之前学习VTK多边形vtkPolyData类时，vtkPolyData内部是由几何结构和拓扑结构组成。
几何结构是离散点坐标组成，是点的集合；
拓扑结构是描述离散点之间的相互关系的信息，拓扑结构的最小组成单位是单元，每个单元是由几个点的vtkIdType描述的；不同个数的点ID可以描述三角、四边、多边、立体图形等各种图元信息；
定义单元需要指定单元的类型以及一些有序的点ID（vtkIdType）；
使用vtkPolyData创建多边形，需要输入点集合、单元集合、标量集合；
立方体有八个顶点、六个面以及十二条边组成；在可视化中，使用六个面就能组成立方体；那么在立方体的vtkPolyData中几何结构就是八个顶点，拓扑结构就是八个顶点分别组合的六个面；
步骤：
1.设定立方体的边长为1，起点从(0,0,0)开始；将八个顶点放入vtkPoints points中；
2.根据八个顶点的ID，组成vtkIdType pts[6][4]，pts中每行表示一个单元信息，是由4个点id组成的四边形；注意：这些id必须按照顺时针或逆时针方向排列。
3.将每个点对应的标量属性数据放入vtkFloatArray，标量数据个数必须与点的个数相同；
#include "vtkCellArray.h"
#include "vtkFloatArray.h"
#include "vtkPointData.h"
#include "vtkPoints.h"
#include "vtkPolyData.h"
#include "vtkPolyDataMapper.h"
#include "vtkCamera.h"
#include "vtkActor.h"
#include "vtkRenderer.h"
#include "vtkRenderWindow.h"
#include "vtkRenderWindowInteractor.h"
#include "vtkInteractorStyleImage.h"
#include "vtkAutoInit.h"
VTK_MODULE_INIT(vtkRenderingOpenGL2);
VTK_MODULE_INIT(vtkInteractionStyle);
int main() {
int i;
static float x[8][3] = {
{0,0,0},{1,0,0},{1,1,0},{0,1,0},
{0,0,1},{1,0,1},{1,1,1},{0,1,1}
};
static vtkIdType pts[6][4] = {
{0,1,2,3},{4,5,6,7},{0,1,5,4},
{1,2,6,5},{2,3,7,6},{3,0,4,7}
};
vtkNew cube;
vtkNew points;
vtkNew polys;
vtkNew scalars;
for (int i = 0; i < 8; i++) points->InsertPoint(i, x[i]);
for (int i = 0; i < 6; i++) polys->InsertNextCell(4, pts[i]);
for (int i = 0; i < 8; i++) scalars->InsertTuple1(i, i);
cube->SetPoints(points);
cube->SetPolys(polys);
cube->GetPointData()->SetScalars(scalars);
vtkNew cubeMapper;
cubeMapper->SetInputData(cube);
cubeMapper->SetScalarRange(0, 7);
vtkNew cubeActor;
cubeActor->SetMapper(cubeMapper);
vtkNew camera;
camera->SetPosition(1, 1, 1);
camera->SetFocalPoint(0, 0, 0);
vtkNew renderer;
vtkNew renWin;
renWin->AddRenderer(renderer);
vtkNew iren;
iren->SetRenderWindow(renWin);
renderer->AddActor(cubeActor);
renderer->SetActiveCamera(camera);
renderer->ResetCamera();
renderer->SetBackground(1, 1, 1);
renWin->SetSize(300, 300);
renWin->Render();
iren->Initialize();
iren->Start();
return 0;
}
使用SetLines，显示多边形的边框线；
vtkNew四面体cube; vtkNew points; vtkNew lines; for (int i = 0; i < 8; i++) points->InsertPoint(i, x[i]); lines->InsertNextCell(5); for (unsigned long i = 0; i < 4; ++i) { lines->InsertCellPoint(i); } lines->InsertCellPoint(0); lines->InsertNextCell(5); for (unsigned long i = 0; i < 4; ++i) { lines->InsertCellPoint(i + 4); } lines->InsertCellPoint(4); for (int i = 0; i < 4; i++) { lines->InsertNextCell(2); lines->InsertCellPoint(i); lines->InsertCellPoint(i + 4); } cube->SetPoints(points); cube->SetLines(lines);
四面体是由四个三角面和四个顶点组成；
参照立方体的做法，polys是由四个三角形组成；
const int num_points = 4;
static float x[num_points][3] = {
{0,0,0},{1,0,0},{0.5,1,0},{0.5,0.5,1}
};
static vtkIdType pts[4][3] = {
{0,1,2},{0,1,3},{1,2,3},{0,2,3}
};
vtkNew cube;
vtkNew points;
vtkNew polys;
vtkNew scalars;
for (int i = 0; i < num_points; i++) points->InsertPoint(i, x[i]);
for (int i = 0; i < 4; i++) polys->InsertNextCell(3, pts[i]);
for (int i = 0; i < num_points; i++) scalars->InsertTuple1(i, i);
cube->SetPoints(points);
cube->SetPolys(polys);
cube->GetPointData()->SetScalars(scalars);
vtkNew金字塔cube; vtkNew points; vtkNew lines; for (int i = 0; i < num_points; i++) points->InsertPoint(i, x[i]); for (int i = 0; i < num_points - 1; i++) { lines->InsertNextCell(2); lines->InsertCellPoint(i); lines->InsertCellPoint(num_points - 1); lines->InsertNextCell(2); lines->InsertCellPoint(i); lines->InsertCellPoint((i + 1) % (num_points - 1)); } cube->SetPoints(points); cube->SetLines(lines);
金字塔形状，由五个顶点和五个面，四个三角平面加上一个四边形平面；
参照立方体的做法，polys有两部分组成，一部分是形状相同的三角形，一部分是四边形；
#include "pch.h"
#include "vtkCellArray.h"
#include "vtkFloatArray.h"
#include "vtkPointData.h"
#include "vtkPoints.h"
#include "vtkPolyData.h"
#include "vtkPolyDataMapper.h"
#include "vtkCamera.h"
#include "vtkActor.h"
#include "vtkRenderer.h"
#include "vtkRenderWindow.h"
#include "vtkRenderWindowInteractor.h"
#include "vtkInteractorStyleImage.h"
#include "vtkAutoInit.h"
VTK_MODULE_INIT(vtkRenderingOpenGL2);
VTK_MODULE_INIT(vtkInteractionStyle);
int main() {
const int num_points = 5;
static float x[num_points][3] = {
{0,0,0},{1,0,0},{1,1,0},{0,1,0},{0.5,0.5,1}
};
static vtkIdType pts[4][3] = {
{0,1,4},{1,2,4},{2,3,4},{3,0,4}
};
vtkNew cube;
vtkNew points;
vtkNew polys;
vtkNew scalars;
for (int i = 0; i < num_points; i++) points->InsertPoint(i, x[i]);
for (int i = 0; i < 4; i++) polys->InsertNextCell(3, pts[i]);
polys->InsertNextCell(4);
for (int i = 0; i < 4; i++) {
polys->InsertCellPoint(i);
}
for (int i = 0; i < num_points; i++) scalars->InsertTuple1(i, i);
cube->SetPoints(points);
cube->SetPolys(polys);
cube->GetPointData()->SetScalars(scalars);
vtkNew cubeMapper;
cubeMapper->SetInputData(cube);
cubeMapper->SetScalarRange(0, 7);
vtkNew cubeActor;
cubeActor->SetMapper(cubeMapper);
vtkNew camera;
camera->SetPosition(1, 1, 1);
camera->SetFocalPoint(0, 0, 0);
vtkNew renderer;
vtkNew renWin;
renWin->AddRenderer(renderer);
vtkNew iren;
iren->SetRenderWindow(renWin);
renderer->AddActor(cubeActor);
renderer->SetActiveCamera(camera);
renderer->ResetCamera();
renderer->SetBackground(1, 1, 1);
renWin->SetSize(300, 300);
renWin->Render();
iren->Initialize();
iren->Start();
return 0;
}
使用四面体的边框绘制代码，绘制金字塔的边框线；
