Example: opengl_octree_render_huge_pointcloud

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/img/TColor.h>
#include <mrpt/math/geometry.h>
#include <mrpt/opengl/CPointCloud.h>
#include <mrpt/random.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::img;

void insertRandomPoints_uniform(
    const size_t N, opengl::CPointCloud::Ptr& gl, const TPoint3D& p_min,
    const TPoint3D& p_max)
{
    auto& rnd = random::getRandomGenerator();
    for (size_t i = 0; i < N; i++)
        gl->insertPoint(
            rnd.drawUniform<float>(p_min.x, p_max.x),
            rnd.drawUniform<float>(p_min.y, p_max.y),
            rnd.drawUniform<float>(p_min.z, p_max.z));
}

void insertRandomPoints_screw(
    const size_t N, opengl::CPointCloud::Ptr& gl, const TPoint3D& p_start,
    const TPoint3D& p_end)
{
    TPoint3D d = p_end - p_start;
    d *= 1.0 / N;

    TPoint3D up(0, 0, 1);
    TPoint3D lat;
    mrpt::math::crossProduct3D(d, up, lat);
    lat *= 1.0 / lat.norm();

    TPoint3D p = p_start;
    for (size_t i = 0; i < N; i++)
    {
        const double ang = i * 0.01;
        TPoint3D pp = p + up * 30 * cos(ang) + lat * 30 * sin(ang);
        const auto ppf = TPoint3Df(pp);
        gl->insertPoint(ppf.x, ppf.y, ppf.z);
        p += d;
    }
}

void insertRandomPoints_gauss(
    const size_t N, opengl::CPointCloud::Ptr& gl, const TPoint3D& p_mean,
    const TPoint3D& p_stddevs)
{
    auto& rnd = random::getRandomGenerator();
    for (size_t i = 0; i < N; i++)
        gl->insertPoint(
            rnd.drawGaussian1D<float>(p_mean.x, p_stddevs.x),
            rnd.drawGaussian1D<float>(p_mean.y, p_stddevs.y),
            rnd.drawGaussian1D<float>(p_mean.z, p_stddevs.z));
}

// ------------------------------------------------------
//              TestOctreeRenderHugePointCloud
// ------------------------------------------------------
void TestOctreeRenderHugePointCloud()
{
    // Change this in your program as needed:
    // mrpt::global_settings::OCTREE_RENDER_MAX_DENSITY_POINTS_PER_SQPIXEL(0.1f);

    CDisplayWindow3D win("Demo of MRPT's octree pointclouds", 640, 480);

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

    // CPointCloud
    opengl::CPointCloud::Ptr gl_pointcloud = opengl::CPointCloud::Create();
    theScene->insert(gl_pointcloud);

    gl_pointcloud->setPointSize(3.0);
    gl_pointcloud->enableColorFromZ();

    // Set the list of all points:

    const double L = 1e3;

    cout << "Building point cloud...";
    cout.flush();

    for (int XX = -10; XX <= 10; XX++)
    {
        const double off_x = XX * 2 * L;

        for (int YY = -10; YY <= 10; YY++)
        {
            const double off_y = YY * 2 * L;

            insertRandomPoints_screw(
                1e4, gl_pointcloud, TPoint3D(off_x + 0, off_y + 0, 0),
                TPoint3D(off_x + L, off_y + 0, 500));

            insertRandomPoints_screw(
                1e4, gl_pointcloud, TPoint3D(off_x + L, off_y + 0, 500),
                TPoint3D(off_x + L, off_y + L, -500));

            insertRandomPoints_screw(
                1e4, gl_pointcloud, TPoint3D(off_x + L, off_y + L, -500),
                TPoint3D(off_x + 0, off_y + L, 500));

            insertRandomPoints_screw(
                1e4, gl_pointcloud, TPoint3D(off_x + 0, off_y + L, 500),
                TPoint3D(off_x + 0, off_y + 0, 0));
        }
    }

    cout << "Done.\n";
    cout.flush();

    printf("Point count: %e\n", (double)gl_pointcloud->size());

    // Draw the octree bounding boxes:
    mrpt::opengl::CSetOfObjects::Ptr gl_bb =
        mrpt::opengl::CSetOfObjects::Create();
    gl_pointcloud->octree_get_graphics_boundingboxes(*gl_bb);
    theScene->insert(gl_bb);

    // gl_pointcloud->octree_debug_dump_tree(std::cout);

    win.setCameraZoom(600);
    {
        mrpt::opengl::Viewport::Ptr view = theScene->getViewport("main");
        view->setViewportClipDistances(0.1f, 1e6f);
    }

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

    cout << "Close the window or press any key to end.\n";
    bool end = false;
    while (win.isOpen() && !end)
    {
        std::this_thread::sleep_for(5ms);

        if (win.keyHit())
        {
            switch (win.getPushedKey())
            {
                case 'q': end = true; break;
                case 'b': gl_bb->setVisibility(!gl_bb->isVisible()); break;
            };
        }

        // Update the texts on the gl display:
        string s = mrpt::format(
            "FPS=%5.02f | Rendered points=%.02e/%.02e (%.02f%%) | "
            "Visib.oct.nodes: %u/%u",
            win.getRenderingFPS(), (double)gl_pointcloud->getActuallyRendered(),
            (double)gl_pointcloud->size(),
            100 * double(gl_pointcloud->getActuallyRendered()) /
                double(gl_pointcloud->size()),
            (unsigned int)gl_pointcloud->octree_get_visible_nodes(),
            (unsigned int)gl_pointcloud->octree_get_node_count());

        win.get3DSceneAndLock();
        win.addTextMessage(5, 5, s, 0);
        win.addTextMessage(
            5, 35, "'b': switch bounding-boxes visible, 'q': quit", 1);
        win.unlockAccess3DScene();
        win.repaint();
    }
}

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

        std::this_thread::sleep_for(500ms);

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