VTK学习笔记（二十）VTK组织透镜

组织透镜效果，可以适当看下被遮挡的地方究竟是什么样子的，比单独看切片要好一些，当然实际效果还需要综合考量。

此示例使用两个vtkClipDataSet过滤器来实现“组织透镜”效果。首先，使用vtkSphere隐式函数在用vtkFlyingEdges3D或vtkMarchingCubes提取的等值面中剪裁球面孔。然后是几何[vtkSphere](VTK: vtkSphere Class Reference）Source使用vtkProbeFilter对原始卷数据进行采样。vtkClipDataSet使用生成的标量点数据来剪裁具有等值面的球面。

具体看代码

#include 
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#include 
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#include 
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#include 
#include 
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#include 
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#include 
#include 
//#include 
//GPUVolumeRenderMapper
#include 

// vtkFlyingEdges3D was introduced in VTK >= 8.2
#if VTK_MAJOR_VERSION >= 9 || (VTK_MAJOR_VERSION >= 8 && VTK_MINOR_VERSION >= 2)
#define USE_FLYING_EDGES
#else
#undef USE_FLYING_EDGES
#endif

#ifdef USE_FLYING_EDGES
#include 
#else
#include 
#endif

#include 
#include 
VTK_MODULE_INIT(vtkRenderingOpenGL2);
VTK_MODULE_INIT(vtkInteractionStyle);
VTK_MODULE_INIT(vtkRenderingContextOpenGL2);
VTK_MODULE_INIT(vtkRenderingVolumeOpenGL2);  //新的

int main(int argc, char* argv[])
{
  vtkNew colors;

  std::array skinColor{{240, 184, 160, 255}};
  colors->SetColor("SkinColor", skinColor.data());
  std::array backColor{{255, 229, 200, 255}};
  colors->SetColor("BackfaceColor", backColor.data());
  std::array bkg{{51, 77, 102, 255}};
  colors->SetColor("BkgColor", bkg.data());

  if (argc < 2)
  {
    cout << "Usage: " << argv[0] << " file.mhd e.g. FullHead.mhd" << endl;
    return EXIT_FAILURE;
  }

  // 读取体数据
  vtkNew reader;
  reader->SetFileName(argv[1]);
  reader->Update();

  //已知对应于患者的皮肤，数值是500的等值面或轮廓值。 
#ifdef USE_FLYING_EDGES
  vtkNew skinExtractor;
#else
  vtkNew skinExtractor;
#endif
  skinExtractor->SetInputConnection(reader->GetOutputPort());
  skinExtractor->SetValue(0, 500);  //500

  //定义一个球形剪裁函数来剪裁等值面
  vtkNew clipFunction;
  clipFunction->SetRadius(50);
  clipFunction->SetCenter(73, 52, 15);

  //用球体剪裁等值面
  vtkNew skinClip;
  skinClip->SetInputConnection(skinExtractor->GetOutputPort());
  skinClip->SetClipFunction(clipFunction);
  skinClip->SetValue(0);
  skinClip->GenerateClipScalarsOn();
  skinClip->Update();

  vtkNew skinMapper;
  skinMapper->SetInputConnection(skinClip->GetOutputPort());
  skinMapper->ScalarVisibilityOff();

  vtkNew skin;
  skin->SetMapper(skinMapper);
  skin->GetProperty()->SetDiffuseColor(
      colors->GetColor3d("SkinColor").GetData());

  vtkNew backProp;
  backProp->SetDiffuseColor(colors->GetColor3d("BackfaceColor").GetData());
  skin->SetBackfaceProperty(backProp);

  //为“镜头”定义一个模型。其几何图形与用于剪裁等值面的隐式球体相匹配 
  vtkNew lensModel;
  lensModel->SetRadius(50);
  lensModel->SetCenter(73, 52, 15);
  lensModel->SetPhiResolution(201);
  lensModel->SetThetaResolution(101);

  // 使用透镜模型几何结构对输入体数据进行采样
  vtkNew lensProbe;
  lensProbe->SetInputConnection(lensModel->GetOutputPort());
  lensProbe->SetSourceConnection(reader->GetOutputPort());

  // 使用等值面值剪裁镜头数据
  vtkNew lensClip;
  lensClip->SetInputConnection(lensProbe->GetOutputPort());
  lensClip->SetValue(500);
  lensClip->GenerateClipScalarsOff();
  lensClip->Update();

  // 定义合适的灰度lut表
  vtkNew bwLut;
  bwLut->SetTableRange(0, 2048);
  bwLut->SetSaturationRange(0, 0);
  bwLut->SetHueRange(0, 0);
  bwLut->SetValueRange(0.2, 1);
  bwLut->Build();

  vtkNew lensMapper;
  lensMapper->SetInputConnection(lensClip->GetOutputPort());
  lensMapper->SetScalarRange(lensClip->GetOutput()->GetScalarRange());
  lensMapper->SetLookupTable(bwLut);

  vtkNew lens;
  lens->SetMapper(lensMapper);

  // 创建数据的初始视图很方便。FocalPoint和Position形成一个矢量方向。稍后（ResetCamera方法），此向量用于定位相机，以查看此方向上的数据。
  vtkNew aCamera;
  aCamera->SetViewUp(0, 0, -1);
  aCamera->SetPosition(0, -1, 0);
  aCamera->SetFocalPoint(0, 0, 0);
  aCamera->ComputeViewPlaneNormal();
  aCamera->Azimuth(30.0);
  aCamera->Elevation(30.0);

  创建渲染器、渲染窗口和交互器等
  vtkNew aRenderer;
  vtkNew renWin;
  renWin->AddRenderer(aRenderer);
  vtkNew iren;
  iren->SetRenderWindow(renWin);
  // actor将添加到渲染器中。将创建初始摄影机视图。Dolly方法将摄影机移向FocalPoint，从而放大图像。
  aRenderer->AddActor(lens);
  aRenderer->AddActor(skin);
  aRenderer->SetActiveCamera(aCamera);
  aRenderer->ResetCamera();
  aCamera->Dolly(1.5);
//设置背景
  aRenderer->SetBackground(colors->GetColor3d("BkgColor").GetData());
  renWin->SetSize(640, 480);
  renWin->SetWindowName("TissueLens");

  aRenderer->ResetCameraClippingRange();

  renWin->Render();
  iren->Initialize();
  iren->Start();

  return EXIT_SUCCESS;
}