opencv viz module example

opencv在viz有4个例程

Launching Viz
Pose of a widget
Transformations
Creating Widgets

其中前3个比较通用

下面就逐一介绍一下

有些地方写的不太好 我已经修改了代码

1. Launching Viz 

知识点

• Open a visualization window.
• Access a window by its name.
• Start event loop.
• Start event loop for a given amount of time.

#include 
#include 

using namespace cv;
using namespace std;

static void help()
{
    cout
        << "--------------------------------------------------------------------------" << endl
        << "This program shows how to launch a 3D visualization window. You can stop event loop to continue executing. "
        << "You can access the same window via its name. You can run event loop for a given period of time. " << endl
        << "Usage:" << endl
        << "./launching_viz" << endl
        << endl;
}

int main()
{
    help();
    viz::Viz3d myWindow("Viz Demo");

    cout << "This event loop will run until user terminates it by pressing e, E, q, Q." << endl;

    myWindow.spin();
    cout << "First event loop is over" << endl;
    viz::Viz3d sameWindow = viz::getWindowByName("Viz Demo");
    sameWindow.spin();
    cout << "Second event loop is over" << endl;
    sameWindow.spinOnce(1, true);
    while (!sameWindow.wasStopped())
    {
        sameWindow.spinOnce(1, true);
    }
    cout << "Last event loop is over" << endl;
    return 0;
}

这里的注意点是
viz::Viz3d 窗口的关闭 使用按键e,E,q,Q

2. Pose of a widget

知识点

• Add widgets to the visualization window
• Use Affine3 to set pose of a widget
• Rotating and translating a widget along an axis

#include 
// #include 
#include 

using namespace cv;
using namespace std;
static void help()
{
    cout
        << "--------------------------------------------------------------------------" << endl
        << "This program shows how to visualize a cube rotated around (1,1,1) and shifted "
        << "using Rodrigues vector." << endl
        << "Usage:" << endl
        << "./widget_pose" << endl
        << endl;
}
int main()
{
    help();
    viz::Viz3d myWindow("Coordinate Frame");
    myWindow.showWidget("Coordinate Widget", viz::WCoordinateSystem());

    viz::WLine axis(Point3f(-1.0f, -1.0f, -1.0f), Point3f(1.0f, 1.0f, 1.0f));
    axis.setRenderingProperty(viz::LINE_WIDTH, 4.0);
    myWindow.showWidget("Line Widget", axis);

    viz::WCube cube_widget(Point3f(0.5, 0.5, 0.0), Point3f(0.0, 0.0, -0.5), true, viz::Color::blue());
    cube_widget.setRenderingProperty(viz::LINE_WIDTH, 4.0);
    myWindow.showWidget("Cube Widget", cube_widget);

    Mat rot_vec = Mat::zeros(1, 3, CV_32F);
    float translation_phase = 0.0, translation = 0.0;

    while (!myWindow.wasStopped())
    {
        /* Rotation using rodrigues */
        rot_vec.at(0, 0) += CV_PI * 0.01f;
        rot_vec.at(0, 1) += CV_PI * 0.01f;
        rot_vec.at(0, 2) += CV_PI * 0.01f;

        translation_phase += CV_PI * 0.01f;
        translation = sin(translation_phase);

//         Mat rot_mat;
//         Rodrigues(rot_vec, rot_mat);
//         Affine3f pose(rot_mat, Vec3f(translation, translation, translation));

        Affine3f pose(rot_vec, Vec3f(translation, translation, translation));

        myWindow.setWidgetPose("Cube Widget", pose);
        myWindow.spinOnce(1, true);
    }
    return 0;
}

这里我修改了一点

因为这里使用 cv::Affine3f 这个类型作为非齐次的转换矩阵Trasform 3X4 传入到setWidgetPose

由于cv::Affine3f初始化是可以直接使用旋转向量和平移向量的 所以我这里去除了Rodrigues方程 也去除了包含

3. Transformations

知识点

• How to use makeTransformToGlobal to compute pose
• How to use makeCameraPose and Viz3d::setViewerPose
• How to visualize camera position by axes and by viewing frustum

#include 
#include 

using namespace cv;
using namespace std;

static void help()
{
    cout
        << "--------------------------------------------------------------------------" << endl
        << "This program shows how to use makeTransformToGlobal() to compute required pose,"
        << "how to use makeCameraPose and Viz3d::setViewerPose. You can observe the scene "
        << "from camera point of view (C) or global point of view (G)" << endl
        << "Usage:" << endl
        << "./transformations [ G | C ]" << endl
        << endl;
}

int main(int argn, char **argv)
{
    help();

    if (argn < 2)
    {
        cout << "Missing arguments." << endl;
        return 1;
    }

    bool camera_pov = (argv[1][0] == 'C');

    viz::Viz3d myWindow("Coordinate Frame");
    myWindow.showWidget("Coordinate Widget", viz::WCoordinateSystem());

    Vec3f cam_pos(3.0f, 3.0f, 3.0f), cam_focal_point(3.0f, 3.0f, 2.0f), cam_y_dir(-1.0f, 0.0f, 0.0f);

    Affine3f cam_pose = viz::makeCameraPose(cam_pos, cam_focal_point, cam_y_dir);
    Affine3f transform = viz::makeTransformToGlobal(Vec3f(0.0f, -1.0f, 0.0f), Vec3f(-1.0f, 0.0f, 0.0f), Vec3f(0.0f, 0.0f, -1.0f), cam_pos);
    
    Mat bunny_cloud = viz::readCloud("bunny.ply");
    bunny_cloud *= 5.f;
    
    viz::WCloud cloud_widget(bunny_cloud, viz::Color::green());
    Affine3f cloud_pose = Affine3f().translate(Vec3f(0.0f, 0.0f, 3.0f));
    Affine3f cloud_pose_global = transform * cloud_pose;

    if (!camera_pov)
    {
        viz::WCameraPosition cpw(0.5); // Coordinate axes
        viz::WCameraPosition cpw_frustum(Vec2f(0.889484f, 0.523599f)); // Camera frustum
        myWindow.showWidget("CPW", cpw, cam_pose);
        myWindow.showWidget("CPW_FRUSTUM", cpw_frustum, cam_pose);
    }

    myWindow.showWidget("bunny", cloud_widget, cloud_pose_global);
    if (camera_pov)
        myWindow.setViewerPose(cam_pose);
    myWindow.spin();

    return 0;
}

我做了一个小修改

原文中使用了自己写的函数读取点云

我这里使用了原生的 viz::readCloud