VTK开发笔记（三）：熟悉VTK开发流程，编写球体，多半透明球体Demo

前言

开始vtk实战，了解vtk的一些基本框架，通过代码是最好的方式。本篇实现一个vtk实现多球体半透明的Demo。

Demo

下面是osg存在的问题：

坐标系

计算机图形学里常用的坐标系统主要有4中，分别是model坐标系统、world坐标系统、view坐标系统和Display坐标系统。

Model坐标系统：定义模型时所采用的坐标系统，笛卡尔坐标系。
World坐标系统：actor（渲染模型）的三维控件坐标系，就是世界坐标系。每一个 actor可以通过缩放、旋转、平移等操作讲model坐标系放入world，就是三维相对坐标系变换。World坐标系也是相机和灯光所在的坐标系。
View坐标系统：相机能看见的坐标系统，XYZ轴取值都为[-1,1]，表示平面上的位置，Z值表示到相机的距离。
Display坐标系统 ：屏幕坐标系，坐标轴取值就是像素。

可视化管线渲染流程

数据源->多线段数据映射->【演员->渲染器->渲染窗口】。复杂一点的渲染管线：

Source：用于创建数据或者读取数据，跟字面意义一样是数据源。Source可作为Filter的输入，进行数据的过滤，生成新的数据。
Filter：特定规则进行处理过滤，比如轮廓线、比如剖面，更多的后续再讲究。
Mapper：映射器，更多的后续再讲究。

智能指针

智能指针会自动管理引用计数的增加或者减少，这个概念在编程语言中有，在ogs中也有，且使用方式基本一致。当指针{}作用域过了，其智能指针实际还存在，只有在其计数为0时，此时没有对象使用它了，则会销毁。

cpp 复制代码

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

智能指针类型可以作为函数返回值，正确的写法如下：

cpp 复制代码

vtkSmartPointer<vtkImageData> MyFunction()
{
    vtkSmartPointer<vtkImageData> myObject = vtkSmartPointer<vtkImageData>::New();
    return myObject;
}

函数MyFunction()的返回值是通过复制的方式，讲数据赋值给调用的变量，因此该数据的引用计数保持不变，而且函数MyFunction里的myObject也不会删除。反过来，要是函数里面定义是智能指针类型，返回类型是指针，其计数会减去1，示例如下：

cpp 复制代码

vtkImageData * MyFunction()
{
    vtkSmartPointer<vtkImageData> myObject = vtkSmartPointer<vtkImageData>::New();
return myObject;
}
vtkImageData *pImageData = MyFunction();

（注意：这里有点拗口难理解，为什么返回指针就-1，osg处理这块是无所谓的，混合了代码做过osg的测试，并不会崩溃，但是vtk说是会崩溃） Vtk的智能指针，还有一个注意点，就是一个智能指针的对象，在第一次赋值的时候，智能指针会分配对象相关的内存，初始化引用计数，后续不能再把这个指针更换对象，否则会引用计数出错，以上这几个点，都要注意，其在osg的智能指针中没这些讲究，比较完善，但是vtk如果使用智能指针，就要遵循这些，会轻微增加代码，主要是函数返回类型和赋值给的变量类型定义这两块为主。

绘制一个球体

步骤一：创建球体数据源

步骤二：创建多边形映射器

步骤三：创建演员类（类似osg模型结点）

步骤四：创建渲染器

步骤五：设置渲染器到渲染窗口

源码

VTKManager.cpp

cpp 复制代码

vtkSmartPointer<vtkSphereSource> VTKManager::createSphereSource(double x, double y, double z, double r, int vNum, int hNum)
{
    /*
     * 继承关系:
     * vktObject ---> vtkAlhorithm ---> vtkPolyDataAlgorithm ---> vtkSphereSource
     * 渲染关系:
     * vtkSphereSource ---> vtkPolyDataMapper ---> vtkActor
     */
    // 步骤一：智能指针定义
    vtkSmartPointer<vtkSphereSource> pSphereSource;
    // 步骤二：智能指针实例化
    pSphereSource = vtkSmartPointer<vtkSphereSource>::New();
    // 步骤三：设置球心坐标
    pSphereSource->SetCenter(x, y, z);
    // 步骤三：设置球体的半径
    pSphereSource->SetRadius(r);
    // 步骤四：设置球体的纬度分辨率，即球体纵向的切片数量（垂直/纵向精细度）
    pSphereSource->SetPhiResolution(vNum);
    // 步骤五：设置球体的经度分辨率，即球体横向的切片数量（横向/水平精细度）
    pSphereSource->SetThetaResolution(hNum);

    return pSphereSource;
}

vtkSmartPointer<vtkPolyDataMapper> VTKManager::createPolyDataMapper(vtkSphereSource * pSphereSource)
{
    // 步骤一：智能指针定义
    vtkSmartPointer<vtkPolyDataMapper> pPolyDataMapper;
    // 步骤二：智能指针实例化
    pPolyDataMapper = vtkSmartPointer<vtkPolyDataMapper>::New();
    // 步骤三：设置
    pPolyDataMapper->SetInputConnection(pSphereSource->GetOutputPort());

    return pPolyDataMapper;
}
vtkSmartPointer<vtkActor> VTKManager::createActor(vtkPolyDataMapper *pPolyDataMapper, double r, double g, double b)
{
    // 步骤一：智能指针定义
    vtkSmartPointer<vtkActor> pActor;
    // 步骤二：智能指针实例化
    pActor = vtkSmartPointer<vtkActor>::New();
    // 步骤三：设置映射器
    pActor->SetMapper(pPolyDataMapper);
    // 步骤四：设置颜色
    pActor->GetProperty()->SetColor(r, g, b);

    return pActor;
}

vtkSmartPointer<vtkActor> VTKManager::createActor(vtkPolyDataMapper *pPolyDataMapper, double r, double g, double b, double a)
{
    // 步骤一：智能指针定义
    vtkSmartPointer<vtkActor> pActor;
    // 步骤二：智能指针实例化
    pActor = vtkSmartPointer<vtkActor>::New();
    // 步骤三：设置映射器
    pActor->SetMapper(pPolyDataMapper);
    // 步骤四：设置颜色
    pActor->GetProperty()->SetColor(r, g, b);
    // 步骤五：设置透明度
    pActor->GetProperty()->SetOpacity(a);

    return pActor;
}
vtkSmartPointer<vtkRenderer> VTKManager::createRenderer(vtkActor *pActor)
{
    // 步骤一：智能指针定义
    vtkSmartPointer<vtkRenderer> pRenderer;
    // 步骤二：智能指针实例化
    pRenderer = vtkSmartPointer<vtkRenderer>::New();
    // 步骤三：设置映射器
    pRenderer->AddActor(pActor);

    return pRenderer;
}

vtkSmartPointer<vtkRenderer> VTKManager::createRenderer(std::vector<vtkActor *> listPActor)
{
    // 步骤一：智能指针定义
    vtkSmartPointer<vtkRenderer> pRenderer;
    // 步骤二：智能指针实例化
    pRenderer = vtkSmartPointer<vtkRenderer>::New();
    // 步骤三：设置映射器
    for(int index = 0; index < listPActor.size(); index++)
    {
        pRenderer->AddActor(listPActor.at(index));
    }

    return pRenderer;
}

VTKWidget.cpp

cpp 复制代码

void VTKWidget::test_demo2_1_createSphere()
{
    // 步骤一：创建球体数据源
    vtkSmartPointer<vtkSphereSource> pSphereSource1 =
            VTKManager::createSphereSource(0, 0, 0, 10, 100, 100);
    vtkSmartPointer<vtkSphereSource> pSphereSource2 =
            VTKManager::createSphereSource(-20, 0, 0, 10, 100, 100);
    vtkSmartPointer<vtkSphereSource> pSphereSource3 =
            VTKManager::createSphereSource(20, 0, 0, 10, 100, 100);
    vtkSmartPointer<vtkSphereSource> pSphereSource4 =
            VTKManager::createSphereSource(0, 20, 0, 10, 100, 100);
    vtkSmartPointer<vtkSphereSource> pSphereSource5 =
            VTKManager::createSphereSource(0, -20, 0, 10, 100, 100);
    vtkSmartPointer<vtkSphereSource> pSphereSource6 =
            VTKManager::createSphereSource(0, 0, 20, 10, 100, 100);
    vtkSmartPointer<vtkSphereSource> pSphereSource7 =
            VTKManager::createSphereSource(0, 0, -20, 10, 100, 100);
    // 步骤二：创建多边形映射器
    vtkSmartPointer<vtkPolyDataMapper> pPolyDataMapper1 =
            VTKManager::createPolyDataMapper(pSphereSource1);
    vtkSmartPointer<vtkPolyDataMapper> pPolyDataMapper2 =
            VTKManager::createPolyDataMapper(pSphereSource2);
    vtkSmartPointer<vtkPolyDataMapper> pPolyDataMapper3 =
            VTKManager::createPolyDataMapper(pSphereSource3);
    vtkSmartPointer<vtkPolyDataMapper> pPolyDataMapper4 =
            VTKManager::createPolyDataMapper(pSphereSource4);
    vtkSmartPointer<vtkPolyDataMapper> pPolyDataMapper5 =
            VTKManager::createPolyDataMapper(pSphereSource5);
    vtkSmartPointer<vtkPolyDataMapper> pPolyDataMapper6 =
            VTKManager::createPolyDataMapper(pSphereSource6);
    vtkSmartPointer<vtkPolyDataMapper> pPolyDataMapper7 =
            VTKManager::createPolyDataMapper(pSphereSource7);
    // 步骤三：创建演员
    vtkSmartPointer<vtkActor> pActor1 =
            VTKManager::createActor(pPolyDataMapper1, 1.0, 0.0, 0.0, 0.25);
    vtkSmartPointer<vtkActor> pActor2 =
            VTKManager::createActor(pPolyDataMapper2, 0.0, 1.0, 0.0, 0.25);
    vtkSmartPointer<vtkActor> pActor3 =
            VTKManager::createActor(pPolyDataMapper3, 0.0, 0.0, 1.0, 0.25);
    vtkSmartPointer<vtkActor> pActor4 =
            VTKManager::createActor(pPolyDataMapper4, 1.0, 1.0, 0.0, 0.25);
    vtkSmartPointer<vtkActor> pActor5 =
            VTKManager::createActor(pPolyDataMapper5, 0.0, 1.0, 1.0, 0.25);
    vtkSmartPointer<vtkActor> pActor6 =
            VTKManager::createActor(pPolyDataMapper6, 1.0, 0.0, 1.0, 0.25);
    vtkSmartPointer<vtkActor> pActor7 =
            VTKManager::createActor(pPolyDataMapper7, 1.0, 1.0, 1.0, 0.25);

    // 步骤四：创建渲染器
    std::vector<vtkActor *> listActor;
    listActor.push_back(pActor1);
    listActor.push_back(pActor2);
    listActor.push_back(pActor3);
    listActor.push_back(pActor4);
    listActor.push_back(pActor5);
    listActor.push_back(pActor6);
    listActor.push_back(pActor7);
    vtkSmartPointer<vtkRenderer> pRenderer =
            VTKManager::createRenderer(listActor);

    // 步骤五：渲染器添加到QVTKWidget渲染
    _pQVTKWidget->GetRenderWindow()->AddRenderer(pRenderer);
}

void VTKWidget::test_demo2_2_createSphere()
{
    // 步骤一：创建球体数据源
    vtkSmartPointer<vtkSphereSource> pSphereSource1 =
            VTKManager::createSphereSource(0, 0, 0, 10, 100, 100);
    vtkSmartPointer<vtkSphereSource> pSphereSource2 =
            VTKManager::createSphereSource(-20, 0, 0, 10, 100, 100);
    vtkSmartPointer<vtkSphereSource> pSphereSource3 =
            VTKManager::createSphereSource(20, 0, 0, 10, 100, 100);
    vtkSmartPointer<vtkSphereSource> pSphereSource4 =
            VTKManager::createSphereSource(0, 20, 0, 10, 100, 100);
    vtkSmartPointer<vtkSphereSource> pSphereSource5 =
            VTKManager::createSphereSource(0, -20, 0, 10, 100, 100);
    vtkSmartPointer<vtkSphereSource> pSphereSource6 =
            VTKManager::createSphereSource(0, 0, 20, 10, 100, 100);
    vtkSmartPointer<vtkSphereSource> pSphereSource7 =
            VTKManager::createSphereSource(0, 0, -20, 10, 100, 100);
    // 步骤二：创建多边形映射器
    vtkSmartPointer<vtkPolyDataMapper> pPolyDataMapper1 =
            VTKManager::createPolyDataMapper(pSphereSource1);
    vtkSmartPointer<vtkPolyDataMapper> pPolyDataMapper2 =
            VTKManager::createPolyDataMapper(pSphereSource2);
    vtkSmartPointer<vtkPolyDataMapper> pPolyDataMapper3 =
            VTKManager::createPolyDataMapper(pSphereSource3);
    vtkSmartPointer<vtkPolyDataMapper> pPolyDataMapper4 =
            VTKManager::createPolyDataMapper(pSphereSource4);
    vtkSmartPointer<vtkPolyDataMapper> pPolyDataMapper5 =
            VTKManager::createPolyDataMapper(pSphereSource5);
    vtkSmartPointer<vtkPolyDataMapper> pPolyDataMapper6 =
            VTKManager::createPolyDataMapper(pSphereSource6);
    vtkSmartPointer<vtkPolyDataMapper> pPolyDataMapper7 =
            VTKManager::createPolyDataMapper(pSphereSource7);
    // 步骤三：创建演员
    vtkSmartPointer<vtkActor> pActor1 =
            VTKManager::createActor(pPolyDataMapper1, 1.0, 1.0, 1.0, 0.25);
    vtkSmartPointer<vtkActor> pActor2 =
            VTKManager::createActor(pPolyDataMapper2, 1.0, 1.0, 1.0, 0.25);
    vtkSmartPointer<vtkActor> pActor3 =
            VTKManager::createActor(pPolyDataMapper3, 1.0, 1.0, 1.0, 0.25);
    vtkSmartPointer<vtkActor> pActor4 =
            VTKManager::createActor(pPolyDataMapper4, 1.0, 1.0, 1.0, 0.25);
    vtkSmartPointer<vtkActor> pActor5 =
            VTKManager::createActor(pPolyDataMapper5, 1.0, 1.0, 1.0, 0.25);
    vtkSmartPointer<vtkActor> pActor6 =
            VTKManager::createActor(pPolyDataMapper6, 1.0, 1.0, 1.0, 0.25);
    vtkSmartPointer<vtkActor> pActor7 =
            VTKManager::createActor(pPolyDataMapper7, 1.0, 1.0, 1.0, 0.25);

    // 步骤四：创建渲染器
    std::vector<vtkActor *> listActor;
    listActor.push_back(pActor1);
    listActor.push_back(pActor2);
    listActor.push_back(pActor3);
    listActor.push_back(pActor4);
    listActor.push_back(pActor5);
    listActor.push_back(pActor6);
    listActor.push_back(pActor7);
    vtkSmartPointer<vtkRenderer> pRenderer =
            VTKManager::createRenderer(listActor);

    // 步骤五：渲染器添加到QVTKWidget渲染
    _pQVTKWidget->GetRenderWindow()->AddRenderer(pRenderer);
}

VTK开发笔记（三）：熟悉VTK开发流程，编写球体，多半透明球体Demo

前言

Demo

坐标系

可视化管线渲染流程

智能指针

绘制一个球体

步骤一：创建球体数据源

步骤二：创建多边形映射器

步骤三：创建演员类（类似osg模型结点）

步骤四：创建渲染器

步骤五：设置渲染器到渲染窗口

源码

VTKManager.cpp

VTKWidget.cpp

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