12. VTK上选取点（VTK7版本+VTK9版本）
这个专栏是用于记录我在学习VTK过程中的一些心得体会。参考的资料主要有以下三个：
1. 张晓东 罗火灵《VTK图形图像开发进阶》
2. https://examples.vtk.org/site/
3. 沈子恒 《VTK 三维数据渲染进阶》
遇到的一个大问题就是由于版本更新，这些资料中很多代码无法正常运行，需要进行一定的修改，所以这个专栏会记录下来我修改后的程序代码，以便于我之后温习。也希望能给和我有同样困扰的小伙伴们一些帮助。
我使用的版本：VTK9 + VS2022
VTK上选取点这个例子我主要是参考了官网的程序代码examples.vtk.org/site/Cxx/Picking/CellPicking/ 。
这个在我正在做的医学图像项目VS2022联合Qt5开发学习8（QT5.12.3联合VTK7在VS2022上开发医学图像项目3——医学图像可视化）-CSDN博客的后续功能上有用到，所以在这里记录一下。
VTK9版本
#include "vtkAutoInit.h"
VTK_MODULE_INIT(vtkRenderingOpenGL2);
VTK_MODULE_INIT(vtkInteractionStyle);
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
namespace {
// Catch mouse events.
class MouseInteractorStyle : public vtkInteractorStyleTrackballCamera
{
public:
static MouseInteractorStyle* New();
MouseInteractorStyle()
{
selectedMapper = vtkSmartPointer::New();
selectedActor = vtkSmartPointer::New();
}
virtual void OnLeftButtonDown() override
{
vtkNew colors;
// Get the location of the click (in window coordinates).
int* pos = this->GetInteractor()->GetEventPosition();
vtkNew picker;
picker->SetTolerance(0.0005);
// Pick from this location.
picker->Pick(pos[0], pos[1], 0, this->GetDefaultRenderer());
double* worldPosition = picker->GetPickPosition();
std::cout << "Cell id is: " << picker->GetCellId() << std::endl;
if (picker->GetCellId() != -1)
{
std::cout << "Pick position is: (" << worldPosition[0] << ", "
<< worldPosition[1] << ", " << worldPosition[2] << ")" << endl;
vtkNew ids;
ids->SetNumberOfComponents(1);
ids->InsertNextValue(picker->GetCellId());
vtkNew selectionNode;
selectionNode->SetFieldType(vtkSelectionNode::CELL);
selectionNode->SetContentType(vtkSelectionNode::INDICES);
selectionNode->SetSelectionList(ids);
vtkNew selection;
selection->AddNode(selectionNode);
vtkNew extractSelection;
extractSelection->SetInputData(0, this->Data);
extractSelection->SetInputData(1, selection);
extractSelection->Update();
// In selection
vtkNew selected;
selected->ShallowCopy(extractSelection->GetOutput());
std::cout << "Number of points in the selection: "
<< selected->GetNumberOfPoints() << std::endl;
std::cout << "Number of cells in the selection : "
<< selected->GetNumberOfCells() << std::endl;
selectedMapper->SetInputData(selected);
selectedActor->SetMapper(selectedMapper);
selectedActor->GetProperty()->EdgeVisibilityOn();
selectedActor->GetProperty()->SetColor(
colors->GetColor3d("Tomato").GetData());
selectedActor->GetProperty()->SetLineWidth(3);
this->Interactor->GetRenderWindow()
->GetRenderers()
->GetFirstRenderer()
->AddActor(selectedActor);
}
// Forward events.
vtkInteractorStyleTrackballCamera::OnLeftButtonDown();
}
vtkSmartPointer Data;
vtkSmartPointer selectedMapper;
vtkSmartPointer selectedActor;
};
vtkStandardNewMacro(MouseInteractorStyle);
} // namespace
int main(int, char* [])
{
vtkNew colors;
vtkNew planeSource;
planeSource->Update();
vtkNew triangleFilter;
triangleFilter->SetInputConnection(planeSource->GetOutputPort());
triangleFilter->Update();
vtkNew mapper;
mapper->SetInputConnection(triangleFilter->GetOutputPort());
vtkNew actor;
actor->GetProperty()->SetColor(colors->GetColor3d("SeaGreen").GetData());
actor->SetMapper(mapper);
vtkNew renderer;
vtkNew renderWindow;
renderWindow->AddRenderer(renderer);
renderWindow->SetWindowName("CellPicking");
vtkNew renderWindowInteractor;
renderWindowInteractor->SetRenderWindow(renderWindow);
renderWindowInteractor->Initialize();
// Set the custom stype to use for interaction.
vtkNew style;
style->SetDefaultRenderer(renderer);
style->Data = triangleFilter->GetOutput();
renderWindowInteractor->SetInteractorStyle(style);
renderer->AddActor(actor);
renderer->ResetCamera();
renderer->SetBackground(colors->GetColor3d("PaleTurquoise").GetData());
renderWindow->Render();
renderWindowInteractor->Start();
return EXIT_SUCCESS;
}
官网的代码，直接就可以用了。
运行结果
VTK上选取点
VTK7版本
因为我的医学图像项目用的是VTK7，上面的代码如果直接放在VTK7上大概会报十个错，主要问题是不存在从 XXX到 XXX的适当转换函数。
所以我又修改了一下代码，让它能在VTK7下正常运行。修改方法主要是用 .GetPointer() 方法获取指向对象的指针，并将其传递给需要原始指针的函数或方法。
#include "vtkAutoInit.h"
VTK_MODULE_INIT(vtkRenderingOpenGL2);
VTK_MODULE_INIT(vtkInteractionStyle);
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
namespace {
// Catch mouse events.
class MouseInteractorStyle : public vtkInteractorStyleTrackballCamera
{
public:
static MouseInteractorStyle* New();
MouseInteractorStyle()
{
selectedMapper = vtkSmartPointer::New();
selectedActor = vtkSmartPointer::New();
}
virtual void OnLeftButtonDown() override
{
vtkNew colors;
// Get the location of the click (in window coordinates).
int* pos = this->GetInteractor()->GetEventPosition();
vtkNew picker;
picker->SetTolerance(0.0005);
// Pick from this location.
picker->Pick(pos[0], pos[1], 0, this->GetDefaultRenderer());
double* worldPosition = picker->GetPickPosition();
std::cout << "Cell id is: " << picker->GetCellId() << std::endl;
if (picker->GetCellId() != -1)
{
std::cout << "Pick position is: (" << worldPosition[0] << ", "
<< worldPosition[1] << ", " << worldPosition[2] << ")" << endl;
vtkNew ids;
ids->SetNumberOfComponents(1);
ids->InsertNextValue(picker->GetCellId());
vtkNew selectionNode;
selectionNode->SetFieldType(vtkSelectionNode::CELL);
selectionNode->SetContentType(vtkSelectionNode::INDICES);
selectionNode->SetSelectionList(ids.GetPointer()); // 使用 .GetPointer() 获取指针
vtkNew selection;
selection->AddNode(selectionNode.GetPointer());
vtkNew extractSelection;
extractSelection->SetInputData(0, this->Data.GetPointer());
extractSelection->SetInputData(1, selection.GetPointer());
extractSelection->Update();
// In selection
vtkNew selected;
selected->ShallowCopy(extractSelection->GetOutput());
std::cout << "Number of points in the selection: "
<< selected->GetNumberOfPoints() << std::endl;
std::cout << "Number of cells in the selection : "
<< selected->GetNumberOfCells() << std::endl;
selectedMapper->SetInputData(selected.GetPointer());
selectedActor->SetMapper(selectedMapper);
selectedActor->GetProperty()->EdgeVisibilityOn();
selectedActor->GetProperty()->SetColor(
colors->GetColor3d("Tomato").GetData());
selectedActor->GetProperty()->SetLineWidth(3);
this->Interactor->GetRenderWindow()
->GetRenderers()
->GetFirstRenderer()
->AddActor(selectedActor);
}
// Forward events.
vtkInteractorStyleTrackballCamera::OnLeftButtonDown();
}
vtkSmartPointer Data;
vtkSmartPointer selectedMapper;
vtkSmartPointer selectedActor;
};
vtkStandardNewMacro(MouseInteractorStyle);
} // namespace
int main(int, char* [])
{
vtkNew colors;
vtkNew planeSource;
planeSource->Update();
vtkNew triangleFilter;
triangleFilter->SetInputConnection(planeSource->GetOutputPort());
triangleFilter->Update();
vtkNew mapper;
mapper->SetInputConnection(triangleFilter->GetOutputPort());
vtkMapper* mapperRawPtr = mapper.GetPointer(); // 获取指针
vtkNew actor;
vtkProp* actorRawPtr = actor.GetPointer();
actor->GetProperty()->SetColor(colors->GetColor3d("SeaGreen").GetData());
actor->SetMapper(mapperRawPtr);
vtkNew renderer;
vtkRenderer* rendererRawPtr = renderer.GetPointer(); // 获取指针
vtkNew renderWindow;
renderWindow->AddRenderer(rendererRawPtr);
renderWindow->SetWindowName("CellPicking");
vtkNew renderWindowInteractor;
vtkRenderWindow* renderWindowRawPtr = renderWindow.GetPointer();
renderWindowInteractor->SetRenderWindow(renderWindowRawPtr);
renderWindowInteractor->Initialize();
// Set the custom stype to use for interaction.
vtkNew style;
vtkInteractorObserver* styleRawPtr = style.GetPointer();
style->SetDefaultRenderer(rendererRawPtr);
style->Data = triangleFilter->GetOutput();
renderWindowInteractor->SetInteractorStyle(styleRawPtr);
renderer->AddActor(actorRawPtr);
renderer->ResetCamera();
renderer->SetBackground(colors->GetColor3d("PaleTurquoise").GetData());
renderWindow->Render();
renderWindowInteractor->Start();
return EXIT_SUCCESS;
}
不过我这么修改之后还是有个问题，运行之后是这个样子。
VTK7上选取点
感觉vtkCellPicker用起来还是没什么问题的，vtkTriangleFilter那里有点问题，再就是颜色那里可能VTK7里没有一些VTK9里设置的特殊颜色。颜色这里可以这么修改：
vtkNew actor;
vtkProp* actorRawPtr = actor.GetPointer();
//actor->GetProperty()->SetColor(colors->GetColor3d("SeaGreen").GetData());
vtkColor3d myColor;
myColor.Set(0.5, 0.8, 0.2); // 设置 RGB 值，范围在 [0, 1]
actor->GetProperty()->SetColor(myColor.GetData()); 这里注释掉的是原代码，下面三行是我自己设的颜色，后面涉及到颜色的地方也可以按照这个修改。
还有一个问题是，不管是VTK9还是VTK7版本的代码，运行时取点都不是很灵便，原因可能是这里
vtkNew picker;
picker->SetTolerance(0.0005); vtkCellPicker 是 VTK 提供的一个类，用于执行这种拾取操作。SetTolerance 方法用于设置 vtkCellPicker 对象的拾取容差。拾取容差是一个浮点数，用于控制拾取操作的精度。SetTolerance 方法的参数是一个介于 0 和 1 之间的浮点数，表示拾取容差的大小。默认值是 0.025，这通常对于大多数应用来说已经足够了。在这个代码拾取容差设置为了 0.0005，拾取操作是非常精确了，但可能会更难拾取到对象。这个就看后期个人需求自己改值吧。
版本问题真的是很闹心哇。联想到最近一段时间都在头秃地改怎么在.stl图像上取点做切面然后实时更新，总是出问题，很难不怀疑是版本的锅。可是我现在一定得用VTK7，不然就得大改代码 ORZ。如果有朋友有比较好的用VTK7在qvtkWidget显示的.stl三维图像上取点做切面解决方案，欢迎在这个博客下留言（TAT帮帮我，琢磨了好几天了，头发要被我自己揪秃了）。