VTK体绘制可视化问题

Question

我正在使用C++的vtk库来生成和可视化一些具有给定颜色和透明度映射的合成体素数据。下面展示了一个例子： 如图所示，数据通常是3D的，它工作得非常好。但是，在特定情况下，当数据变成2D时，可视化窗口将什么也没有显示。

我在此发布我的一些代码行，这可能会有所帮助。

imageData = vtkSmartPointer<vtkImageData>::New();
imageData->SetDimensions(X1, X2, X3); //For 2D, one of X1,X2 & X3=1
imageData->AllocateScalars(VTK_INT, 1);
int* I = new int[X1X2X3](); //int X1X2X3 = X1*X2*X3
I = static_cast<int*>(imageData->GetScalarPointer());

请注意，对于2D情况，X1=1或者X2=1或者X3=1。 有什么建议吗？

编辑： 我添加了一个等价的代码，它将展示我面临的确切问题：

main.cpp

//#include <vtkAutoInit.h> // if not using CMake to compile, necessary to use this macro
//#define vtkRenderingCore_AUTOINIT 3(vtkInteractionStyle, vtkRenderingFreeType, vtkRenderingOpenGL2)
//#define vtkRenderingVolume_AUTOINIT 1(vtkRenderingVolumeOpenGL2)
//#define vtkRenderingContext2D_AUTOINIT 1(vtkRenderingContextOpenGL2)
#include <vtkSmartPointer.h>
#include <vtkActor.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkSmartVolumeMapper.h>
#include <vtkColorTransferFunction.h>
#include <vtkVolumeProperty.h>
#include <vtkSampleFunction.h>
#include <vtkPiecewiseFunction.h>
#include <vtkImageData.h>
#include <stdlib.h>
using namespace std;

int main()
{
    //Declaring Variables
    vtkSmartPointer<vtkImageData> imageData;
    vtkSmartPointer<vtkVolumeProperty> volumeProperty;
    vtkSmartPointer<vtkPiecewiseFunction> compositeOpacity;
    vtkSmartPointer<vtkColorTransferFunction> color;
    vtkSmartPointer<vtkVolume> volume;
    vtkSmartPointer<vtkSmartVolumeMapper> mapper;
    vtkSmartPointer<vtkActor> actor;
    vtkSmartPointer<vtkRenderer> renderer;
    vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor;
    vtkSmartPointer<vtkRenderWindow> renderWindow;
    int* I;
    int X1, X2, X3, X1X2X3;

    //Assigning Values , Allocating Memory
    X1 = 10;
    X2 = 10;
    X3 = 10;
    X1X2X3 = X1*X2*X3;
    I = new int[X1X2X3]();
    imageData = vtkSmartPointer<vtkImageData>::New();
    volumeProperty = vtkSmartPointer<vtkVolumeProperty>::New();
    compositeOpacity = vtkSmartPointer<vtkPiecewiseFunction>::New();
    color = vtkSmartPointer<vtkColorTransferFunction>::New();
    volume = vtkSmartPointer<vtkVolume>::New();
    mapper = vtkSmartPointer<vtkSmartVolumeMapper>::New();
    actor = vtkSmartPointer<vtkActor>::New();
    renderer = vtkSmartPointer<vtkRenderer>::New();
    renderWindowInteractor = vtkSmartPointer<vtkRenderWindowInteractor>::New();
    renderWindow = vtkSmartPointer<vtkRenderWindow>::New(); 
    volumeProperty->ShadeOff();
    volumeProperty->SetInterpolationType(0);
    volumeProperty->SetColor(color);
    volumeProperty->SetScalarOpacity(compositeOpacity);
    imageData->SetDimensions(X1, X2, X3);
    imageData->AllocateScalars(VTK_INT, 1);
    I = static_cast<int*>(imageData->GetScalarPointer());
    renderWindow->AddRenderer(renderer);
    renderWindowInteractor->SetRenderWindow(renderWindow);
    renderer->SetBackground(0.5, 0.5, 0.5);
    renderWindow->SetSize(800, 800);    
    mapper->SetBlendModeToComposite();
    imageData->UpdateCellGhostArrayCache();
    mapper->SetRequestedRenderModeToRayCast();
    mapper->SetInputData(imageData);
    volume->SetMapper(mapper);
    volume->SetProperty(volumeProperty);
    renderer->AddViewProp(volume);
    volumeProperty->ShadeOff();

    //Setting Voxel Data and Its Properties
    for (int i = 0; i < X1X2X3; i++)
    {
        I[i] = i;
        compositeOpacity->AddPoint(i, 1);
        color->AddRGBPoint(i, double( rand()) / RAND_MAX, double(rand()) / RAND_MAX, double(rand()) / RAND_MAX);
    }

    renderer->ResetCamera();
    renderWindow->Render();
    renderWindowInteractor->Start();
    getchar();
    return 0;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.0)
project(EvoSim)
set(CMAKE_CXX_STANDARD 14)
set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS ON)
set(CMAKE_USE_RELATIVE_PATHS ON)
#GRABBING VTK
find_package(VTK REQUIRED)
include(${VTK_USE_FILE})

add_executable(MAIN main.cpp)
target_link_libraries(MAIN ${VTK_LIBRARIES})

这将导致以下输出（对于X1=X2=X3=10） 但是，如果我将X1设为1，则输出窗口为空。

编辑：

我刚刚观察到，在屏幕上显示的沿某个维度的体素数量总是比该维度中最大的体素数量少一个。例如，如果X1=X2=X3=10，则在vtkwindow中显示的每个维度的体素数为9。这不是我的期望结果。我认为这是X1=1的问题，导致0个体素被显示。有什么建议吗？

- Harsh Kumar Narula

---

你的数据不是真正意义上的二维，而只是一个体素单层吗？你是否检查过单层图像数据中的细胞数量是否符合你的预期？也许存在某种编号问题，但没有看到更多你的代码很难说清楚。 - mululu

是的，它只是一个体素的单层。我已经检查了单层图像数据中的单元格数量，与预期相符。我很快会发布最简等效代码。 - Harsh Kumar Narula

Answer 1

这个问题长期未得到解答，所以我添加了我的解决方案/解决方法。我不得不在imagedata的每个维度中添加一个额外的虚拟层。[在代码的imageData->SetDimensions(X1 +1 , X2 + 1, X3 + 1);这一行中可以看到]。其余部分都很容易理解。

#pragma once
//#include <vtkAutoInit.h> // if not using CMake to compile, necessary to use this macro
//#define vtkRenderingCore_AUTOINIT 3(vtkInteractionStyle, vtkRenderingFreeType, vtkRenderingOpenGL2)
//#define vtkRenderingVolume_AUTOINIT 1(vtkRenderingVolumeOpenGL2)
//#define vtkRenderingContext2D_AUTOINIT 1(vtkRenderingContextOpenGL2)
#include <vtkSmartPointer.h>
#include <vtkActor.h>
#include <vtkRenderWindow.h>
#include <vtkRenderer.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkSmartVolumeMapper.h>
#include <vtkColorTransferFunction.h>
#include <vtkVolumeProperty.h>
#include <vtkSampleFunction.h>
#include <vtkPiecewiseFunction.h>
#include <vtkImageData.h>
#include <stdlib.h>
#include <numeric>      // std::iota
using namespace std;

int main()
{
    //Declaring Variables
    vtkSmartPointer<vtkImageData> imageData;
    vtkSmartPointer<vtkVolumeProperty> volumeProperty;
    vtkSmartPointer<vtkPiecewiseFunction> compositeOpacity;
    vtkSmartPointer<vtkColorTransferFunction> color;
    vtkSmartPointer<vtkVolume> volume;
    vtkSmartPointer<vtkSmartVolumeMapper> mapper;
    vtkSmartPointer<vtkActor> actor;
    vtkSmartPointer<vtkRenderer> renderer;
    vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor;
    vtkSmartPointer<vtkRenderWindow> renderWindow;
    int X1, X2, X3, X1X2X3;
    //Assigning Values , Allocating Memory
    X1 = 10;
    X2 = 10;
    X3 = 10;
    X1X2X3 = X1*X2*X3;
    imageData = vtkSmartPointer<vtkImageData>::New();
    imageData->SetDimensions(X1 + 1, X2 + 1, X3 + 1);
    imageData->AllocateScalars(VTK_INT, 1);
    volumeProperty = vtkSmartPointer<vtkVolumeProperty>::New();
    compositeOpacity = vtkSmartPointer<vtkPiecewiseFunction>::New();
    color = vtkSmartPointer<vtkColorTransferFunction>::New();
    volume = vtkSmartPointer<vtkVolume>::New();
    mapper = vtkSmartPointer<vtkSmartVolumeMapper>::New();
    actor = vtkSmartPointer<vtkActor>::New();
    renderer = vtkSmartPointer<vtkRenderer>::New();
    renderWindowInteractor = vtkSmartPointer<vtkRenderWindowInteractor>::New();
    renderWindow = vtkSmartPointer<vtkRenderWindow>::New();
    volumeProperty->ShadeOff();
    volumeProperty->SetInterpolationType(0);
    volumeProperty->SetColor(color);
    volumeProperty->SetScalarOpacity(compositeOpacity);
    imageData->AllocateScalars(VTK_INT, 1);
    renderWindow->AddRenderer(renderer);
    renderWindowInteractor->SetRenderWindow(renderWindow);
    renderer->SetBackground(0.5, 0.5, 0.5);
    renderWindow->SetSize(800, 800);
    mapper->SetBlendModeToComposite();
    imageData->UpdateCellGhostArrayCache();
    mapper->SetRequestedRenderModeToRayCast();
    mapper->SetInputData(imageData);
    volume->SetMapper(mapper);
    volume->SetProperty(volumeProperty);
    renderer->AddViewProp(volume);
    volumeProperty->ShadeOff();

    //I is supposed to store the 3D data which has to be shown as volume visualization. This 3D data is stored 
    //as a 1D array in which the order of iteration over 3 dimensions is x->y->z, this leads to the following 
    //3D to 1D index conversion farmula index1D =  i + X1*j + X1*X2*k   
    vector<int> I(X1X2X3,0); // No need to use int* I = new int[X1X2X3] //Vectors are good
    std::iota(&I[0], &I[0] + X1X2X3, 1); //Creating dummy data as 1,2,3...X1X2X3

    //Setting Voxel Data and Its Properties
    for (int k = 0; k < X3 + 1 ; k++)   
    {
        for (int j = 0; j < X2 + 1 ; j++)
        {
            for (int i = 0; i < X1 + 1 ; i++)
            {
                int* voxel = static_cast<int*>(imageData->GetScalarPointer(i, j, k));

                if (i==X1 || j== X2 || k==X3)
                {
                    //Assigning zeros to dummy voxels, these will not be displayed anyways
                    voxel[0] = 0;
                }

                else
                {
                    //copying data from I to imagedata voxel
                    voxel[0] = I[i + X1*j + X1*X2*k];
                }               
            }
        }
    }

    //Setting Up Display Properties
    for (int i = 1; i < X1X2X3; i++)
    {
        compositeOpacity->AddPoint(i, 1);
        color->AddRGBPoint(i, double(rand()) / RAND_MAX, double(rand()) / RAND_MAX, double(rand()) / RAND_MAX);
    }

    renderer->ResetCamera();
    renderWindow->Render();
    renderWindowInteractor->Start();
    getchar();
    return 0;
}

现在，每个维度中预期的体素数量（如上面的代码所示为10）已正确显示。

- Harsh Kumar Narula