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 <opencv2/viz.hpp>#include <iostream>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 <opencv2/viz.hpp>// #include <opencv2/calib3d.hpp>#include <iostream>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<float>(0, 0) += CV_PI * 0.01f;        rot_vec.at<float>(0, 1) += CV_PI * 0.01f;        rot_vec.at<float>(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<opencv2/calib3d.hpp>

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 <opencv2/viz.hpp>#include <iostream>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