如何告诉 VTK 管道使用通过 TimerEvent 更新的新 vtkPolyData？

Question

意向

我编写了一个 VTK 应用程序，它使用 vtkPoints > vtkPolyLine > vtkPolyData > vtkPolyDataMapper 生成螺旋并显示它。如果在程序初始化时静态完成，这很好用。现在，我想动态添加新的数据点。目的是实时可视化测量结果，因此将在特定时间间隔添加新数据。

问题

目前，我刚刚实现了一个 TimerEvent 来更新 vtkPoints 和 vtkPolyLine。但是，该程序仅显示在启动 vtkRenderWindowInteractor 之前生成的静态数据。我还尝试对几乎所有对象使用“Modified()”和“Update()”调用，尝试删除、重新生成并向渲染器添加新角色——但没有成功！我在下面添加了我的 C++ 代码...

问题

如何告诉 VTK vtkPolyData 对象已经改变？
我应该仔细看看 VTK 用户指南中的哪一个？

详情/源代码

我正在使用 Visual Studio Community 2017 和 VTK 8.0.0，它们都编译为 Win32 目标。

#include <vtkAutoInit.h>
VTK_MODULE_INIT(vtkRenderingOpenGL2);
VTK_MODULE_INIT(vtkRenderingContextOpenGL2);
VTK_MODULE_INIT(vtkRenderingVolumeOpenGL2);
VTK_MODULE_INIT(vtkInteractionStyle);
VTK_MODULE_INIT(vtkRenderingFreeType);

#include <vtkSmartPointer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkConeSource.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkProperty.h>

#include <vtkPoints.h>
#include <vtkPolyLine.h>


vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();
vtkSmartPointer<vtkPolyLine> polyLine = vtkSmartPointer<vtkPolyLine>::New();

int numOfPoints = 0;
double t = 0;

void NextPoint() {
    double x = t * cos(t);
    double y = t * sin(t);
    points->InsertNextPoint(x, y, t);
    polyLine->GetPointIds()->InsertNextId(numOfPoints);

    numOfPoints++;
    t += 0.1;
}

vtkSmartPointer<vtkPolyData> generateEllipse() {
    // Add some points so we actually see something at all...
    for (int i = 0; i < 100; ++i) {
        NextPoint();
    }

    vtkSmartPointer<vtkCellArray> cells = vtkSmartPointer<vtkCellArray>::New();
    cells->InsertNextCell(polyLine);

    vtkSmartPointer<vtkPolyData> polyData = vtkSmartPointer<vtkPolyData>::New();
    polyData->SetPoints(points);
    polyData->SetLines(cells);
    
    return polyData;
}


class vtkTimerCallback : public vtkCommand
{
public:
    static vtkTimerCallback *New()
    {
        vtkTimerCallback *cb = new vtkTimerCallback;
        cb->TimerCount = 0;
        return cb;
    }

    virtual void Execute(vtkObject *vtkNotUsed(caller), unsigned long eventId,
        void *vtkNotUsed(callData))
    {
        if (vtkCommand::TimerEvent == eventId)
        {
            NextPoint(); // Add another point to polyData

            ++this->TimerCount;
            cout << this->TimerCount << endl;
        }
        
    }

private:
    int TimerCount;

};



int main(int argc, char** argv) {
    vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();

    vtkSmartPointer<vtkRenderWindowInteractor> rwi = vtkSmartPointer<vtkRenderWindowInteractor>::New();
    rwi->SetRenderWindow(renderWindow);

    vtkSmartPointer<vtkPolyData> data = generateEllipse();

    vtkSmartPointer<vtkPolyDataMapper> mapper = vtkSmartPointer<vtkPolyDataMapper>::New();
    mapper->SetInputData(data);

    vtkSmartPointer<vtkActor> actor = vtkSmartPointer<vtkActor>::New();
    actor->SetMapper(mapper);
    actor->GetProperty()->SetDiffuseColor(255, 255, 0);

    vtkSmartPointer<vtkRenderer> renderer = vtkSmartPointer<vtkRenderer>::New();
    renderWindow->AddRenderer(renderer);
    renderer->AddActor(actor);
    renderer->ResetCamera();

    renderWindow->Render();
    
    // Add Timer Event...
    rwi->Initialize();
    vtkSmartPointer<vtkTimerCallback> cb = vtkSmartPointer<vtkTimerCallback>::New();
    rwi->AddObserver(vtkCommand::TimerEvent, cb);
    int timerId = rwi->CreateRepeatingTimer(100); // every 100ms
    std::cout << "timerId: " << timerId << std::endl;

    // Start Displaying...
    rwi->Start();

    return 0;
}

Answer 1

问题是单元格不是通过指针存储的 - 当您调用 cells->InsertNextCell(polyLine); 时，数据被复制，而不是指向，以便在数组中创建单元格的有效存储（整个实现实际上在 vtkCellArray 的 header 中，因此您可以查看它）。所以当你更新 polyLine 时，它对 polydata 没有影响，因为 polydata 有自己的副本，你没有更新。以下代码对我有用（你必须公开 polydata 和 cellArray）：

virtual void Execute(vtkObject *vtkNotUsed(caller), unsigned long eventId,
    void *vtkNotUsed(callData))
{
    if (vtkCommand::TimerEvent == eventId)
    {
        NextPoint(); // Add another point to polyData

        cells->Initialize(); // reset the cells to remove the old spiral
        cells->InsertNextCell(polyLine); // re-insert the updated spiral
        cells->Modified(); // required to update
        data->Modified(); // required to update
        ++this->TimerCount;
        cout << polyLine->GetNumberOfPoints() << endl;
        renderWindow->Render(); // refresh the render window after each update
    }
}

Answer 2

昨天我制定了一个替代解决方案，使用 vtkProgrammableDataObjectSource 作为数据源。 Tomj 的解决方案是更直接和简单的解决方案...但是，vtk.org 中没有 C++ 示例代码解释如何使用 vtkProgrammableDataObjectSource，我不得不通过反复试验来解决它。所以我将 post 放在这里，因为它可能对其他人有帮助：

#include <vtkAutoInit.h>
VTK_MODULE_INIT(vtkRenderingOpenGL2);
VTK_MODULE_INIT(vtkRenderingContextOpenGL2);
VTK_MODULE_INIT(vtkRenderingVolumeOpenGL2);
VTK_MODULE_INIT(vtkInteractionStyle);
VTK_MODULE_INIT(vtkRenderingFreeType);

#include <vtkSmartPointer.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkConeSource.h>
#include <vtkPolyDataMapper.h>
#include <vtkActor.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkProperty.h>
#include <vtkPoints.h>
#include <vtkPolyLine.h>
#include <vtkProgrammableFilter.h>
#include <vtkCallbackCommand.h>
#include <vtkPolyDataStreamer.h>

#include <vtkProgrammableDataObjectSource.h>


vtkSmartPointer<vtkProgrammableDataObjectSource> pDOS = vtkSmartPointer<vtkProgrammableDataObjectSource>::New();
vtkSmartPointer<vtkRenderer> renderer = vtkSmartPointer<vtkRenderer>::New();

vtkSmartPointer<vtkPoints> points = vtkSmartPointer<vtkPoints>::New();
vtkSmartPointer<vtkPolyLine> polyLine = vtkSmartPointer<vtkPolyLine>::New();

int numOfPoints = 0;
double t = 0;

void NextPoint() {
    double x = t * cos(t);
    double y = t * sin(t);
    points->InsertNextPoint(x, y, t);
    polyLine->GetPointIds()->InsertNextId(numOfPoints);

    numOfPoints++;
    t += 0.1;
}

void generateEllipse(void *caller) {
    vtkProgrammableDataObjectSource *pDOS = vtkProgrammableDataObjectSource::SafeDownCast((vtkObjectBase*)caller);

    vtkSmartPointer<vtkCellArray> cells = vtkSmartPointer<vtkCellArray>::New();
    cells->InsertNextCell(polyLine);

    vtkSmartPointer<vtkPolyData> polyData = vtkSmartPointer<vtkPolyData>::New();
    polyData->SetPoints(points);
    polyData->SetLines(cells);

    pDOS->SetOutput(polyData);
}


int counter2 = 0;
void TimerCallbackFunction(vtkObject* caller, long unsigned int vtkNotUsed(eventId), void* clientData, void* vtkNotUsed(callData)) {
    cout << "timer callback: " << counter2 << endl;

// To avoid globals we can implement this later... 
//  vtkSmartPointer<vtkProgrammableDataObjectSource> pDOS =
//      static_cast<vtkProgrammableDataObjectSource*>(clientData);

    vtkRenderWindowInteractor *rwi =
        static_cast<vtkRenderWindowInteractor*>(caller);

    NextPoint();

    pDOS->Modified();
    rwi->Render();
    renderer->ResetCamera(); // Optional: Reposition Camera, so it displays the whole object

    counter2++;
}



int main(int argc, char** argv) {
    vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();

    vtkSmartPointer<vtkRenderWindowInteractor> rwi = vtkSmartPointer<vtkRenderWindowInteractor>::New();
    rwi->SetRenderWindow(renderWindow);


    pDOS->SetExecuteMethod(&generateEllipse, pDOS);

    vtkSmartPointer<vtkPolyDataMapper> mapper = vtkSmartPointer<vtkPolyDataMapper>::New();
    mapper->SetInputConnection(pDOS->GetOutputPort());

    vtkSmartPointer<vtkActor> actor = vtkSmartPointer<vtkActor>::New();
    actor->SetMapper(mapper);
    actor->GetProperty()->SetDiffuseColor(255, 255, 0);

    renderWindow->AddRenderer(renderer);
    renderer->AddActor(actor);
    renderer->ResetCamera();

    renderWindow->Render();

    // Add Timer Event...
    vtkSmartPointer<vtkCallbackCommand> timerCallback = vtkSmartPointer<vtkCallbackCommand>::New();
    timerCallback->SetCallback(TimerCallbackFunction);

    rwi->Initialize();
    rwi->CreateRepeatingTimer(100);
    rwi->AddObserver(vtkCommand::TimerEvent, timerCallback);


    // Start Displaying...
    rwi->Start();

    return 0;
}

如何告诉 VTK 管道使用通过 TimerEvent 更新的新 vtkPolyData？

How to tell VTK pipeline to use new vtkPolyData updated via TimerEvent?

c++

vtk

意向

问题

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详情/源代码