GridMapPclConverter.cpp

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/*
 * GridMapPclConverter.cpp
 *
 *  Created on: Oct 19, 2016
 *      Author: Dominic Jud
 *   Institute: ETH Zurich, ANYbotics
 */

#include "grid_map_pcl/GridMapPclConverter.hpp"

namespace grid_map {

bool GridMapPclConverter::initializeFromPolygonMesh(const pcl::PolygonMesh& mesh, const double resolution, grid_map::GridMap& gridMap) {
  pcl::PointCloud<pcl::PointXYZ> cloud;
  pcl::fromPCLPointCloud2(mesh.cloud, cloud);
  pcl::PointXYZ minBound;
  pcl::PointXYZ maxBound;
  pcl::getMinMax3D(cloud, minBound, maxBound);

  grid_map::Length length = grid_map::Length(maxBound.x - minBound.x, maxBound.y - minBound.y);
  grid_map::Position position = grid_map::Position((maxBound.x + minBound.x) / 2.0, (maxBound.y + minBound.y) / 2.0);
  gridMap.setGeometry(length, resolution, position);

  return true;
}

bool GridMapPclConverter::addLayerFromPolygonMesh(const pcl::PolygonMesh& mesh, const std::string& layer, grid_map::GridMap& gridMap) {
  // Adding a layer to the grid map to put data into
  gridMap.add(layer);
  // Converting out of binary cloud data
  pcl::PointCloud<pcl::PointXYZ> cloud;
  pcl::fromPCLPointCloud2(mesh.cloud, cloud);
  // Direction and max height for projection ray
  const Eigen::Vector3f ray = -Eigen::Vector3f::UnitZ();
  pcl::PointXYZ minBound;
  pcl::PointXYZ maxBound;
  pcl::getMinMax3D(cloud, minBound, maxBound);

  // Iterating over the triangles in the mesh
  for (const pcl::Vertices& polygon : mesh.polygons) {
    // Testing this is a triangle
    assert(polygon.vertices.size() == 3);
    // Getting the vertices of the triangle (as a single matrix)
    Eigen::Matrix3f triangleVertexMatrix;
    triangleVertexMatrix.row(0) = cloud[polygon.vertices[0]].getVector3fMap();
    triangleVertexMatrix.row(1) = cloud[polygon.vertices[1]].getVector3fMap();
    triangleVertexMatrix.row(2) = cloud[polygon.vertices[2]].getVector3fMap();
    // Getting the bounds in the XY plane (down projection)
    float maxX = triangleVertexMatrix.col(0).maxCoeff();
    float minX = triangleVertexMatrix.col(0).minCoeff();
    float maxY = triangleVertexMatrix.col(1).maxCoeff();
    float minY = triangleVertexMatrix.col(1).minCoeff();
    // Iterating over the grid cells in the a submap below the triangle
    grid_map::Length length(maxX - minX, maxY - minY);
    grid_map::Position position((maxX + minX) / 2.0, (maxY + minY) / 2.0);
    bool isSuccess;
    SubmapGeometry submap(gridMap, position, length, isSuccess);
    if (isSuccess) {
      for (grid_map::SubmapIterator iterator(submap); !iterator.isPastEnd(); ++iterator) {
        // Cell position
        const Index index(*iterator);
        grid_map::Position vertexPositionXY;
        gridMap.getPosition(index, vertexPositionXY);
        // Ray origin
        Eigen::Vector3f point(vertexPositionXY.x(), vertexPositionXY.y(), maxBound.z + 1.0);
        // Vertical ray/triangle intersection
        Eigen::Vector3f intersectionPoint;
        if (rayTriangleIntersect(point, ray, triangleVertexMatrix, intersectionPoint)) {
          // If data already present in this cell, taking the max, else setting the data
          if (gridMap.isValid(index, layer)) {
            gridMap.at(layer, index) = std::max(gridMap.at(layer, index), intersectionPoint.z());
          } else {
            gridMap.at(layer, index) = intersectionPoint.z();
          }
        }
      }
    }
  }
  // Success
  return true;
}

bool GridMapPclConverter::rayTriangleIntersect(const Eigen::Vector3f& point, const Eigen::Vector3f& ray,
                                               const Eigen::Matrix3f& triangleVertexMatrix, Eigen::Vector3f& intersectionPoint) {
  // Algorithm here is adapted from:
  // http://softsurfer.com/Archive/algorithm_0105/algorithm_0105.htm#intersect_RayTriangle()
  //
  // Original copyright notice:
  // Copyright 2001, softSurfer (www.softsurfer.com)
  // This code may be freely used and modified for any purpose
  // providing that this copyright notice is included with it.

  const Eigen::Vector3f a = triangleVertexMatrix.row(0);
  const Eigen::Vector3f b = triangleVertexMatrix.row(1);
  const Eigen::Vector3f c = triangleVertexMatrix.row(2);
  const Eigen::Vector3f u = b - a;
  const Eigen::Vector3f v = c - a;
  const Eigen::Vector3f n = u.cross(v);
  const float n_dot_ray = n.dot(ray);

  if (std::fabs(n_dot_ray) < 1e-9) {
    return false;
  }

  const float r = n.dot(a - point) / n_dot_ray;

  if (r < 0) {
    return false;
  }

  // Note(alexmillane): The addition of this comparison delta (not in the
  // original algorithm) means that rays intersecting the edge of triangles are
  // treated at hits.
  constexpr float delta = 1e-5;

  const Eigen::Vector3f w = point + r * ray - a;
  const float denominator = u.dot(v) * u.dot(v) - u.dot(u) * v.dot(v);
  const float s_numerator = u.dot(v) * w.dot(v) - v.dot(v) * w.dot(u);
  const float s = s_numerator / denominator;
  if (s < (0 - delta) || s > (1 + delta)) {
    return false;
  }

  const float t_numerator = u.dot(v) * w.dot(u) - u.dot(u) * w.dot(v);
  const float t = t_numerator / denominator;
  if (t < (0 - delta) || s + t > (1 + delta)) {
    return false;
  }

  intersectionPoint = a + s * u + t * v;

  return true;
}

} /* namespace grid_map */