#ifndef INITIAL_OPENGL

#define INITIAL_OPENGL

#include <vtkAutoInit.h>

VTK_MODULE_INIT(vtkRenderingOpenGL)

VTK_MODULE_INIT(vtkInteractionStyle)

#endif

#include <iostream>

using namespace std;

#include <vtkVersion.h>

#include <vtkPolyData.h>

#include <vtkProperty.h>

#include <vtkMath.h>

#include <vtkSmartPointer.h>

#include <vtkPolyDataMapper.h>

#include <vtkActor.h>

#include <vtkRenderWindow.h>

#include <vtkRenderer.h>

#include <vtkRenderWindowInteractor.h>

#include <vtkImageData.h>

#include <vtkGreedyTerrainDecimation.h>

#include <vtkInteractorStyleTrackballCamera.h>

#include <vtkInteractionWidgetsModule.h>

void myShow(vtkGreedyTerrainDecimation* anInput)

{

    vtkSmartPointer<vtkPolyDataMapper> aMapper=vtkSmartPointer<vtkPolyDataMapper>::New();

    aMapper->SetInputConnection(anInput->GetOutputPort());

    aMapper->ScalarVisibilityOn();

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

    anActor->SetMapper(aMapper);

    anActor->GetProperty()->SetInterpolationToFlat();

    anActor->GetProperty()->EdgeVisibilityOn();

    anActor->GetProperty()->SetEdgeColor(1,0,0);

    vtkSmartPointer<vtkRenderer> ren1=vtkSmartPointer<vtkRenderer>::New();

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

    ren1->AddActor(anActor);

    ren1->ResetCamera();

    ren1->SetBackground(1,1,1);

    renWin->AddRenderer(ren1);

    renWin->SetSize(512,512);

    vtkSmartPointer<vtkRenderWindowInteractor> iren=vtkSmartPointer<vtkRenderWindowInteractor>::New();

    vtkSmartPointer<vtkInteractorStyleTrackballCamera> style=vtkSmartPointer<vtkInteractorStyleTrackballCamera>::New();

    iren->SetRenderWindow(renWin);

    iren->SetInteractorStyle(style);

    iren->Start();

}

int main()

{

    vtkSmartPointer<vtkImageData> image=vtkSmartPointer<vtkImageData>::New();

    image->SetDimensions(120,120,1);

    image->AllocateScalars(VTK_UNSIGNED_CHAR,1);

    int dims[3];

//    double max=sqrt(dims[0]*dims[0]+dims[1]*dims[1]);

    image->GetDimensions(dims);

    double R=100;//球面半径

    double r=0;//任意x、y坐标点，到（0，0）点的距离

    double r2=r*r;

    double rCrown=dims[0]/2;

    double rCrown2=rCrown*rCrown;//球冠半径的平方

    double hmax2=R*R-rCrown2;//最大弧矢高的平方

    double hmax=R-sqrt(hmax2);//最大弧矢高

    for(double i=0;i<dims[0];i++)

    {

        for(double j=0;j<dims[1];j++)

        {

            unsigned char* pixel=static_cast<unsigned char*>(image->GetScalarPointer(i,j,0));

            double x=(i-dims[0]/2),y=(j-dims[1]/2);

            r2=x*x+y*y;

            r=sqrt(r2);

            if(r<rCrown)

                //不知道为什么，要在后面多加一个最大弧矢高hmax，才能得到正确的球冠,大概是坐标方向问题吧

                pixel[0]=sqrt(R*R-r2)-(R-hmax)+hmax;

            else

                pixel[0]=hmax;

        }

    }

    vtkSmartPointer<vtkGreedyTerrainDecimation>decimation=vtkSmartPointer<vtkGreedyTerrainDecimation>::New();

    decimation->SetInputData(image);

    decimation->Update();

    //可视化

    myShow(decimation);

    return 0;

}

VTK初学一，a Mesh from vtkImageData—球冠