Example: opengl_video_viewport_demo

C++ example source code:

/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2023, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */

#include <mrpt/gui/CDisplayWindow3D.h>
#include <mrpt/hwdrivers/CCameraSensor.h>
#include <mrpt/opengl.h>

#include <chrono>
#include <iostream>
#include <thread>

using namespace std;
using namespace mrpt;
using namespace mrpt::gui;
using namespace mrpt::opengl;
using namespace mrpt::math;
using namespace mrpt::obs;

// ------------------------------------------------------
//              TestOpenGLVideo
// ------------------------------------------------------
void TestOpenGLVideo()
{
    // Show to the user a list of possible camera drivers and creates and open
    // the selected camera.
    cout << "Please, select the input video file or camera...\n";

    mrpt::hwdrivers::CCameraSensor::Ptr cam =
        mrpt::hwdrivers::prepareVideoSourceFromUserSelection();
    if (!cam) return;

    cout << "Video stream open OK\n";

    // Create 3D window:
    CDisplayWindow3D win("#1: Demo of image mode viewport", 320, 240);
    CDisplayWindow3D win2("#2: Demo of image mode viewport", 500, 400);

    // Win #1:
    //  Get the smart pointer to the main viewport object in this window:
    Viewport::Ptr gl_view_main;
    {
        Scene::Ptr& theScene = win.get3DSceneAndLock();
        gl_view_main = theScene->getViewport("main");
        ASSERT_(gl_view_main);
        // IMPORTANT!!! IF NOT UNLOCKED, THE WINDOW WILL NOT BE UPDATED!
        win.unlockAccess3DScene();
    }

    // Win #2:
    //  Get the smart pointer to the main viewport object in this window:
    Viewport::Ptr gl_view_aux;
    {
        Scene::Ptr& theScene = win2.get3DSceneAndLock();
        theScene->insert(mrpt::opengl::CGridPlaneXY::Create());

        // Create small auxiliary viewport
        gl_view_aux = theScene->createViewport("aux");

        gl_view_aux->setViewportPosition(10, 10, 300, 200);
        gl_view_aux->setTransparent(true);

        // IMPORTANT!!! IF NOT UNLOCKED, THE WINDOW WILL NOT BE UPDATED!
        win2.unlockAccess3DScene();
    }

    win.setPos(10, 10);
    win2.setPos(400, 100);

    cout << "Close any window to end.\n";
    while (win.isOpen() && win2.isOpen())
    {
        win.addTextMessage(5, 5, format("%.02fFPS", win.getRenderingFPS()));
        win2.addTextMessage(5, 5, format("%.02fFPS", win2.getRenderingFPS()));
        std::this_thread::sleep_for(1ms);

        // Grab new video frame:
        CObservation::Ptr obs = cam->getNextFrame();
        if (obs)
        {
            if (IS_CLASS(*obs, CObservationImage))
            {
                CObservationImage::Ptr o =
                    std::dynamic_pointer_cast<CObservationImage>(obs);
                win.get3DSceneAndLock();
                gl_view_main->setImageView(o->image);
                win.unlockAccess3DScene();
                win.repaint();

                win2.get3DSceneAndLock();
                gl_view_aux->setImageView(std::move(o->image));
                win2.unlockAccess3DScene();
                win2.repaint();
            }
        }
    }
}

// ------------------------------------------------------
//                      MAIN
// ------------------------------------------------------
int main()
{
    try
    {
        TestOpenGLVideo();

        return 0;
    }
    catch (const std::exception& e)
    {
        std::cerr << "MRPT error: " << mrpt::exception_to_str(e) << std::endl;
        return -1;
    }
}