Example: opengl_objects_demo

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/maps/COctoMap.h>
#include <mrpt/obs/stock_observations.h>
#include <mrpt/opengl.h>
#include <mrpt/opengl/CPlanarLaserScan.h>
#include <mrpt/random.h>
#include <mrpt/system/filesystem.h>

#include <Eigen/Dense>  // transpose()
#include <chrono>
#include <iostream>
#include <thread>

using namespace std;
using namespace mrpt::literals;  // _deg
using namespace mrpt;  // opengl::
using namespace mrpt::gui;
using namespace mrpt::opengl;
using namespace mrpt::math;
using namespace std::string_literals;

// ------------------------------------------------------
//              TestOpenGLObjects
// ------------------------------------------------------
void TestOpenGLObjects()
{
    mrpt::global_settings::OCTREE_RENDER_MAX_POINTS_PER_NODE(10000);

    CDisplayWindow3D win("Demo of MRPT's OpenGL objects", 640, 480);

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

    auto& rng = mrpt::random::getRandomGenerator();

    // Objects:
    double off_x = 0;
    const double off_y_label = 20;
    const double STEP_X = 25;

    // XY Grid
    {
        // using mrpt smart pointers so that obj survives outside this scope.
        auto obj = opengl::CGridPlaneXY::Create(-7, 7, -7, 7, 0, 1);
        obj->setColor(0.7f, 0.7f, 0.7f);
        obj->setLocation(off_x, 0, 0);
        theScene->insert(obj);

        auto obj2 = opengl::CGridPlaneXY::Create(-9, 9, -9, 9, 0, 2);
        obj2->setColor(0.3f, 0.3f, 0.3f, 0.99f);
        obj2->setLocation(off_x, 20, 0);
        obj2->enableAntiAliasing();
        theScene->insert(obj2);

        auto gl_txt = opengl::CText::Create("CGridPlaneXY");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // XZ Grid
    {
        auto obj = opengl::CGridPlaneXZ::Create(-7, 7, -7, 7, 0, 1);
        obj->setColor(0.7f, 0.7f, 0.7f);
        obj->setLocation(off_x, 0, 0);
        theScene->insert(obj);

        auto gl_txt = opengl::CText::Create("CGridPlaneXZ");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // Arrow
    {
        auto obj = opengl::CArrow::Create(0, 0, 0, 3, 0, 0, 0.2f, 0.1f, 0.2f);
        obj->setLocation(off_x, 0, 0);
        obj->setColor(1, 0, 0);
        obj->setName("arrow #1");
        obj->enableShowName();
        theScene->insert(obj);

        auto obj2 = opengl::CArrow::Create(1, 2, 3, 6, -3, 0, 0.1f, 0.1f, 0.3f);
        obj2->setLocation(off_x, 0, 0);
        obj2->setColor(0, 0, 1);
        theScene->insert(obj2);

        auto gl_txt = opengl::CText::Create("CArrow");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // Axis
    {
        auto obj = opengl::CAxis::Create(-6, -6, -6, 6, 6, 6, 2, 2, true);
        obj->setLocation(off_x, 0, 0);
        theScene->insert(obj);

        auto gl_txt = opengl::CText::Create("CAxis");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // Box
    {
        auto obj = opengl::CBox::Create(
            TPoint3D(0, 0, 0), TPoint3D(1, 1, 1), true, 3.0);
        obj->setLocation(off_x, 0, 0);
        theScene->insert(obj);

        auto obj2 =
            opengl::CBox::Create(TPoint3D(0, 0, 0), TPoint3D(1, 1, 1), false);
        obj2->setLocation(off_x, 4, 0);
        theScene->insert(obj2);

        auto obj3 =
            opengl::CBox::Create(TPoint3D(0, 0, 0), TPoint3D(1, 1, 1), false);
        obj3->enableBoxBorder(true);
        obj3->setLineWidth(3);
        obj3->setColor_u8(0xff, 0x00, 0x00, 0xa0);
        obj3->setLocation(off_x, 8, 0);
        theScene->insert(obj3);

        auto gl_txt = opengl::CText::Create("CBox");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // Frustum
    {
        auto obj = opengl::CFrustum::Create(1, 5, 60, 45, 1.5f, true, false);
        obj->setLocation(off_x, 0, 0);
        theScene->insert(obj);

        auto obj2 = opengl::CFrustum::Create(1, 5, 60, 45, 2.5f, true, true);
        obj2->setLocation(off_x, 6, 0);
        obj2->setColor_u8(0xff, 0x00, 0x00, 0x80);
        theScene->insert(obj2);

        // Default camera params:
        mrpt::img::TCamera c;
        c.nrows = 800;
        c.ncols = 600;
        c.setIntrinsicParamsFromValues(700, 700, 400, 300);

        auto obj3 = opengl::CFrustum::Create(c);
        obj3->setLocation(off_x, 12, 0);
        obj3->setColor_u8(0xff, 0x00, 0x00, 0x80);
        theScene->insert(obj3);

        auto gl_txt = opengl::CText::Create("CFrustum");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // Cylinder
    {
        auto obj = opengl::CCylinder::Create(2, 2, 4, 20);
        obj->setLocation(off_x, 0, 0);
        obj->setColor(0, 0, 0.8f);
        theScene->insert(obj);

        auto obj2 = opengl::CCylinder::Create(2, 1, 4, 20);
        obj2->setLocation(off_x, 6, 0);
        obj2->setColor(0, 0, 0.8f);
        theScene->insert(obj2);

        auto obj3 = opengl::CCylinder::Create(2, 0, 4, 20);
        obj3->setLocation(off_x, -6, 0);
        obj3->setColor(0, 0, 0.8f);
        theScene->insert(obj3);

        auto gl_txt = opengl::CText::Create("CCylinder");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CDisk
    {
        {
            auto obj = opengl::CDisk::Create(2.0f, 1.8f, 50);
            obj->setLocation(off_x, 0, 0);
            obj->setColor(0.8f, 0, 0);
            theScene->insert(obj);
        }

        {
            auto obj = opengl::CDisk::Create(2.0f, 0, 50);
            obj->setLocation(off_x, 5, 0);
            obj->setColor(0.8f, 0, 0);
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("CDisk");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CEllipsoid3D
    {
        const double cov3d_dat[] = {0.9,  0.7,  -0.4, 0.7, 1.6,
                                    -0.6, -0.4, -0.6, 1.5};
        const double cov2d_dat[] = {0.9, 0.7, 0.7, 1.6};
        mrpt::math::CMatrixDouble22 cov2d(cov2d_dat);
        mrpt::math::CMatrixDouble33 cov3d(cov3d_dat);

        {
            auto obj = opengl::CEllipsoid2D::Create();
            obj->setCovMatrix(cov2d);
            obj->setLocation(off_x, 6, 0);
            obj->setQuantiles(2.0);
            theScene->insert(obj);
        }
        {
            auto obj = opengl::CEllipsoid2D::Create();
            obj->setCovMatrix(cov2d);
            obj->setLocation(off_x, 12, 0);
            obj->enableDrawSolid3D(true);
            obj->setQuantiles(2.0);
            theScene->insert(obj);
        }
        {
            auto obj = opengl::CEllipsoid3D::Create();
            obj->setCovMatrix(cov3d);
            obj->setQuantiles(2.0);
            obj->enableDrawSolid3D(false);
            obj->setLocation(off_x, 0, 0);
            theScene->insert(obj);
        }
        {
            auto obj = opengl::CEllipsoid3D::Create();
            obj->setCovMatrix(cov3d);
            obj->setQuantiles(2.0);
            obj->materialShininess(0.99f);
            obj->setName("Ellipsoid shininess=0.99");
            obj->enableShowName();
            obj->enableDrawSolid3D(true);
            obj->setLocation(off_x, -6, 0);
            theScene->insert(obj);
        }
        {
            auto obj = opengl::CEllipsoid3D::Create();
            obj->setCovMatrix(cov3d);
            obj->setQuantiles(2.0);
            obj->materialShininess(0.01f);
            obj->setName("Ellipsoid shininess=0.01");
            obj->enableShowName();
            obj->enableDrawSolid3D(true);
            obj->setLocation(off_x, -12, 0);
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("CEllipsoid3D");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CEllipsoidRangeBearing2D
    {  // (range,bearing) -> (x,y)
        const double cov_params_dat[] = {0.2, 0, 0, 0.1};
        const double mean_params_dat[] = {3.0, 0.5};
        mrpt::math::CMatrixFixed<double, 2, 2> cov_params(cov_params_dat);
        mrpt::math::CMatrixFixed<double, 2, 1> mean_params(mean_params_dat);

        {
            auto obj = opengl::CEllipsoidRangeBearing2D::Create();
            obj->setCovMatrixAndMean(cov_params, mean_params);
            obj->setLocation(off_x, 6, 0);
            obj->setQuantiles(2.0f);
            // obj->setNumberOfSegments(50);
            theScene->insert(obj);

            auto obj_corner = opengl::stock_objects::CornerXYSimple(1, 3);
            obj_corner->setLocation(off_x, 6, 0);
            theScene->insert(obj_corner);
        }
    }
    {  // (range,bearing) -> (x,y)
        const double cov_params_dat[] = {0.2, 0.09, 0.09, 0.1};
        const double mean_params_dat[] = {5.0, -0.5};
        mrpt::math::CMatrixFixed<double, 2, 2> cov_params(cov_params_dat);
        mrpt::math::CMatrixFixed<double, 2, 1> mean_params(mean_params_dat);

        {
            auto obj = opengl::CEllipsoidRangeBearing2D::Create();
            obj->setCovMatrixAndMean(cov_params, mean_params);
            obj->setLocation(off_x, 0, 0);
            obj->setQuantiles(2.0f);
            // obj->setNumberOfSegments(50);
            theScene->insert(obj);

            auto obj_corner = opengl::stock_objects::CornerXYSimple(1, 3);
            obj_corner->setLocation(off_x, 0, 0);
            theScene->insert(obj_corner);
        }

        auto gl_txt = opengl::CText::Create("CEllipsoidRangeBearing2D");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CEllipsoidInverseDepth2D
    {  // (inv_range,yaw) -> (x,y)
        // Formula from our book (ch8) for confidence intervals of 3sigmas:
        const double max_dist = 1e4;
        const double min_dist = 1;
        const double rho_mean = 0.5 * (1. / min_dist + 1. / max_dist);
        const double rho_std = (1. / 6.) * (1. / min_dist - 1. / max_dist);

        const double cov_params_dat[] = {
            square(rho_std), 0, 0, square(2.0_deg)};
        const double mean_params_dat[] = {rho_mean, 70.0_deg};
        mrpt::math::CMatrixFixed<double, 2, 2> cov_params(cov_params_dat);
        mrpt::math::CMatrixFixed<double, 2, 1> mean_params(mean_params_dat);

        {
            auto obj = opengl::CEllipsoidInverseDepth2D::Create();
            obj->setCovMatrixAndMean(cov_params, mean_params);
            obj->setLocation(off_x, 6, 0);
            obj->setQuantiles(3.f);
            obj->setNumberOfSegments(100);
            theScene->insert(obj);

            auto obj_corner = opengl::stock_objects::CornerXYSimple(1, 3);
            obj_corner->setLocation(off_x, 6, 0);
            theScene->insert(obj_corner);
        }

        auto gl_txt = opengl::CText::Create("CEllipsoidInverseDepth2D");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CEllipsoidInverseDepth3D
    {  // (inv_range,yaw,pitch) -> (x,y,z)
        // Formula from our book (ch8) for confidence intervals of 3sigmas:
        const double max_dist = 1e2;
        const double min_dist = 1;
        const double rho_mean = 0.5 * (1. / min_dist + 1. / max_dist);
        const double rho_std = (1. / 6.) * (1. / min_dist - 1. / max_dist);

        const double cov_params_dat[] = {square(rho_std), 0, 0, 0,
                                         square(2.0_deg), 0, 0, 0,
                                         square(2.0_deg)};
        const double mean_params_dat[] = {rho_mean, 30.0_deg, -45.0_deg};
        mrpt::math::CMatrixFixed<double, 3, 3> cov_params(cov_params_dat);
        mrpt::math::CMatrixFixed<double, 3, 1> mean_params(mean_params_dat);

        {
            auto obj = opengl::CEllipsoidInverseDepth3D::Create();
            obj->setCovMatrixAndMean(cov_params, mean_params);
            obj->setLocation(off_x, 0, 0);
            obj->setQuantiles(3.f);
            // obj->setNumberOfSegments(50);
            theScene->insert(obj);

            auto obj_corner = opengl::stock_objects::CornerXYZSimple(1, 3);
            obj_corner->setLocation(off_x, 0, 0);
            theScene->insert(obj_corner);
        }

        auto gl_txt = opengl::CText::Create("CEllipsoidInverseDepth3D");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CMesh3D
    {
        auto obj = opengl::CMesh3D::Create();
        obj->enableShowEdges(false);
        obj->enableShowFaces(true);
        obj->enableShowVertices(false);
        obj->setLocation(off_x, 0, 0);

        const unsigned int rows = 200, cols = 200;
        const unsigned int num_verts = (rows + 1) * (cols + 1);
        const unsigned int num_faces = rows * cols;
        int* vert_per_face = new int[num_faces];
        int* face_verts = new int[4 * num_faces];
        float* vert_coords = new float[3 * num_verts];

        // Assign vertices to faces and set them to be Quads
        unsigned int first_ind = 0;
        for (unsigned int u = 0; u < cols; u++)
        {
            for (unsigned int v = 0; v < rows; v++)
            {
                const unsigned int face_ind = v + u * rows;
                vert_per_face[face_ind] = 4;

                face_verts[4 * face_ind] = first_ind;
                face_verts[4 * face_ind + 1] = first_ind + 1;
                face_verts[4 * face_ind + 2] = first_ind + rows + 2;
                face_verts[4 * face_ind + 3] = first_ind + rows + 1;
                first_ind++;
            }

            first_ind++;
        }

        // Create vert coords
        for (unsigned int u = 0; u <= cols; u++)
            for (unsigned int v = 0; v <= rows; v++)
            {
                const unsigned int vert_ind = v + u * (rows + 1);

                vert_coords[3 * vert_ind] = (2.f - 0.01f * u) *
                    (2.f + cos(0.01f * M_PI * v)) * cos(0.01f * M_PI * u);
                vert_coords[3 * vert_ind + 1] = (2.f - 0.01f * u) *
                    (2.f + cos(0.01f * M_PI * v)) * sin(0.01f * M_PI * u);
                vert_coords[3 * vert_ind + 2] =
                    3.f * 0.01f * u + (2.f - 0.01f * u) * sin(0.01f * M_PI * v);
            }

        obj->loadMesh(
            num_verts, num_faces, vert_per_face, face_verts, vert_coords);
        theScene->insert(obj);

        auto gl_txt = opengl::CText::Create("CMesh3D");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CMeshFast, CMesh:
    {
        opengl::CMeshFast::Ptr obj1 = opengl::CMeshFast::Create();
        opengl::CMeshFast::Ptr obj2 = opengl::CMeshFast::Create();
        opengl::CMesh::Ptr obj3 = opengl::CMesh::Create();
        opengl::CMesh::Ptr obj4 = opengl::CMesh::Create();
        opengl::CMesh::Ptr obj5 = opengl::CMesh::Create();

        obj1->setXBounds(-1, 1);
        obj1->setYBounds(-1, 1);

        const int W = 128, H = 128;

        mrpt::math::CMatrixDynamic<float> Z(H, W);

        for (int r = 0; r < H; r++)
            for (int c = 0; c < W; c++)
                Z(r, c) = sin(0.05 * (c + r) - 0.5) * cos(0.9 - 0.03 * r);

        const std::string texture_file = mrpt::system::getShareMRPTDir() +
            "datasets/sample-texture-terrain.jpg"s;

        const std::string texture_file2 = mrpt::system::getShareMRPTDir() +
            "datasets/sample-texture-corners.jpg"s;

        mrpt::img::CImage im, im2;

        // obj1:
        obj1->setZ(Z);
        obj1->enableColorFromZ(true);
        obj1->setPointSize(2.0);
        obj1->setLocation(off_x, 0, 0);
        theScene->insert(obj1);

        // obj 2:
        if (im.loadFromFile(texture_file))
        {
            obj2->assignImageAndZ(im, Z);
            obj2->setPointSize(2.0);
            obj2->setLocation(off_x, 3, 0);
            theScene->insert(obj2);
        }
        {
            auto gl_txt = opengl::CText::Create("CMeshFast");
            gl_txt->setLocation(off_x, off_y_label, 0);
            theScene->insert(gl_txt);
        }

        off_x += STEP_X;

        // obj 3:
        obj3->setZ(Z);
        obj3->enableColorFromZ(true, mrpt::img::cmJET);
        obj3->enableWireFrame(true);
        obj3->setLocation(off_x, 0, 0);
        obj3->cullFaces(mrpt::opengl::TCullFace::BACK);
        // obj3->enableTextureMipMap(false);
        theScene->insert(obj3);

        // obj 4:
        if (im.getWidth() > 1)
        {
            obj4->assignImageAndZ(im, Z);
            obj4->setLocation(off_x, 3, 0);
            obj4->cullFaces(mrpt::opengl::TCullFace::BACK);
            // obj4->enableTextureMipMap(false);
            theScene->insert(obj4);
        }
        // obj 5:
        if (im.getWidth() > 1)
        {
            obj5->assignImageAndZ(im, Z);
            obj5->setMeshTextureExtension(0.25, 0.5);
            obj5->setLocation(off_x + 3, 3, 0);
            // obj5->enableTextureMipMap(false);
            theScene->insert(obj5);
        }

        mrpt::math::CMatrixDynamic<float> Z2(H, W);

        if (im2.loadFromFile(texture_file2))
        {
            im2.getAsMatrix(Z2);

            opengl::CMesh::Ptr obj = opengl::CMesh::Create(
                false /*transparency*/,  //
                -1, 1,  // x: Min Max
                1, -1  // y: Min Max
            );
            obj->assignImageAndZ(im2, Z2);
            obj->setLocation(off_x, 6, 0);
            theScene->insert(obj);
        }
        if (im2.loadFromFile(texture_file2))
        {
            opengl::CMesh::Ptr obj = opengl::CMesh::Create(
                false /*transparency*/,  //
                1, -1,  // x: Min Max
                -1, 1  // y: Min Max
            );
            obj->assignImageAndZ(im2, Z2);
            obj->setLocation(off_x, 9, 0);
            theScene->insert(obj);
        }

        {
            auto gl_txt = opengl::CText::Create("CMesh");
            gl_txt->setLocation(off_x, off_y_label, 0);
            theScene->insert(gl_txt);
        }
    }
    off_x += STEP_X;

    // CPointCloud
    {
        auto obj = opengl::CPointCloud::Create();
        obj->setLocation(off_x, 0, 0);
        theScene->insert(obj);

        obj->setPointSize(1.0);
        obj->enableColorFromY();

        for (int i = 0; i < 100000; i++)
            obj->insertPoint(
                rng.drawUniform<float>(-5, 5), rng.drawUniform<float>(-5, 5),
                rng.drawUniform<float>(-5, 5));

        auto gl_txt = opengl::CText::Create("CPointCloud");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CPointCloudColoured
    {
        auto obj = opengl::CPointCloudColoured::Create();
        obj->setLocation(off_x, 0, 0);
        theScene->insert(obj);

        obj->setPointSize(1.0);

        for (int i = 0; i < 200; i++)
            obj->push_back(
                rng.drawUniform<float>(-5, 5), rng.drawUniform<float>(-5, 5),
                rng.drawUniform<float>(-5, 5), rng.drawUniform<float>(0, 1),
                rng.drawUniform<float>(0, 1), rng.drawUniform<float>(0, 1));

        auto gl_txt = opengl::CText::Create("CPointCloudColoured");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CPolyhedron
    {
        {
            auto obj = opengl::CPolyhedron::CreateCuboctahedron(1.0);
            obj->setLocation(off_x, 0, 0);
            obj->setWireframe(true);
            theScene->insert(obj);
        }
        {
            auto obj = opengl::CPolyhedron::CreateDodecahedron(1.0);
            obj->setLocation(off_x, -5, 0);
            theScene->insert(obj);
        }
        {
            auto obj = opengl::CPolyhedron::CreateIcosahedron(1.0);
            obj->setLocation(off_x, 5, 0);
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("CPolyhedron");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CSphere
    {
        {
            auto obj = opengl::CSphere::Create(3.0);
            obj->setLocation(off_x, 0, 0);
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("CSphere");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CText
    {
        {
            auto obj = opengl::CText::Create(
                "This is a CText example! My size is invariant to "
                "eye-distance");
            obj->setLocation(off_x, 0, 0);
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("CText");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CText3D
    {
        {
            auto obj = opengl::CText3D::Create("I'm a cool CText3D!");
            obj->setLocation(off_x, 0, 0);
            theScene->insert(obj);
        }

        {
            auto obj = opengl::CText3D::Create("A rotated CText3D");
            obj->setPose(
                mrpt::poses::CPose3D(off_x, 0, 0, 0, 0, 0) +
                mrpt::poses::CPose3D::FromString("[0 5 0 180 0 90]"));
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("CText3D");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CColorMap
    {
        {
            auto obj = opengl::CColorBar::Create(
                mrpt::img::cmHOT, 0.2, 1.0, 0.0, 1.0, -50.0, 100.0,
                "%7.02f m/s");
            obj->setLocation(off_x, 0, 0);
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("CColorBar");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CSetOfLines
    {
        for (int rep = 0; rep < 2; rep++)
        {
            auto obj = opengl::CSetOfLines::Create();
            obj->setLocation(off_x, rep * 20, 0);

            for (int i = 0; i < 15; i++)
                obj->appendLine(
                    rng.drawUniform(-5, 5), rng.drawUniform(-5, 5),
                    rng.drawUniform(-5, 5), rng.drawUniform(-5, 5),
                    rng.drawUniform(-5, 5), rng.drawUniform(-5, 5));

            if (rep == 1) obj->setVerticesPointSize(5.0f);
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("CSetOfLines");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CSimpleLine
    {
        {
            auto obj = opengl::CSimpleLine::Create();
            obj->setLocation(off_x, 0, 0);

            obj->setLineCoords(
                rng.drawUniform<float>(-5, 5), rng.drawUniform<float>(-5, 5),
                rng.drawUniform<float>(-5, 5), rng.drawUniform<float>(-5, 5),
                rng.drawUniform<float>(-5, 5), rng.drawUniform<float>(-5, 5));

            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("CSimpleLine");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CVectorField2D
    {
        {
            auto obj = opengl::CVectorField2D::Create();
            obj->setLocation(off_x, 0, 0);

            CMatrixFloat x(16, 16), y(16, 16);
            for (int i = 0; i < x.rows(); i++)
                for (int j = 0; j < x.cols(); j++)
                {
                    x(i, j) = sin(0.3 * i);
                    y(i, j) = cos(0.3 * i);
                }
            obj->setVectorField(x, y);
            obj->setPointColor(1, 0.3f, 0);
            obj->setVectorFieldColor(0, 0, 1);
            obj->setPointSize(3.0);
            obj->setLineWidth(2.0);
            obj->setGridCenterAndCellSize(0, 0, 1.2f, 1.2f);
            obj->adjustVectorFieldToGrid();
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("CVectorField2D");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CVectorField3D
    {
        {
            const unsigned int num = 20;
            const float scale = 0.8 * STEP_X / num;
            auto obj = opengl::CVectorField3D::Create();
            obj->setLocation(off_x, -0.5 * scale * num, 0);  //

            CMatrixFloat x(num, num), y(num, num), z(num, num);
            CMatrixFloat vx(num, num), vy(num, num), vz(num, num);
            for (int i = 0; i < x.rows(); i++)
                for (int j = 0; j < x.cols(); j++)
                {
                    x(i, j) = (i - 0.5 * num) * scale;
                    y(i, j) = j * scale;
                    z(i, j) = 3 * sin(0.3 * i) * cos(0.3 * j);
                    vx(i, j) = 0.4 * sin(0.3 * i);
                    vy(i, j) = 0.8 * cos(0.3 * i);
                    vz(i, j) = 0.01 * i * j;
                }
            obj->setPointCoordinates(x, y, z);
            obj->setVectorField(vx, vy, vz);
            obj->setPointColor(1, 0.3f, 0);
            obj->setVectorFieldColor(0, 0, 1);
            obj->setPointSize(3.0);
            obj->setLineWidth(2.0);
            obj->enableColorFromModule();
            obj->setMaxSpeedForColor(3.0);
            obj->setMotionFieldColormap(0, 0, 1, 1, 0, 0);
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("CVectorField3D");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // stock_objects::BumblebeeCamera
    {
        {
            auto obj = opengl::stock_objects::BumblebeeCamera();
            obj->setLocation(off_x, 0, 0);
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("stock_objects::BumblebeeCamera()");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // stock_objects::CornerXYSimple
    {
        {
            auto obj = opengl::stock_objects::CornerXYSimple(1, 3);
            obj->setLocation(off_x, 0, 0);
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("stock_objects::CornerXYSimple()");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // stock_objects::CornerXYZSimple
    {
        {
            auto obj = opengl::stock_objects::CornerXYZSimple(1, 3);
            obj->setLocation(off_x, 0, 0);
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("stock_objects::CornerXYZSimple()");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // stock_objects::CornerXYZ
    {
        {
            auto obj = opengl::stock_objects::CornerXYZ();
            obj->setLocation(off_x, 0, 0);
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("stock_objects::CornerXYZ()");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CSetOfTriangles: tested via stock_objects:
    // stock_objects::RobotPioneer
    {
        {
            auto obj = opengl::stock_objects::RobotPioneer();
            obj->setLocation(off_x, 0, 0);
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("stock_objects::RobotPioneer()");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // stock_objects::Hokuyo_URG
    {
        {
            auto obj = opengl::stock_objects::Hokuyo_URG();
            obj->setLocation(off_x, 0, 0);
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("stock_objects::Hokuyo_URG()");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // stock_objects::Hokuyo_UTM
    {
        {
            auto obj = opengl::stock_objects::Hokuyo_UTM();
            obj->setLocation(off_x, 0, 0);
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("stock_objects::Hokuyo_UTM()");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // stock_objects::Househam_Sprayer
    {
        {
            auto obj = opengl::stock_objects::Househam_Sprayer();
            obj->setLocation(off_x, 0, 0);
            theScene->insert(obj);
        }

        auto gl_txt =
            opengl::CText::Create("stock_objects::Househam_Sprayer()");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // stock_objects::RobotRhodon
    {
        {
            auto obj = opengl::stock_objects::RobotRhodon();
            obj->setLocation(off_x, 0, 0);
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("stock_objects::RobotRhodon()");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CPlanarLaserScan
    {
        auto obj = mrpt::opengl::CPlanarLaserScan::Create();
        obj->setPose(mrpt::poses::CPose3D(off_x, 0, 0, 90.0_deg, 0, 0));

        mrpt::obs::CObservation2DRangeScan scan;
        mrpt::obs::stock_observations::example2DRangeScan(scan);

        obj->setScan(scan);

        theScene->insert(obj);

        auto gl_txt = opengl::CText::Create("CPlanarLaserScan");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // CTexturedPlane
    {
        mrpt::img::CImage pic, picAlpha;
        const size_t W = 256, H = 256;
        pic.resize(W, H, mrpt::img::CH_RGB);
        picAlpha.resize(W, H, mrpt::img::CH_GRAY);
        pic.filledRectangle(0, 0, W - 1, H - 1, mrpt::img::TColor::black());
        pic.filledRectangle(0, 0, W / 4, H / 2, mrpt::img::TColor::white());

        picAlpha.filledRectangle(
            0, 0, W - 1, H - 1, mrpt::img::TColor(0x55, 0x55, 0x55));
        picAlpha.filledRectangle(
            0, 0, W / 4, H / 2, mrpt::img::TColor(0xa0, 0xa0, 0xa0));

        {
            opengl::CTexturedPlane::Ptr obj = opengl::CTexturedPlane::Create();
            obj->setPose(mrpt::poses::CPose3D(off_x, 0, 0, 0, 90.0_deg, 0));
            obj->assignImage(pic);
            theScene->insert(obj);
        }

        {
            opengl::CTexturedPlane::Ptr obj = opengl::CTexturedPlane::Create();
            obj->setPose(mrpt::poses::CPose3D(off_x, 4.0, 0, 0, 90.0_deg, 0));
            obj->assignImage(pic, picAlpha);
            theScene->insert(obj);
        }

        // a plane w/o a texture is a plain color plane:
        {
            opengl::CTexturedPlane::Ptr obj = opengl::CTexturedPlane::Create();
            obj->setPose(mrpt::poses::CPose3D(off_x, 8.0, 0, 0, 90.0_deg, 0));
            obj->setColor_u8(0xff, 0x00, 0x00, 0xff);
            theScene->insert(obj);
        }
        {
            opengl::CTexturedPlane::Ptr obj = opengl::CTexturedPlane::Create();
            obj->setPose(mrpt::poses::CPose3D(off_x, 12.0, 0, 0, 90.0_deg, 0));
            obj->setColor_u8(0xff, 0x00, 0x00, 0x40);
            theScene->insert(obj);
        }

        {
            opengl::CTexturedPlane::Ptr obj = opengl::CTexturedPlane::Create();
            obj->setPose(mrpt::poses::CPose3D(off_x, 6.0, -3.0, 0, 0.0_deg, 0));
            obj->assignImage(pic);
            obj->enableLighting(true);
            theScene->insert(obj);
        }
        {
            opengl::CTexturedPlane::Ptr obj = opengl::CTexturedPlane::Create();
            obj->setPose(mrpt::poses::CPose3D(off_x, 3.9, -3.0, 0, 0.0_deg, 0));
            obj->setColor_u8(0xff, 0x00, 0x00, 0xff);
            obj->enableLighting(true);
            theScene->insert(obj);
        }

        auto gl_txt = opengl::CText::Create("CTexturedPlane");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // COctoMapVoxels
    {
        mrpt::maps::COctoMap map(0.2);
        // Insert 2D scan:

        mrpt::obs::CObservation2DRangeScan scan1;
        mrpt::obs::stock_observations::example2DRangeScan(scan1);
        map.insertObservation(scan1);

        auto gl_map1 = mrpt::opengl::COctoMapVoxels::Create();
        auto gl_map2 = mrpt::opengl::COctoMapVoxels::Create();
        auto gl_map3 = mrpt::opengl::COctoMapVoxels::Create();

        map.getAsOctoMapVoxels(*gl_map1);

        map.getAsOctoMapVoxels(*gl_map2);

        // map.renderingOptions.generateGridLines = true;
        map.getAsOctoMapVoxels(*gl_map3);

        gl_map1->showGridLines(false);
        gl_map1->showVoxelsAsPoints(true);
        gl_map1->setPointSize(3.0);
        gl_map1->setLocation(off_x, 0, 0);
        theScene->insert(gl_map1);

        gl_map2->showVoxelsAsPoints(false);
        gl_map2->showVoxels(VOXEL_SET_OCCUPIED, true);
        gl_map2->showVoxels(VOXEL_SET_FREESPACE, true);
        gl_map2->setLocation(off_x, 4, 0);
        theScene->insert(gl_map2);

        gl_map3->showVoxelsAsPoints(true);
        gl_map3->showGridLines(true);
        gl_map3->setLocation(off_x, 8, 0);
        theScene->insert(gl_map3);

        auto gl_txt = opengl::CText::Create("COctoMapVoxels");
        gl_txt->setLocation(off_x, off_y_label, 0);
        theScene->insert(gl_txt);
    }
    off_x += STEP_X;

    // ground plane (to test shadows):
    // A plane w/o a texture is a plain color plane:
    {
        auto obj = mrpt::opengl::CBox::Create();
        obj->setColor_u8(0xa0, 0xa0, 0xa0, 0xff);
        obj->setLocation(0, 0, -5.0f);
        obj->setBoxCorners({-20.0f, -20.0f, .0f}, {off_x + 20.f, 40.0f, -0.1f});
        obj->cullFaces(TCullFace::BACK);  // avoid z-fighting
        theScene->insert(obj);
    }

    // Arrow to show the light direction:
    auto glLightArrow = opengl::CArrow::Create(
        mrpt::math::TPoint3Df(0, 0, 0), mrpt::math::TPoint3Df(1, 0, 0));
    glLightArrow->setLocation(off_x / 5, -4.0, 5.0);
    glLightArrow->setColor(0, 1, 0);
    glLightArrow->setName("Light dir.");
    glLightArrow->enableShowName();
    theScene->insert(glLightArrow);

    // Add image-mode viewport:
    {
        const std::string img_file = mrpt::system::getShareMRPTDir() +
            "datasets/stereo-calib/0_left.jpg"s;

        mrpt::img::CImage im;
        if (im.loadFromFile(img_file))
        {
            auto glView = theScene->createViewport("image1");
            glView->setViewportPosition(0.7, 0, 0.3, 0.3);
            glView->setImageView(im);

            glView->setBorderSize(1);
        }
    }

    // Zoom out:
    win.setCameraZoom(250);

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

    cout << "Close the window to end.\n";

    mrpt::opengl::TFontParams fp;
    fp.vfont_scale = 14;  // pixels
    fp.draw_shadow = true;
    win.addTextMessage(5, 5, "", 0 /*id*/, fp);

    auto viewport = theScene->getViewport();

    mrpt::opengl::TLightParameters& lights = viewport->lightParameters();

    lights.ambient = 0.2;

    while (win.isOpen())
    {
        // Lights:
        const double t = mrpt::Clock::nowDouble();
        const auto p = glLightArrow->getPose();

        const auto lightDir = mrpt::poses::CPose3D::FromXYZYawPitchRoll(
            p.x, p.y, p.z, t * 10.0_deg, 45.0_deg, 0.0_deg);

        glLightArrow->setPose(lightDir);

        lights.direction =
            lightDir.getRotationMatrix().extractColumn<mrpt::math::TVector3Df>(
                0);

        if (win.keyHit())
        {
            switch (win.getPushedKey())
            {
                case 'S':
                case 's':
                    // toggle shadows:
                    viewport->enableShadowCasting(
                        !viewport->isShadowCastingEnabled());
                    break;
            };
        }

        win.updateTextMessage(
            0 /*id*/,
            format(
                "Render time=%.03fms | Shadows: %s",
                1e3 / win.getRenderingFPS(),
                viewport->isShadowCastingEnabled() ? "On" : "Off"));
        std::this_thread::sleep_for(2ms);
        win.repaint();
    }
}

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

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