VTK_Learning_体绘制裁剪_Cripping技术

我会带着你远行 2023-07-12 09:20 1阅读 0赞

# 1.基于Clipping的体绘制裁剪技术 #

Clipping技术支持VTKImageData和VTKUntructuredGrid数据类型。该功能由vtkAbstractMapper3D类提供，对于那些使用基于OpenGL的硬件裁剪技术的Mapper类，如vtkPolyDataMapper、vtkVolumeTextureMapper2D、VTKProjectedTetrahedraMapper等，当设置的裁剪面个数超过OpenGL支持的个数（一般为6）时，VTK会反馈一个错误；而对于基于软件的裁剪技术的Mapper类，如vtkVolumeRayCastMapper则没有这些限制，可以支持任意多个裁剪面。使用Clipping技术，可以沿着任意方向将图像切开，便于观察体数据内部细节。  
下面是例程中的一个实验：

#include <vtkAutoInit.h>
    VTK_MODULE_INIT(vtkRenderingOpenGL);
    VTK_MODULE_INIT(vtkRenderingVolumeOpenGL);
    VTK_MODULE_INIT(vtkRenderingFreeType);
    VTK_MODULE_INIT(vtkInteractionStyle);
     
    #include <vtkSmartPointer.h>
    #include <vtkPlane.h>
    #include <vtkStructuredPoints.h>
    #include <vtkStructuredPointsReader.h>
    #include <vtkGPUVolumeRayCastMapper.h>
    #include <vtkVolumeProperty.h>
    #include <vtkPiecewiseFunction.h>
    #include <vtkColorTransferFunction.h>
    #include <vtkVolume.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkCamera.h>
     
    int main()
    {
    	vtkSmartPointer<vtkStructuredPointsReader> reader =
    		vtkSmartPointer<vtkStructuredPointsReader>::New();
    	reader->SetFileName("mummy.128.vtk");
    	reader->Update();
     
    	vtkSmartPointer<vtkGPUVolumeRayCastMapper> origMapper =
    		vtkSmartPointer<vtkGPUVolumeRayCastMapper>::New();
    	origMapper->SetInputData(reader->GetOutput());
     
    	vtkSmartPointer<vtkGPUVolumeRayCastMapper> volumeMapper =
    		vtkSmartPointer<vtkGPUVolumeRayCastMapper>::New();
    	volumeMapper->SetInputData(reader->GetOutput());
     
    	vtkSmartPointer<vtkPlane> plane =
    		vtkSmartPointer<vtkPlane>::New();
    	plane->SetOrigin(120, 120, 0);
    	plane->SetNormal(1, 1, 0);
    	volumeMapper->AddClippingPlane(plane);
     
    	/*****************************************************************/
    	//设置体绘制相关属性
    	vtkSmartPointer<vtkVolumeProperty> volumeProperty =
    		vtkSmartPointer<vtkVolumeProperty>::New();
    	volumeProperty->SetInterpolationTypeToLinear(); //设置线性插值方式
    	volumeProperty->ShadeOn();//开启阴影属性
    	volumeProperty->SetAmbient(0.4);//设置环境温度
    	volumeProperty->SetDiffuse(0.6);//设置漫反射系数
    	volumeProperty->SetSpecular(0.2);//设置镜面反射系数
    	//添加灰度不透明度属性
    	vtkSmartPointer<vtkPiecewiseFunction> compositeOpacity =
    		vtkSmartPointer<vtkPiecewiseFunction>::New();
    	compositeOpacity->AddPoint(70, 0.0);
    	compositeOpacity->AddPoint(90, 0.4);
    	compositeOpacity->AddPoint(180, 0.6);
    	volumeProperty->SetScalarOpacity(compositeOpacity);
    	//添加梯度不同明度属性
    	vtkSmartPointer<vtkPiecewiseFunction> gradientOpacity =
    		vtkSmartPointer<vtkPiecewiseFunction>::New();
    	gradientOpacity->AddPoint(10, 0.0);
    	gradientOpacity->AddPoint(90, 0.5);
    	gradientOpacity->AddPoint(100, 1.0);
    	volumeProperty->SetGradientOpacity(gradientOpacity);
    	//添加颜色传输
    	vtkSmartPointer<vtkColorTransferFunction> color =
    		vtkSmartPointer<vtkColorTransferFunction>::New();
    	color->AddRGBPoint(0, 0, 0, 0);
    	color->AddRGBPoint(64, 1.0, 0.52, 0.3);
    	color->AddRGBPoint(190.0, 1.00, 1.00, 1.00);
    	color->AddRGBPoint(220.0, 0.20, 0.20, 0.20);
    	volumeProperty->SetColor(color);
    	/***********************************************************/
    	//渲染管道
    	vtkSmartPointer<vtkVolume> origVolume =
    		vtkSmartPointer<vtkVolume>::New();
    	origVolume->SetMapper(origMapper);
    	origVolume->SetProperty(volumeProperty);
     
    	vtkSmartPointer<vtkVolume> clippingVolume =
    		vtkSmartPointer<vtkVolume>::New();
    	clippingVolume->SetMapper(volumeMapper);
    	clippingVolume->SetProperty(volumeProperty);
     
    	/
    	double origView[4] = { 0, 0, 0.5, 1 };
    	double croppingView[4] = { 0.5, 0, 1, 1 };
    	vtkSmartPointer<vtkRenderer> origRender =
    		vtkSmartPointer<vtkRenderer>::New();
    	origRender->AddVolume(origVolume);
    	origRender->SetBackground(1, 1, 0);
    	origRender->SetViewport(origView);
     
    	vtkSmartPointer<vtkRenderer> clippingRender =
    		vtkSmartPointer<vtkRenderer>::New();
    	clippingRender->AddVolume(clippingVolume);
    	clippingRender->SetBackground(0, 1, 0);
    	clippingRender->SetViewport(croppingView);
    	///
    	vtkSmartPointer<vtkRenderWindow> rw =
    		vtkSmartPointer<vtkRenderWindow>::New();
    	rw->AddRenderer(origRender);
    	rw->AddRenderer(clippingRender);
    	rw->SetWindowName("Cropping Volume");
    	rw->SetSize(640, 320);
     
    	vtkSmartPointer<vtkRenderWindowInteractor> rwi =
    		vtkSmartPointer<vtkRenderWindowInteractor>::New();
    	rwi->SetRenderWindow(rw);
     
    	origRender->GetActiveCamera()->SetPosition(0, -1, 0);
    	origRender->GetActiveCamera()->SetFocalPoint(0, 0, 0);
    	origRender->GetActiveCamera()->SetViewUp(0, 0, 1);
    	origRender->GetActiveCamera()->Azimuth(30);
    	origRender->GetActiveCamera()->Elevation(30);
    	origRender->ResetCamera();
    	clippingRender->SetActiveCamera(origRender->GetActiveCamera());
     
    	rw->Render();
    	rwi->Start();
    	return 0;
    }

从上面代码中可以看出，只需定义一个VTKPlane类型的裁剪平面对象，然后通过vtkAbstractMapper3D::AddClippingplane()函数将该平面添加到Mapper对象中即可。

输出结果为：

![20170207141938074][]

转换一个角度观察：

![20170207142005469][]

[20170207141938074]: https://img-blog.csdn.net/20170207141938074
[20170207142005469]: https://img-blog.csdn.net/20170207142005469