Example: gui_capture_render_to_img_example

C++ example source code:

/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2024, 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/math/TPose3D.h>
#include <mrpt/opengl/CAxis.h>
#include <mrpt/opengl/CBox.h>
#include <mrpt/opengl/CGridPlaneXY.h>
#include <mrpt/opengl/CSphere.h>
#include <mrpt/system/os.h>

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

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

// ------------------------------------------------------
//              TestDisplay3D
// ------------------------------------------------------
void TestDisplay3D()
{
  CDisplayWindow3D win("Example of 3D Scene Visualization - MRPT", 640, 480);

  Scene::Ptr& theScene = win.get3DSceneAndLock();

  // Add a clone viewport:
  if (true)
  {
    Viewport::Ptr vi = theScene->createViewport("myClone");
    vi->setViewportPosition(0.7, 0.05, 0.28, 0.28);
    vi->setCloneView("main");
    vi->setTransparent(true);
    vi->getCamera().setAzimuthDegrees(45);
    vi->getCamera().setElevationDegrees(45);
    vi->getCamera().setZoomDistance(10);
  }

  // Modify the scene:
  // ------------------------------------------------------
  {
    opengl::CGridPlaneXY::Ptr obj = opengl::CGridPlaneXY::Create(-20, 20, -20, 20, 0, 1);
    obj->setColor(0.4f, 0.4f, 0.4f);
    theScene->insert(obj);
  }

  {
    opengl::CAxis::Ptr obj = opengl::CAxis::Create();
    obj->setFrequency(5);
    obj->enableTickMarks();
    obj->setAxisLimits(-10, -10, -10, 10, 10, 10);
    theScene->insert(obj);
  }

  {
    opengl::CBox::Ptr obj = opengl::CBox::Create();
    obj->setWireframe(false);
    obj->setColor(1, 0, 0);
    obj->setLineWidth(3.0);
    obj->setPose(mrpt::math::TPose3D(10, 0, 0, 0.2, 0.3, 0.1));
    theScene->insert(obj);
  }

  {
    opengl::CSphere::Ptr obj = opengl::CSphere::Create();
    obj->setColor(0, 0, 1);
    obj->setRadius(0.3f);
    obj->setLocation(0, 0, 1);
    obj->setName("ball_1");
    theScene->insert(obj);
  }
  {
    opengl::CSphere::Ptr obj = opengl::CSphere::Create();
    obj->setColor(1, 0, 0);
    obj->setRadius(0.3f);
    obj->setLocation(-1, -1, 1);
    obj->setName("ball_2");
    theScene->insert(obj);
  }

  {
    opengl::CSphere::Ptr obj = opengl::CSphere::Create();
    obj->setColor(0, 1, 0);
    obj->setRadius(0.5);
    obj->setLocation(0, 0, 0);
    obj->setName("USER_MOUSE_PICK");
    theScene->insert(obj);
  }

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

  win.captureImagesStart();

  // Texts:
  win.addTextMessage(0.05, 0.05, "This is a 2D message");

  win.setCameraElevationDeg(25.0f);
  // win.setCameraProjective(false);

  cout << endl;
  cout << "Control with mouse or keyboard. Valid keys:" << endl;
  cout << "  ESC                        -> Exit" << endl;
  cout << "  Left/right cursor arrow    -> Camera azimuth" << endl;
  cout << endl;

  bool end = false;

  mrpt::opengl::TFontParams fp;
  fp.color = mrpt::img::TColorf(0, 0, 1);

  while (!end && win.isOpen())
  {
    // Move the scene:
    Scene::Ptr& scene = win.get3DSceneAndLock();

    auto obj1 = scene->getByName("ball_1");
    const auto p1 = obj1->getPose();
    obj1->setLocation(
        p1.x + cos(p1.y / 2) * 0.05, p1.y - sin(p1.x / 2) * 0.09, p1.z - sin(p1.x / 2) * 0.08);

    auto obj2 = scene->getByName("ball_2");
    const auto p2 = obj2->getPose();
    obj2->setLocation(
        p2.x + cos(p2.y / 2) * 0.05, p2.y - sin(p2.x / 2) * 0.09, p2.z - sin(p2.x / 2) * 0.08);

    win.addTextMessage(
        0.02, 0.98, mrpt::format("ball#1 pos: %s ", p1.translation().asString().c_str()),
        10,  // An arbitrary ID
        fp);

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

    // Update window:
    win.forceRepaint();
    std::this_thread::sleep_for(10ms);

    // Grab frame:
    mrpt::img::CImage::Ptr img = win.getLastWindowImagePtr();
    if (img)
    {
      static int i = 0;
      const string s = format("GRAB_%06i.png", ++i);
      bool savedOk = img->saveToFile(s);
      ASSERT_(savedOk);
      printf("Saved frame image to: %s \r", s.c_str());  // "\ r" is to
                                                         // overwrite the
                                                         // same line over
                                                         // and over
                                                         // again..
    }

    if (mrpt::system::os::kbhit()) end = true;
    if (win.keyHit())
    {
      mrptKeyModifier kmods;
      int key = win.getPushedKey(&kmods);
      printf("Key pushed: %c (%i) - modifiers: 0x%04X\n", char(key), key, kmods);

      if (key == MRPTK_ESCAPE) end = true;

      if (key == MRPTK_RIGHT) win.setCameraAzimuthDeg(win.getCameraAzimuthDeg() + 5);
      if (key == MRPTK_LEFT) win.setCameraAzimuthDeg(win.getCameraAzimuthDeg() - 5);
    }
  };
}

// ------------------------------------------------------
//                      MAIN
// ------------------------------------------------------
int main()
{
  try
  {
    TestDisplay3D();

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