PlannerSimple2D.cpp

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2020, 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 "nav-precomp.h"  // Precompiled headers
//
#include <mrpt/math/TPose2D.h>
#include <mrpt/nav/planners/PlannerSimple2D.h>


using namespace mrpt;
using namespace mrpt::maps;
using namespace mrpt::math;
using namespace mrpt::poses;
using namespace mrpt::nav;
using namespace std;

/*---------------------------------------------------------------
                        computePath
  ---------------------------------------------------------------*/
void PlannerSimple2D::computePath(
    const COccupancyGridMap2D& theMap, const CPose2D& origin_,
    const CPose2D& target_, std::deque<math::TPoint2D>& path, bool& notFound,
    float maxSearchPathLength) const
{
    using cell_t = int32_t;

    constexpr cell_t CELL_ORIGIN = 0;
    constexpr cell_t CELL_EMPTY = 0x8000000;
    constexpr cell_t CELL_OBSTACLE = 0xfffffff;
    constexpr cell_t CELL_TARGET = 0xffffffe;

    path.clear();

    const TPoint2D origin = TPoint2D(origin_.asTPose());
    const TPoint2D target = TPoint2D(target_.asTPose());

    std::vector<cell_t> grid;
    int size_x, size_y, i, n, m;
    int x, y;
    bool searching;
    cell_t minNeigh = CELL_EMPTY, maxNeigh = CELL_EMPTY, v = 0, c;
    int passCellFound_x = -1, passCellFound_y = -1;
    std::vector<cell_t> pathcells_x, pathcells_y;

    // Check that origin and target falls inside the grid theMap
    // -----------------------------------------------------------
    if (!((origin.x > theMap.getXMin() && origin.x < theMap.getXMax() &&
           origin.y > theMap.getYMin() && origin.y < theMap.getYMax()) ||
          !(target.x > theMap.getXMin() && target.x < theMap.getXMax() &&
            target.y > theMap.getYMin() && target.y < theMap.getYMax())))
    {
        notFound = true;
        return;
    }

    // Check for the special case of origin and target in the same cell:
    // -----------------------------------------------------------------
    if (theMap.x2idx(origin.x) == theMap.x2idx(target.x) &&
        theMap.y2idx(origin.y) == theMap.y2idx(target.y))
    {
        path.emplace_back(target.x, target.y);
        notFound = false;
        return;
    }

    // Get the grid size:
    // -----------------------------------------------------------
    size_x = theMap.getSizeX();
    size_y = theMap.getSizeY();

    // Fill the grid content with free-space and obstacles:
    // -----------------------------------------------------------
    grid.resize(size_x * size_y);
    for (y = 0; y < size_y; y++)
    {
        int row = y * size_x;
        for (x = 0; x < size_x; x++)
        {
            grid[x + row] = (theMap.getCell(x, y) > occupancyThreshold)
                                ? CELL_EMPTY
                                : CELL_OBSTACLE;
        }
    }

    // Enlarge obstacles with the robot radius:
    // -----------------------------------------------------------
    int obsEnlargement = (int)(ceil(robotRadius / theMap.getResolution()));
    for (int nEnlargements = 0; nEnlargements < obsEnlargement; nEnlargements++)
    {
        // For all cells(x,y)=EMPTY:
        // -----------------------------
        for (y = 2; y < size_y - 2; y++)
        {
            int row = y * size_x;
            int row_1 = (y + 1) * size_x;
            int row__1 = (y - 1) * size_x;

            for (x = 2; x < size_x - 2; x++)
            {
                cell_t val = (CELL_OBSTACLE - nEnlargements);

                //  A cell near an obstacle found??
                // -----------------------------------------------------
                if (grid[x - 1 + row__1] >= val || grid[x + row__1] >= val ||
                    grid[x + 1 + row__1] >= val || grid[x - 1 + row] >= val ||
                    grid[x + 1 + row] >= val || grid[x - 1 + row_1] >= val ||
                    grid[x + row_1] >= val || grid[x + 1 + row_1] >= val)
                {
                    grid[x + row] = std::max(grid[x + row], val - 1);
                }
            }
        }
    }

    // Definitevely set new obstacles as obstacles
    for (auto& cell : grid)
        if (cell > CELL_EMPTY) cell = CELL_OBSTACLE;

    // Put the special cell codes for the origin and target:
    // -----------------------------------------------------------
    grid[theMap.x2idx(origin.x) + size_x * theMap.y2idx(origin.y)] =
        CELL_ORIGIN;
    grid[theMap.x2idx(target.x) + size_x * theMap.y2idx(target.y)] =
        CELL_TARGET;

    // The main path search loop:
    // -----------------------------------------------------------
    searching = true;  // Will become false on path found
    notFound = false;  // Will be true inside the loop if a path is not found

    int range_x_min =
        std::min(theMap.x2idx(origin.x) - 1, theMap.x2idx(target.x) - 1);
    int range_x_max =
        std::max(theMap.x2idx(origin.x) + 1, theMap.x2idx(target.x) + 1);
    int range_y_min =
        std::min(theMap.y2idx(origin.y) - 1, theMap.y2idx(target.y) - 1);
    int range_y_max =
        std::max(theMap.y2idx(origin.y) + 1, theMap.y2idx(target.y) + 1);

    do
    {
        notFound = true;
        bool wave1Found = false, wave2Found = false;
        int size_y_1 = size_y - 1;
        int size_x_1 = size_x - 1;

        range_x_min = std::max(1, range_x_min - 1);
        range_x_max = std::min(size_x_1, range_x_max + 1);
        range_y_min = std::max(1, range_y_min - 1);
        range_y_max = std::min(size_y_1, range_y_max + 1);

        // For all cells(x,y)=EMPTY:
        // -----------------------------
        for (y = range_y_min; y < range_y_max && passCellFound_x == -1; y++)
        {
            int row = y * size_x;
            int row_1 = (y + 1) * size_x;
            int row__1 = (y - 1) * size_x;
            // metric: 2 horz.vert, =3 diagonal <-- Since 3/2 ~= sqrt(2)
            cell_t metric;

            for (x = range_x_min; x < range_x_max; x++)
            {
                if (grid[x + row] != CELL_EMPTY) continue;

                //  Look in the neighboorhood:
                // -----------------------------
                minNeigh = maxNeigh = CELL_EMPTY;
                metric = 2;
                v = grid[x + row__1];
                if (v + 2 < minNeigh) minNeigh = v + 2;
                if (v - 2 > maxNeigh && v != CELL_OBSTACLE) maxNeigh = v - 2;
                v = grid[x - 1 + row];
                if (v + 2 < minNeigh) minNeigh = v + 2;
                if (v - 2 > maxNeigh && v != CELL_OBSTACLE) maxNeigh = v - 2;
                v = grid[x + 1 + row];
                if (v + 2 < minNeigh) minNeigh = v + 2;
                if (v - 2 > maxNeigh && v != CELL_OBSTACLE) maxNeigh = v - 2;
                v = grid[x + row_1];
                if (v + 2 < minNeigh) minNeigh = v + 2;
                if (v - 2 > maxNeigh && v != CELL_OBSTACLE) maxNeigh = v - 2;

                v = grid[x - 1 + row__1];
                if ((v + 3) < minNeigh)
                {
                    metric = 3;
                    minNeigh = (v + 3);
                }
                if ((v - 3) > maxNeigh && v != CELL_OBSTACLE)
                {
                    metric = 3;
                    maxNeigh = v - 3;
                }
                v = grid[x + 1 + row__1];
                if ((v + 3) < minNeigh)
                {
                    metric = 3;
                    minNeigh = (v + 3);
                }
                if ((v - 3) > maxNeigh && v != CELL_OBSTACLE)
                {
                    metric = 3;
                    maxNeigh = v - 3;
                }
                v = grid[x - 1 + row_1];
                if ((v + 3) < minNeigh)
                {
                    metric = 3;
                    minNeigh = (v + 3);
                }
                if ((v - 3) > maxNeigh && v != CELL_OBSTACLE)
                {
                    metric = 3;
                    maxNeigh = v - 3;
                }
                v = grid[x + 1 + row_1];
                if ((v + 3) < minNeigh)
                {
                    metric = 3;
                    minNeigh = (v + 3);
                }
                if ((v - 3) > maxNeigh && v != CELL_OBSTACLE)
                {
                    metric = 3;
                    maxNeigh = v - 3;
                }

                //  Convergence cell found? = The shortest path found
                // -----------------------------------------------------
                if (minNeigh < CELL_EMPTY && maxNeigh > CELL_EMPTY)
                {
                    // Stop the search:
                    passCellFound_x = x;
                    passCellFound_y = y;
                    searching = false;
                    break;
                }
                else if (minNeigh < CELL_EMPTY)
                {
                    wave1Found = true;

                    // Cell in the expansion-wave from origin
                    grid[x + row] = minNeigh + metric;
                    ASSERT_(minNeigh + metric < CELL_EMPTY);
                }
                else if (maxNeigh > CELL_EMPTY)
                {
                    wave2Found = true;

                    // Cell in the expansion-wave from the target
                    grid[x + row] = maxNeigh - metric;
                    ASSERT_(maxNeigh - metric > CELL_EMPTY);
                }
                else
                {  // Nothing to do: A free cell inside of all also free
                   // cells.
                }
            }  // end for x
        }  // end for y

        notFound = !wave1Found && !wave2Found;

        // Check max. path:
        const int estimPathLen = std::min(minNeigh + 1, CELL_TARGET - maxNeigh);

        if (maxSearchPathLength > 0 &&
            estimPathLen * theMap.getResolution() > maxSearchPathLength)
        {
            notFound = true;
            break;
        }

    } while (!notFound && searching);

    // Path not found:
    if (notFound) return;

    // Rebuild the optimal path from the two-waves convergence cell
    // ----------------------------------------------------------------

    // STEP 1: Trace-back to origin
    //-------------------------------------
    x = passCellFound_x;
    y = passCellFound_y;

    while ((v = grid[x + size_x * y]) != CELL_ORIGIN)
    {
        // Add cell to the path (in inverse order, now we go backward!!) Later
        // is will be reversed
        pathcells_x.push_back(x);
        pathcells_y.push_back(y);

        // Follow the "negative gradient" toward the origin:
        int8_t dx = 0, dy = 0;
        if ((c = grid[x - 1 + size_x * y]) < v)
        {
            v = c;
            dx = -1;
            dy = 0;
        }
        if ((c = grid[x + 1 + size_x * y]) < v)
        {
            v = c;
            dx = 1;
            dy = 0;
        }
        if ((c = grid[x + size_x * (y - 1)]) < v)
        {
            v = c;
            dx = 0;
            dy = -1;
        }
        if ((c = grid[x + size_x * (y + 1)]) < v)
        {
            v = c;
            dx = 0;
            dy = 1;
        }

        if ((c = grid[x - 1 + size_x * (y - 1)]) < v)
        {
            v = c;
            dx = -1;
            dy = -1;
        }
        if ((c = grid[x + 1 + size_x * (y - 1)]) < v)
        {
            v = c;
            dx = 1;
            dy = -1;
        }
        if ((c = grid[x - 1 + size_x * (y + 1)]) < v)
        {
            v = c;
            dx = -1;
            dy = 1;
        }
        if ((c = grid[x + 1 + size_x * (y + 1)]) < v)
        {
            v = c;
            dx = 1;
            dy = 1;
        }

        ASSERT_(dx != 0 || dy != 0);
        x += dx;
        y += dy;
    }

    // STEP 2: Reverse the path, since we want it from the origin
    //   toward the convergence cell
    //--------------------------------------------------------------
    n = pathcells_x.size();
    m = n / 2;
    for (i = 0; i < m; i++)
    {
        v = pathcells_x[i];
        pathcells_x[i] = pathcells_x[n - 1 - i];
        pathcells_x[n - 1 - i] = v;

        v = pathcells_y[i];
        pathcells_y[i] = pathcells_y[n - 1 - i];
        pathcells_y[n - 1 - i] = v;
    }

    // STEP 3: Trace-foward toward the target
    //-------------------------------------
    x = passCellFound_x;
    y = passCellFound_y;

    while ((v = grid[x + size_x * y]) != CELL_TARGET)
    {
        // Add cell to the path
        pathcells_x.push_back(x);
        pathcells_y.push_back(y);

        // Follow the "positive gradient" toward the target:
        static signed char dx = 0, dy = 0;
        c = grid[x - 1 + size_x * y];
        if (c > v && c != CELL_OBSTACLE)
        {
            v = c;
            dx = -1;
            dy = 0;
        }
        c = grid[x + 1 + size_x * y];
        if (c > v && c != CELL_OBSTACLE)
        {
            v = c;
            dx = 1;
            dy = 0;
        }
        c = grid[x + size_x * (y - 1)];
        if (c > v && c != CELL_OBSTACLE)
        {
            v = c;
            dx = 0;
            dy = -1;
        }
        c = grid[x + size_x * (y + 1)];
        if (c > v && c != CELL_OBSTACLE)
        {
            v = c;
            dx = 0;
            dy = 1;
        }

        c = grid[x - 1 + size_x * (y - 1)];
        if (c > v && c != CELL_OBSTACLE)
        {
            v = c;
            dx = -1;
            dy = -1;
        }
        c = grid[x + 1 + size_x * (y - 1)];
        if (c > v && c != CELL_OBSTACLE)
        {
            v = c;
            dx = 1;
            dy = -1;
        }
        c = grid[x - 1 + size_x * (y + 1)];
        if (c > v && c != CELL_OBSTACLE)
        {
            v = c;
            dx = -1;
            dy = 1;
        }
        c = grid[x + 1 + size_x * (y + 1)];
        if (c > v && c != CELL_OBSTACLE)
        {
            v = c;
            dx = 1;
            dy = 1;
        }

        ASSERT_(dx != 0 || dy != 0);
        x += dx;
        y += dy;
    }

    // STEP 4: Translate the path-of-cells to a path-of-2d-points with
    // subsampling
    //-------------------------------------------------------------------------------
    path.clear();
    n = pathcells_x.size();
    double last_xx = origin.x;
    double last_yy = origin.y;
    auto last_cx = theMap.x2idx(origin.x);
    auto last_cy = theMap.y2idx(origin.y);

    const auto minDistSqrCells = mrpt::round(
        mrpt::square(minStepInReturnedPath / theMap.getResolution()));
    double accumDist = 0;
    for (i = 0; i < n; i++)
    {
        // Enough distance??
        const auto distSqrCells =
            square(pathcells_x[i] - last_cx) + square(pathcells_y[i] - last_cy);

        if (distSqrCells > minDistSqrCells)
        {
            // Get cell coordinates:
            auto xx = theMap.idx2x(pathcells_x[i]);
            auto yy = theMap.idx2y(pathcells_y[i]);

            // Add to the path:
            path.emplace_back(xx, yy);

            accumDist += std::sqrt(square(xx - last_xx) + square(yy - last_yy));

            // For the next iteration:
            last_cx = pathcells_x[i];
            last_cy = pathcells_y[i];
            last_xx = xx;
            last_yy = yy;
        }

        if (maxSearchPathLength > 0 && accumDist > maxSearchPathLength)
        {
            notFound = true;
            path.clear();
            return;
        }
    }

    // Add the target point:
    path.emplace_back(target.x, target.y);

    // That's all!! :-)
}