Example: math_ransac_plane3d_example2

This example shows how to use MRPT’s RANSAC C++ template to detect planes from a 3D point cloud given as a mrpt::maps::CPointsMap.

See also the RANSAC tutorial page.

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/CSimplePointsMap.h>
#include <mrpt/math/ransac.h>
#include <mrpt/opengl/CGridPlaneXY.h>
#include <mrpt/opengl/CPointCloud.h>
#include <mrpt/opengl/CTexturedPlane.h>
#include <mrpt/opengl/stock_objects.h>
#include <mrpt/poses/CPose3D.h>
#include <mrpt/random.h>
#include <mrpt/system/CTicTac.h>

#include <iostream>

using namespace mrpt;
using namespace mrpt::gui;
using namespace mrpt::math;
using namespace mrpt::random;
using namespace mrpt::poses;
using namespace mrpt::system;
using namespace std;

// Define as needed for your application:
using MyRansac = mrpt::math::RANSAC_Template<
    float,                   // Numeric data type: float since pointclouds use float
    mrpt::maps::CPointsMap,  // Dataset type (can be an abstract base
                             // type)
    mrpt::math::TPlane       // Model type to be estimated
    >;

namespace mrpt::math
{
// Overload for your custom dataset type:
size_t ransacDatasetSize(const mrpt::maps::CPointsMap& dataset) { return dataset.size(); }
}  // namespace mrpt::math

void ransac3Dplane_fit(
    const mrpt::maps::CPointsMap& allData,
    const std::vector<size_t>& useIndices,
    vector<mrpt::math::TPlane>& fitModels)
{
  ASSERT_(useIndices.size() == 3);

  TPoint3D pt[3];
  for (int i = 0; i < 3; i++) allData.getPoint(useIndices[i], pt[i]);

  try
  {
    fitModels.resize(1);
    fitModels[0] = TPlane(pt[0], pt[1], pt[2]);
  }
  catch (exception&)
  {
    // If the three points are degenerated, an exception may be thrown in
    // the plane ctor
    fitModels.clear();
    return;
  }
}

void ransac3Dplane_distance(
    const mrpt::maps::CPointsMap& allData,
    const vector<mrpt::math::TPlane>& testModels,
    const double distanceThreshold,
    unsigned int& out_bestModelIndex,
    std::vector<size_t>& out_inlierIndices)
{
  ASSERT_(testModels.size() == 1);
  out_bestModelIndex = 0;
  const mrpt::math::TPlane& plane = testModels[0];

  const size_t N = allData.size();
  out_inlierIndices.clear();
  out_inlierIndices.reserve(100);
  for (size_t i = 0; i < N; i++)
  {
    mrpt::math::TPoint3D pt;
    allData.getPoint(i, pt);
    const double d = plane.distance(pt);
    if (d < distanceThreshold) out_inlierIndices.push_back(i);
  }
}

bool ransac3Dplane_degenerate(
    const mrpt::maps::CPointsMap& allData, const std::vector<size_t>& useIndices)
{
  return false;
}

// ------------------------------------------------------
//              TestRANSAC
// ------------------------------------------------------
void TestRANSAC()
{
  auto& rng = getRandomGenerator();
  rng.randomize();

  // Generate random points:
  // ------------------------------------
  const size_t N_plane = 300;
  const size_t N_noise = 100;

  const double PLANE_EQ[4] = {1, -1, 1, -2};

  mrpt::maps::CSimplePointsMap data;
  data.reserve(N_plane + N_noise);

  for (size_t i = 0; i < N_plane; i++)
  {
    const double xx = rng.drawUniform(-3, 3);
    const double yy = rng.drawUniform(-3, 3);
    const double zz = -(PLANE_EQ[3] + PLANE_EQ[0] * xx + PLANE_EQ[1] * yy) / PLANE_EQ[2];
    data.insertPointFast(xx, yy, zz);
  }

  for (size_t i = 0; i < N_noise; i++)
  {
    data.insertPointFast(rng.drawUniform(-4, 4), rng.drawUniform(-4, 4), rng.drawUniform(-4, 4));
  }

  // Run RANSAC
  // ------------------------------------
  mrpt::math::TPlane best_model;
  std::vector<size_t> best_inliers;
  const double DIST_THRESHOLD = 0.05;

  CTicTac tictac;
  MyRansac myransac;

  myransac.setVerbosityLevel(mrpt::system::LVL_DEBUG);

  myransac.execute(
      data, &ransac3Dplane_fit, &ransac3Dplane_distance, &ransac3Dplane_degenerate, DIST_THRESHOLD,
      3,  // Minimum set of points
      best_inliers, best_model);

  cout << "Computation time: " << tictac.Tac() * 1000.0 << " ms\n";

  cout << "RANSAC finished: Best model: " << best_model.coefs[0] << " " << best_model.coefs[1]
       << " " << best_model.coefs[2] << " " << best_model.coefs[3] << endl;

  // Show GUI
  // --------------------------
  mrpt::gui::CDisplayWindow3D win("Set of points", 500, 500);
  opengl::Scene::Ptr scene = opengl::Scene::Create();

  scene->insert(opengl::CGridPlaneXY::Create(-20, 20, -20, 20, 0, 1));
  scene->insert(opengl::stock_objects::CornerXYZ());

  opengl::CPointCloud::Ptr points = opengl::CPointCloud::Create();
  points->setColor(0, 0, 1);
  points->setPointSize(3);
  points->enableColorFromZ();
  points->loadFromPointsMap(&data);

  scene->insert(points);

  opengl::CTexturedPlane::Ptr glPlane = opengl::CTexturedPlane::Create(-4, 4, -4, 4);

  glPlane->setColor_u8(mrpt::img::TColor(0xff, 0x00, 0x00, 0x80));  // RGBA

  TPose3D glPlanePose;
  best_model.getAsPose3D(glPlanePose);
  glPlane->setPose(glPlanePose);

  scene->insert(glPlane);

  win.get3DSceneAndLock() = scene;
  win.unlockAccess3DScene();
  win.forceRepaint();

  win.waitForKey();
}

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