer, static_cast<int>(byteSize));
      importer->SetDataScalarTypeToFloat();
      importer->SetNumberOfScalarComponents(1);
      importer->SetWholeExtent(0, w - 1, 0, h - 1, 0, 0);
      importer->SetDataExtentToWholeExtent();

      converter = vtkImageShiftScale::New();
      converter->SetInputConnection(importer->GetOutputPort());
      converter->SetOutputScalarTypeToUnsignedChar();
      converter->SetShift(0.0);
      converter->SetScale(255.0);

      //      vtkImageExtractComponents *rgbaToRgb=vtkImageExtractComponents::New();
      //    rgbaToRgb->SetInputConnection(importer->GetOutputPort());
      //    rgbaToRgb->SetComponents(0,1,2);

      writer = vtkPNGWriter::New();
      std::ostringstream ost;
      timer->StopTimer();
      ost.setf(ios::fixed, ios::floatfield);
      ost.precision(5);
      ost << "root1_proc_" << proc << "_" << vtkTimerLog::GetUniversalTime() << "_.png";

      vtkStdString* sss = new vtkStdString;
      (*sss) = ost.str();

      writer->SetFileName(*sss);
      delete sss;
      writer->SetInputConnection(converter->GetOutputPort());
      importer->Delete();
      //    rgbaToRgb->Delete();
      cout << "Writing " << writer->GetFileName() << endl;
      writer->Write();
      cout << "Wrote " << writer->GetFileName() << endl;
      //    sleep(30);
      writer->Delete();
#endif

      // send it to a PBO
      ostate->vtkglPixelStorei(GL_UNPACK_ALIGNMENT, 1); // client to server

#ifdef VTK_COMPOSITE_ZPASS_DEBUG
      state->Update();
      std::ostringstream ost02;
      ost02.setf(ios::fixed, ios::floatfield);
      ost02.precision(5);
      ost02 << "OpenGLState_" << pthread_self() << "_" << vtkTimerLog::GetUniversalTime()
            << "_root02_proc_" << proc << "_"
            << ".txt";
      vtksys::ofstream outfile02(ost02.str().c_str());
      state->PrintSelf(outfile02, indent);
      outfile02.close();
#endif

      this->PBO->Upload2D(VTK_FLOAT, this->RawZBuffer, dims, 1, continuousInc);

#ifdef VTK_COMPOSITE_ZPASS_DEBUG
      state->Update();
      std::ostringstream ost03;
      ost03.setf(ios::fixed, ios::floatfield);
      ost03.precision(5);
      ost03 << "OpenGLState_" << pthread_self() << "_" << vtkTimerLog::GetUniversalTime()
            << "_root03_proc_" << proc << "_"
            << ".txt";
      vtksys::ofstream outfile03(ost03.str().c_str());
      state->PrintSelf(outfile03, indent);
      outfile03.close();

      GLint value;
      glGetIntegerv(vtkgl::PIXEL_UNPACK_BUFFER_BINDING, &value);
      cout << pthread_self() << "compz pixel unpack buffer=" << value << endl;
      glGetIntegerv(vtkgl::PIXEL_PACK_BUFFER_BINDING, &value);
      cout << pthread_self() << "compz pixel unpack buffer=" << value << endl;
#endif

      // Send PBO to TO
      this->ZTexture->CreateDepth(dims[0], dims[1], vtkTextureObject::Native, this->PBO);

      if (this->Program == nullptr)
      {
        this->CreateProgram(context);
      }

#ifdef VTK_COMPOSITE_ZPASS_DEBUG
      cout << "sourceId=" << sourceId << endl;
#endif

      // Apply TO on quad with special zcomposite fragment shader.
      ostate->vtkglColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
      ostate->vtkglEnable(GL_DEPTH_TEST);
      ostate->vtkglDepthMask(GL_TRUE);
      ostate->vtkglDepthFunc(GL_LEQUAL);

      context->GetShaderCache()->ReadyShaderProgram(this->Program->Program);
      this->ZTexture->Activate();
      this->Program->Program->SetUniformi("depth", this->ZTexture->GetTextureUnit());

#ifdef VTK_COMPOSITE_ZPASS_DEBUG
      state->Update();
      std::ostringstream ost04;
      ost04.setf(ios::fixed, ios::floatfield);
      ost04.precision(5);
      ost04 << "OpenGLState_" << pthread_self() << "_" << vtkTimerLog::GetUniversalTime()
            << "_root_proc_" << proc << "_before_copyframe.txt";
      vtksys::ofstream outfile04(ost04.str().c_str());
      state->PrintSelf(outfile04, indent);
      outfile04.close();
#endif

      this->ZTexture->CopyToFrameBuffer(
        0, 0, w - 1, h - 1, 0, 0, w, h, this->Program->Program, this->Program->VAO);

#ifdef VTK_COMPOSITE_ZPASS_DEBUG
      state->Update();
      std::ostringstream ost05;
      ost05.setf(ios::fixed, ios::floatfield);
      ost05.precision(5);
      ost05 << "OpenGLState_" << pthread_self() << "_" << vtkTimerLog::GetUniversalTime()
            << "_root_proc_" << proc << "_after_copyframe.txt";
      vtksys::ofstream outfile05(ost05.str().c_str());
      state->PrintSelf(outfile05, indent);
      outfile05.close();
#endif

      this->ZTexture->Deactivate();

#ifdef VTK_COMPOSITE_ZPASS_DEBUG
      state->Update();
      std::ostringstream ost06;
      ost06.setf(ios::fixed, ios::floatfield);
      ost06.precision(5);
      ost06 << "OpenGLState_" << pthread_self() << "_" << vtkTimerLog::GetUniversalTime()
            << "_root_proc_" << proc << "_before_popattrib.txt";
      vtksys::ofstream outfile06(ost06.str().c_str());
      state->PrintSelf(outfile06, indent);
      outfile06.close();
#endif

#ifdef VTK_COMPOSITE_ZPASS_DEBUG
      state->Update();
      std::ostringstream ost07;
      ost07.setf(ios::fixed, ios::floatfield);
      ost07.precision(5);
      ost07 << "OpenGLState_" << pthread_self() << "_" << vtkTimerLog::GetUniversalTime()
            << "_root_proc_" << proc << "_after_popattrib.txt";
      vtksys::ofstream outfile07(ost07.str().c_str());
      state->PrintSelf(outfile07, indent);
      outfile07.close();
#endif

      ++proc;
    }

    // Send the final z-buffer from the framebuffer to a PBO
    // TODO

    this->PBO->Allocate(VTK_FLOAT, numTups, 1, vtkPixelBufferObject::PACKED_BUFFER);

    this->PBO->Bind(vtkPixelBufferObject::PACKED_BUFFER);
    glReadPixels(0, 0, w, h, GL_DEPTH_COMPONENT, GL_FLOAT, static_cast<GLfloat*>(nullptr));

    // PBO to client
    this->PBO->Download2D(VTK_FLOAT, this->RawZBuffer, dims, 1, continuousInc);

#ifdef VTK_COMPOSITE_ZPASS_DEBUG
    importer = vtkImageImport::New();
    importer->CopyImportVoidPointer(this->RawZBuffer, static_cast<int>(byteSize));
    importer->SetDataScalarTypeToFloat();
    importer->SetNumberOfScalarComponents(1);
    importer->SetWholeExtent(0, w - 1, 0, h - 1, 0, 0);
    importer->SetDataExtentToWholeExtent();

    converter = vtkImageShiftScale::New();
    converter->SetInputConnection(importer->GetOutputPort());
    converter->SetOutputScalarTypeToUnsignedChar();
    converter->SetShift(0.0);
    converter->SetScale(255.0);

    //      vtkImageExtractComponents *rgbaToRgb=vtkImageExtractComponents::New();
    //    rgbaToRgb->SetInputConnection(importer->GetOutputPort());
    //    rgbaToRgb->SetComponents(0,1,2);

    std::ostringstream ost3;
    ost3.setf(ios::fixed, ios::floatfield);
    ost3.precision(5);

    ost3 << "root2_" << vtkTimerLog::GetUniversalTime() << "_.png";

    vtkStdString* sss3 = new vtkStdString;
    (*sss3) = ost3.str();

    writer = vtkPNGWriter::New();
    writer->SetFileName(*sss3);
    delete sss3;
    writer->SetInputConnection(converter->GetOutputPort());
    importer->Delete();
    //    rgbaToRgb->Delete();
    cout << "Writing " << writer->GetFileName() << endl;
    writer->Write();
    cout << "Wrote " << writer->GetFileName() << endl;
    writer->Delete();
#endif

    // Send the c-array to all satellites
    proc = 1;
    while (proc < numProcs)
    {
      this->Controller->Send(this->RawZBuffer, static_cast<vtkIdType>(this->RawZBufferSize), proc,
        VTK_COMPOSITE_Z_PASS_MESSAGE_SCATTER);
      ++proc;
    }
  }
  else
  {
    // satellite
    // 1. send z-buffer
    // 2. receive final z-buffer and copy it

    // framebuffer to PBO.
    this->PBO->Allocate(VTK_FLOAT, numTups, 1, vtkPixelBufferObject::PACKED_BUFFER);

    this->PBO->Bind(vtkPixelBufferObject::PACKED_BUFFER);
    glReadPixels(0, 0, w, h, GL_DEPTH_COMPONENT, GL_FLOAT, static_cast<GLfloat*>(nullptr));

    // PBO to client
    this->PBO->Download2D(VTK_FLOAT, this->RawZBuffer, dims, 1, continuousInc);

#ifdef VTK_COMPOSITE_ZPASS_DEBUG
    importer = vtkImageImport::New();
    importer->CopyImportVoidPointer(this->RawZBuffer, static_cast<int>(byteSize));
    importer->SetDataScalarTypeToFloat();
    importer->SetNumberOfScalarComponents(1);
    importer->SetWholeExtent(0, w - 1, 0, h - 1, 0, 0);
    importer->SetDataExtentToWholeExtent();

    importer->Update();
    double range[2];
    importer->GetOutput()->GetPointData()->GetScalars()->GetRange(range);

    cout << " scalar range=" << range[0] << "," << range[1] << endl;

    converter = vtkImageShiftScale::New();
    converter->SetInputConnection(importer->GetOutputPort());
    converter->SetOutputScalarTypeToUnsignedChar();
    converter->SetShift(0.0);
    converter->SetScale(255.0);

    //      vtkImageExtractComponents *rgbaToRgb=vtkImageExtractComponents::New();
    //    rgbaToRgb->SetInputConnection(importer->GetOutputPort());
    //    rgbaToRgb->SetComponents(0,1,2);

    std::ostringstream ost;
    ost.setf(ios::fixed, ios::floatfield);
    ost.precision(5);
    timer->StopTimer();
    ost << "satellite1_" << vtkTimerLog::GetUniversalTime() << "_.png";

    vtkStdString* sss = new vtkStdString;
    (*sss) = ost.str();

    writer = vtkPNGWriter::New();
    writer->SetFileName(*sss);
    delete sss;
    writer->SetInputConnection(converter->GetOutputPort());
    importer->Delete();
    //    rgbaToRgb->Delete();
    cout << "Writing " << writer->GetFileName() << endl;
    writer->Write();
    cout << "Wrote " << writer->GetFileName() << endl;
    //    sleep(30);
    writer->Delete();
#endif

    // client to root process
    this->Controller->Send(this->RawZBuffer, static_cast<vtkIdType>(this->RawZBufferSize), 0,
      VTK_COMPOSITE_Z_PASS_MESSAGE_GATHER);

    // receiving final z-buffer.
    this->Controller->Receive(this->RawZBuffer, static_cast<vtkIdType>(this->RawZBufferSize), 0,
      VTK_COMPOSITE_Z_PASS_MESSAGE_SCATTER);

#ifdef VTK_COMPOSITE_ZPASS_DEBUG
    importer = vtkImageImport::New();
    importer->CopyImportVoidPointer(this->RawZBuffer, static_cast<int>(byteSize));
    importer->SetDataScalarTypeToFloat();
    importer->SetNumberOfScalarComponents(1);
    importer->SetWholeExtent(0, w - 1, 0, h - 1, 0, 0);
    importer->SetDataExtentToWholeExtent();

    converter = vtkImageShiftScale::New();
    converter->SetInputConnection(importer->GetOutputPort());
    converter->SetOutputScalarTypeToUnsignedChar();
    converter->SetShift(0.0);
    converter->SetScale(255.0);
    //      vtkImageExtractComponents *rgbaToRgb=vtkImageExtractComponents::New();
    //    rgbaToRgb->SetInputConnection(importer->GetOutputPort());
    //    rgbaToRgb->SetComponents(0,1,2);

    std::ostringstream ost2;
    ost2.setf(ios::fixed, ios::floatfield);
    ost2.precision(5);
    timer->StopTimer();

    ost2 << "satellite2_" << vtkTimerLog::GetUniversalTime() << "_.png";

    vtkStdString* sss2 = new vtkStdString;
    (*sss2) = ost2.str();

    writer = vtkPNGWriter::New();
    writer->SetFileName(*sss2);
    delete sss2;
    writer->SetInputConnection(converter->GetOutputPort());
    importer->Delete();
    //    rgbaToRgb->Delete();
    cout << "Writing " << writer->GetFileName() << endl;
    writer->Write();
    cout << "Wrote " << writer->GetFileName() << endl;
    writer->Delete();
#endif

    // client to PBO
    this->PBO->Upload2D(VTK_FLOAT, this->RawZBuffer, dims, 1, continuousInc);

    // PBO to TO
    this->ZTexture->CreateDepth(dims[0], dims[1], vtkTextureObject::Native, this->PBO);

    // TO to FB: apply TO on quad with special zcomposite fragment shader.
    ostate->vtkglColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
    ostate->vtkglEnable(GL_DEPTH_TEST);
    ostate->vtkglDepthMask(GL_TRUE);
    ostate->vtkglDepthFunc(GL_ALWAYS);

    if (this->Program == nullptr)
    {
      this->CreateProgram(context);
    }

    context->GetShaderCache()->ReadyShaderProgram(this->Program->Program);
    this->ZTexture->Activate();
    this->Program->Program->SetUniformi("depth", this->ZTexture->GetTextureUnit());
    this->ZTexture->CopyToFrameBuffer(
      0, 0, w - 1, h - 1, 0, 0, w, h, this->Program->Program, this->Program->VAO);
    this->ZTexture->Deactivate();
  }
#ifdef VTK_COMPOSITE_ZPASS_DEBUG
  delete state;
  timer->Delete();
#endif
}

//------------------------------------------------------------------------------
void vtkCompositeZPass::CreateProgram(vtkOpenGLRenderWindow* context)
{
  assert("pre: context_exists" && context != nullptr);
  assert("pre: Program_void" && this->Program == nullptr);

  this->Program = new vtkOpenGLHelper;
  this->Program->Program =
    context->GetShaderCache()->ReadyShaderProgram(vtkTextureObjectVS, vtkCompositeZPassFS, "");
  if (!this->Program->Program)
  {
    vtkErrorMacro("Shader program failed to build.");
  }

  assert("post: Program_exists" && this->Program != nullptr);
}

//------------------------------------------------------------------------------
// Description:
// Release graphics resources and ask components to release their own
// resources.
// \pre w_exists: w!=0
void vtkCompositeZPass::ReleaseGraphicsResources(vtkWindow* w)
{
  assert("pre: w_exists" && w != nullptr);

  (void)w;

  if (this->PBO != nullptr)
  {
    this->PBO->Delete();
    this->PBO = nullptr;
  }
  if (this->ZTexture != nullptr)
  {
    this->ZTexture->Delete();
    this->ZTexture = nullptr;
  }
  if (this->Program != nullptr)
  {
    this->Program->ReleaseGraphicsResources(w);
  }
}