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zr-v4/libraries/AC_Avoidance/AP_OADijkstra.cpp

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/*
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "AP_OADijkstra.h"
#include <AC_Fence/AC_Fence.h>
#include <AP_AHRS/AP_AHRS.h>
#include <AP_Logger/AP_Logger.h>
#define OA_DIJKSTRA_EXPANDING_ARRAY_ELEMENTS_PER_CHUNK 32 // expanding arrays for fence points and paths to destination will grow in increments of 20 elements
#define OA_DIJKSTRA_POLYGON_SHORTPATH_NOTSET_IDX 255 // index use to indicate we do not have a tentative short path for a node
#define OA_DIJKSTRA_ERROR_REPORTING_INTERVAL_MS 5000 // failure messages sent to GCS every 5 seconds
/// Constructor
AP_OADijkstra::AP_OADijkstra() :
_inclusion_polygon_pts(OA_DIJKSTRA_EXPANDING_ARRAY_ELEMENTS_PER_CHUNK),
_exclusion_polygon_pts(OA_DIJKSTRA_EXPANDING_ARRAY_ELEMENTS_PER_CHUNK),
_exclusion_circle_pts(OA_DIJKSTRA_EXPANDING_ARRAY_ELEMENTS_PER_CHUNK),
_short_path_data(OA_DIJKSTRA_EXPANDING_ARRAY_ELEMENTS_PER_CHUNK),
_path(OA_DIJKSTRA_EXPANDING_ARRAY_ELEMENTS_PER_CHUNK)
{
}
// calculate a destination to avoid fences
// returns DIJKSTRA_STATE_SUCCESS and populates origin_new and destination_new if avoidance is required
AP_OADijkstra::AP_OADijkstra_State AP_OADijkstra::update(const Location &current_loc, const Location &destination, Location& origin_new, Location& destination_new)
{
// require ekf origin to have been set
struct Location ekf_origin {};
{
WITH_SEMAPHORE(AP::ahrs().get_semaphore());
if (!AP::ahrs().get_origin(ekf_origin)) {
AP::logger().Write_OADijkstra(DIJKSTRA_STATE_NOT_REQUIRED, 0, 0, 0, destination, destination);
return DIJKSTRA_STATE_NOT_REQUIRED;
}
}
WITH_SEMAPHORE(AP::fence()->polyfence().get_loaded_fence_semaphore());
// avoidance is not required if no fences
if (!some_fences_enabled()) {
AP::logger().Write_OADijkstra(DIJKSTRA_STATE_NOT_REQUIRED, 0, 0, 0, destination, destination);
return DIJKSTRA_STATE_NOT_REQUIRED;
}
// no avoidance required if destination is same as current location
if (current_loc.same_latlon_as(destination)) {
AP::logger().Write_OADijkstra(DIJKSTRA_STATE_NOT_REQUIRED, 0, 0, 0, destination, destination);
return DIJKSTRA_STATE_NOT_REQUIRED;
}
// check for inclusion polygon updates
if (check_inclusion_polygon_updated()) {
_inclusion_polygon_with_margin_ok = false;
_polyfence_visgraph_ok = false;
_shortest_path_ok = false;
}
// check for exclusion polygon updates
if (check_exclusion_polygon_updated()) {
_exclusion_polygon_with_margin_ok = false;
_polyfence_visgraph_ok = false;
_shortest_path_ok = false;
}
// check for exclusion circle updates
if (check_exclusion_circle_updated()) {
_exclusion_circle_with_margin_ok = false;
_polyfence_visgraph_ok = false;
_shortest_path_ok = false;
}
// create inner polygon fence
AP_OADijkstra_Error error_id;
if (!_inclusion_polygon_with_margin_ok) {
_inclusion_polygon_with_margin_ok = create_inclusion_polygon_with_margin(_polyfence_margin * 100.0f, error_id);
if (!_inclusion_polygon_with_margin_ok) {
report_error(error_id);
AP::logger().Write_OADijkstra(DIJKSTRA_STATE_ERROR, (uint8_t)error_id, 0, 0, destination, destination);
return DIJKSTRA_STATE_ERROR;
}
}
// create exclusion polygon outer fence
if (!_exclusion_polygon_with_margin_ok) {
_exclusion_polygon_with_margin_ok = create_exclusion_polygon_with_margin(_polyfence_margin * 100.0f, error_id);
if (!_exclusion_polygon_with_margin_ok) {
report_error(error_id);
AP::logger().Write_OADijkstra(DIJKSTRA_STATE_ERROR, (uint8_t)error_id, 0, 0, destination, destination);
return DIJKSTRA_STATE_ERROR;
}
}
// create exclusion circle points
if (!_exclusion_circle_with_margin_ok) {
_exclusion_circle_with_margin_ok = create_exclusion_circle_with_margin(_polyfence_margin * 100.0f, error_id);
if (!_exclusion_circle_with_margin_ok) {
report_error(error_id);
AP::logger().Write_OADijkstra(DIJKSTRA_STATE_ERROR, (uint8_t)error_id, 0, 0, destination, destination);
return DIJKSTRA_STATE_ERROR;
}
}
// create visgraph for all fence (with margin) points
if (!_polyfence_visgraph_ok) {
_polyfence_visgraph_ok = create_fence_visgraph(error_id);
if (!_polyfence_visgraph_ok) {
_shortest_path_ok = false;
report_error(error_id);
AP::logger().Write_OADijkstra(DIJKSTRA_STATE_ERROR, (uint8_t)error_id, 0, 0, destination, destination);
return DIJKSTRA_STATE_ERROR;
}
}
// rebuild path if destination has changed
if (!destination.same_latlon_as(_destination_prev)) {
_destination_prev = destination;
_shortest_path_ok = false;
}
// calculate shortest path from current_loc to destination
if (!_shortest_path_ok) {
_shortest_path_ok = calc_shortest_path(current_loc, destination, error_id);
if (!_shortest_path_ok) {
report_error(error_id);
AP::logger().Write_OADijkstra(DIJKSTRA_STATE_ERROR, (uint8_t)error_id, 0, 0, destination, destination);
return DIJKSTRA_STATE_ERROR;
}
// start from 2nd point on path (first is the original origin)
_path_idx_returned = 1;
}
// path has been created, return latest point
Vector2f dest_pos;
if (get_shortest_path_point(_path_idx_returned, dest_pos)) {
// for the first point return origin as current_loc
Vector2f origin_pos;
if ((_path_idx_returned > 0) && get_shortest_path_point(_path_idx_returned-1, origin_pos)) {
// convert offset from ekf origin to Location
Location temp_loc(Vector3f(origin_pos.x, origin_pos.y, 0.0f));
origin_new = temp_loc;
} else {
// for first point use current loc as origin
origin_new = current_loc;
}
// convert offset from ekf origin to Location
Location temp_loc(Vector3f(dest_pos.x, dest_pos.y, 0.0f));
destination_new = destination;
destination_new.lat = temp_loc.lat;
destination_new.lng = temp_loc.lng;
// check if we should advance to next point for next iteration
const bool near_oa_wp = current_loc.get_distance(destination_new) <= 2.0f;
const bool past_oa_wp = current_loc.past_interval_finish_line(origin_new, destination_new);
if (near_oa_wp || past_oa_wp) {
_path_idx_returned++;
}
// log success
AP::logger().Write_OADijkstra(DIJKSTRA_STATE_SUCCESS, 0, _path_idx_returned, _path_numpoints, destination, destination_new);
return DIJKSTRA_STATE_SUCCESS;
}
// we have reached the destination so avoidance is no longer required
AP::logger().Write_OADijkstra(DIJKSTRA_STATE_NOT_REQUIRED, 0, 0, 0, destination, destination);
return DIJKSTRA_STATE_NOT_REQUIRED;
}
// returns true if at least one inclusion or exclusion zone is enabled
bool AP_OADijkstra::some_fences_enabled() const
{
const AC_Fence *fence = AC_Fence::get_singleton();
if (fence == nullptr) {
return false;
}
if ((fence->polyfence().get_inclusion_polygon_count() == 0) &&
(fence->polyfence().get_exclusion_polygon_count() == 0) &&
(fence->polyfence().get_exclusion_circle_count() == 0)) {
return false;
}
return ((fence->get_enabled_fences() & AC_FENCE_TYPE_POLYGON) > 0);
}
// return error message for a given error id
const char* AP_OADijkstra::get_error_msg(AP_OADijkstra_Error error_id) const
{
switch (error_id) {
case AP_OADijkstra_Error::DIJKSTRA_ERROR_NONE:
return "no error";
break;
case AP_OADijkstra_Error::DIJKSTRA_ERROR_OUT_OF_MEMORY:
return "out of memory";
break;
case AP_OADijkstra_Error::DIJKSTRA_ERROR_OVERLAPPING_POLYGON_POINTS:
return "overlapping polygon points";
break;
case AP_OADijkstra_Error::DIJKSTRA_ERROR_FAILED_TO_BUILD_INNER_POLYGON:
return "failed to build inner polygon";
break;
case AP_OADijkstra_Error::DIJKSTRA_ERROR_OVERLAPPING_POLYGON_LINES:
return "overlapping polygon lines";
break;
case AP_OADijkstra_Error::DIJKSTRA_ERROR_FENCE_DISABLED:
return "fence disabled";
break;
case AP_OADijkstra_Error::DIJKSTRA_ERROR_TOO_MANY_FENCE_POINTS:
return "too many fence points";
break;
case AP_OADijkstra_Error::DIJKSTRA_ERROR_NO_POSITION_ESTIMATE:
return "no position estimate";
break;
case AP_OADijkstra_Error::DIJKSTRA_ERROR_COULD_NOT_FIND_PATH:
return "could not find path";
break;
}
// we should never reach here but just in case
return "unknown error";
}
void AP_OADijkstra::report_error(AP_OADijkstra_Error error_id)
{
// report errors to GCS every 5 seconds
uint32_t now_ms = AP_HAL::millis();
if ((error_id != AP_OADijkstra_Error::DIJKSTRA_ERROR_NONE) &&
((error_id != _error_last_id) || ((now_ms - _error_last_report_ms) > OA_DIJKSTRA_ERROR_REPORTING_INTERVAL_MS))) {
const char* error_msg = get_error_msg(error_id);
gcs().send_text(MAV_SEVERITY_CRITICAL, "Dijkstra: %s", error_msg);
_error_last_id = error_id;
_error_last_report_ms = now_ms;
}
}
// check if polygon fence has been updated since we created the inner fence. returns true if changed
bool AP_OADijkstra::check_inclusion_polygon_updated() const
{
// exit immediately if polygon fence is not enabled
const AC_Fence *fence = AC_Fence::get_singleton();
if (fence == nullptr) {
return false;
}
return (_inclusion_polygon_update_ms != fence->polyfence().get_inclusion_polygon_update_ms());
}
// create polygons inside the existing inclusion polygons
// returns true on success. returns false on failure and err_id is updated
bool AP_OADijkstra::create_inclusion_polygon_with_margin(float margin_cm, AP_OADijkstra_Error &err_id)
{
const AC_Fence *fence = AC_Fence::get_singleton();
if (fence == nullptr) {
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_FENCE_DISABLED;
return false;
}
// clear all points
_inclusion_polygon_numpoints = 0;
// return immediately if no polygons
const uint8_t num_inclusion_polygons = fence->polyfence().get_inclusion_polygon_count();
// iterate through polygons and create inner points
for (uint8_t i = 0; i < num_inclusion_polygons; i++) {
uint16_t num_points;
const Vector2f* boundary = fence->polyfence().get_inclusion_polygon(i, num_points);
if (num_points < 3) {
// ignore exclusion polygons with less than 3 points
continue;
}
// expand array if required
if (!_inclusion_polygon_pts.expand_to_hold(_inclusion_polygon_numpoints + num_points)) {
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_OUT_OF_MEMORY;
return false;
}
// for each point in inclusion polygon
// Note: boundary is "unclosed" meaning the last point is *not* the same as the first
for (uint16_t j = 0; j < num_points; j++) {
// find points before and after current point (relative to current point)
const uint16_t before_idx = (j == 0) ? num_points-1 : j-1;
const uint16_t after_idx = (j == num_points-1) ? 0 : j+1;
Vector2f before_pt = boundary[before_idx] - boundary[j];
Vector2f after_pt = boundary[after_idx] - boundary[j];
// if points are overlapping fail
if (before_pt.is_zero() || after_pt.is_zero() || (before_pt == after_pt)) {
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_OVERLAPPING_POLYGON_POINTS;
return false;
}
// scale points to be unit vectors
before_pt.normalize();
after_pt.normalize();
// calculate intermediate point and scale to margin
Vector2f intermediate_pt = (after_pt + before_pt) * 0.5f;
float intermediate_len = intermediate_pt.length();
intermediate_pt *= (margin_cm / intermediate_len);
// find final point which is outside the inside polygon
uint16_t next_index = _inclusion_polygon_numpoints + j;
_inclusion_polygon_pts[next_index] = boundary[j] + intermediate_pt;
if (Polygon_outside(_inclusion_polygon_pts[next_index], boundary, num_points)) {
_inclusion_polygon_pts[next_index] = boundary[j] - intermediate_pt;
if (Polygon_outside(_inclusion_polygon_pts[next_index], boundary, num_points)) {
// could not find a point on either side that was outside the exclusion polygon so fail
// this may happen if the exclusion polygon has overlapping lines
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_OVERLAPPING_POLYGON_LINES;
return false;
}
}
}
// update total number of points
_inclusion_polygon_numpoints += num_points;
}
// record fence update time so we don't process these inclusion polygons again
_inclusion_polygon_update_ms = fence->polyfence().get_inclusion_polygon_update_ms();
return true;
}
// check if exclusion polygons have been updated since create_exclusion_polygon_with_margin was run
// returns true if changed
bool AP_OADijkstra::check_exclusion_polygon_updated() const
{
const AC_Fence *fence = AC_Fence::get_singleton();
if (fence == nullptr) {
return false;
}
return (_exclusion_polygon_update_ms != fence->polyfence().get_exclusion_polygon_update_ms());
}
// create polygons around existing exclusion polygons
// returns true on success. returns false on failure and err_id is updated
bool AP_OADijkstra::create_exclusion_polygon_with_margin(float margin_cm, AP_OADijkstra_Error &err_id)
{
const AC_Fence *fence = AC_Fence::get_singleton();
if (fence == nullptr) {
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_FENCE_DISABLED;
return false;
}
// clear all points
_exclusion_polygon_numpoints = 0;
// return immediately if no exclusion polygons
const uint8_t num_exclusion_polygons = fence->polyfence().get_exclusion_polygon_count();
// iterate through exclusion polygons and create outer points
for (uint8_t i = 0; i < num_exclusion_polygons; i++) {
uint16_t num_points;
const Vector2f* boundary = fence->polyfence().get_exclusion_polygon(i, num_points);
if (num_points < 3) {
// ignore exclusion polygons with less than 3 points
continue;
}
// expand array if required
if (!_exclusion_polygon_pts.expand_to_hold(_exclusion_polygon_numpoints + num_points)) {
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_OUT_OF_MEMORY;
return false;
}
// for each point in exclusion polygon
// Note: boundary is "unclosed" meaning the last point is *not* the same as the first
for (uint16_t j = 0; j < num_points; j++) {
// find points before and after current point (relative to current point)
const uint16_t before_idx = (j == 0) ? num_points-1 : j-1;
const uint16_t after_idx = (j == num_points-1) ? 0 : j+1;
Vector2f before_pt = boundary[before_idx] - boundary[j];
Vector2f after_pt = boundary[after_idx] - boundary[j];
// if points are overlapping fail
if (before_pt.is_zero() || after_pt.is_zero() || (before_pt == after_pt)) {
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_OVERLAPPING_POLYGON_POINTS;
return false;
}
// scale points to be unit vectors
before_pt.normalize();
after_pt.normalize();
// calculate intermediate point and scale to margin
Vector2f intermediate_pt = (after_pt + before_pt) * 0.5f;
float intermediate_len = intermediate_pt.length();
intermediate_pt *= (margin_cm / intermediate_len);
// find final point which is outside the original polygon
uint16_t next_index = _exclusion_polygon_numpoints + j;
_exclusion_polygon_pts[next_index] = boundary[j] + intermediate_pt;
if (!Polygon_outside(_exclusion_polygon_pts[next_index], boundary, num_points)) {
_exclusion_polygon_pts[next_index] = boundary[j] - intermediate_pt;
if (!Polygon_outside(_exclusion_polygon_pts[next_index], boundary, num_points)) {
// could not find a point on either side that was outside the exclusion polygon so fail
// this may happen if the exclusion polygon has overlapping lines
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_OVERLAPPING_POLYGON_LINES;
return false;
}
}
}
// update total number of points
_exclusion_polygon_numpoints += num_points;
}
// record fence update time so we don't process these exclusion polygons again
_exclusion_polygon_update_ms = fence->polyfence().get_exclusion_polygon_update_ms();
return true;
}
// check if exclusion circles have been updated since create_exclusion_circle_with_margin was run
// returns true if changed
bool AP_OADijkstra::check_exclusion_circle_updated() const
{
// exit immediately if fence is not enabled
const AC_Fence *fence = AC_Fence::get_singleton();
if (fence == nullptr) {
return false;
}
return (_exclusion_circle_update_ms != fence->polyfence().get_exclusion_circle_update_ms());
}
// create polygons around existing exclusion circles
// returns true on success. returns false on failure and err_id is updated
bool AP_OADijkstra::create_exclusion_circle_with_margin(float margin_cm, AP_OADijkstra_Error &err_id)
{
// exit immediately if fence is not enabled
const AC_Fence *fence = AC_Fence::get_singleton();
if (fence == nullptr) {
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_FENCE_DISABLED;
return false;
}
// clear all points
_exclusion_circle_numpoints = 0;
// unit length offsets for polygon points around circles
const Vector2f unit_offsets[] = {
{cosf(radians(30)), cosf(radians(30-90))}, // north-east
{cosf(radians(90)), cosf(radians(90-90))}, // east
{cosf(radians(150)), cosf(radians(150-90))},// south-east
{cosf(radians(210)), cosf(radians(210-90))},// south-west
{cosf(radians(270)), cosf(radians(270-90))},// west
{cosf(radians(330)), cosf(radians(330-90))},// north-west
};
const uint8_t num_points_per_circle = ARRAY_SIZE(unit_offsets);
// expand polygon point array if required
const uint8_t num_exclusion_circles = fence->polyfence().get_exclusion_circle_count();
if (!_exclusion_circle_pts.expand_to_hold(num_exclusion_circles * num_points_per_circle)) {
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_OUT_OF_MEMORY;
return false;
}
// iterate through exclusion circles and create outer polygon points
for (uint8_t i = 0; i < num_exclusion_circles; i++) {
Vector2f circle_pos_cm;
float radius;
if (fence->polyfence().get_exclusion_circle(i, circle_pos_cm, radius)) {
// scaler to ensure lines between points do not intersect circle
const float scaler = (1.0f / cosf(radians(180.0f / (float)num_points_per_circle))) * ((radius * 100.0f) + margin_cm);
// add points to array
for (uint8_t j = 0; j < num_points_per_circle; j++) {
_exclusion_circle_pts[_exclusion_circle_numpoints] = circle_pos_cm + (unit_offsets[j] * scaler);
_exclusion_circle_numpoints++;
}
}
}
// record fence update time so we don't process these exclusion circles again
_exclusion_circle_update_ms = fence->polyfence().get_exclusion_circle_update_ms();
return true;
}
// returns total number of points across all fence types
uint16_t AP_OADijkstra::total_numpoints() const
{
return _inclusion_polygon_numpoints + _exclusion_polygon_numpoints + _exclusion_circle_numpoints;
}
// get a single point across the total list of points from all fence types
bool AP_OADijkstra::get_point(uint16_t index, Vector2f &point) const
{
// sanity check index
if (index >= total_numpoints()) {
return false;
}
// return an inclusion polygon point
if (index < _inclusion_polygon_numpoints) {
point = _inclusion_polygon_pts[index];
return true;
}
index -= _inclusion_polygon_numpoints;
// return an exclusion polygon point
if (index < _exclusion_polygon_numpoints) {
point = _exclusion_polygon_pts[index];
return true;
}
index -= _exclusion_polygon_numpoints;
// return an exclusion circle point
if (index < _exclusion_circle_numpoints) {
point = _exclusion_circle_pts[index];
return true;
}
// we should never get here but just in case
return false;
}
// returns true if line segment intersects polygon or circular fence
bool AP_OADijkstra::intersects_fence(const Vector2f &seg_start, const Vector2f &seg_end) const
{
// return immediately if fence is not enabled
const AC_Fence *fence = AC_Fence::get_singleton();
if (fence == nullptr) {
return false;
}
// determine if segment crosses any of the inclusion polygons
uint16_t num_points = 0;
for (uint8_t i = 0; i < fence->polyfence().get_inclusion_polygon_count(); i++) {
const Vector2f* boundary = fence->polyfence().get_inclusion_polygon(i, num_points);
if ((boundary != nullptr) && (num_points >= 3)) {
Vector2f intersection;
if (Polygon_intersects(boundary, num_points, seg_start, seg_end, intersection)) {
return true;
}
}
}
// determine if segment crosses any of the exclusion polygons
for (uint8_t i = 0; i < fence->polyfence().get_exclusion_polygon_count(); i++) {
const Vector2f* boundary = fence->polyfence().get_exclusion_polygon(i, num_points);
if ((boundary != nullptr) && (num_points >= 3)) {
Vector2f intersection;
if (Polygon_intersects(boundary, num_points, seg_start, seg_end, intersection)) {
return true;
}
}
}
// determine if segment crosses any of the inclusion circles
for (uint8_t i = 0; i < fence->polyfence().get_inclusion_circle_count(); i++) {
Vector2f center_pos_cm;
float radius;
if (fence->polyfence().get_inclusion_circle(i, center_pos_cm, radius)) {
// intersects circle if either start or end is further from the center than the radius
const float radius_cm_sq = sq(radius * 100.0f) ;
if ((seg_start - center_pos_cm).length_squared() > radius_cm_sq) {
return true;
}
if ((seg_end - center_pos_cm).length_squared() > radius_cm_sq) {
return true;
}
}
}
// determine if segment crosses any of the exclusion circles
for (uint8_t i = 0; i < fence->polyfence().get_exclusion_circle_count(); i++) {
Vector2f center_pos_cm;
float radius;
if (fence->polyfence().get_exclusion_circle(i, center_pos_cm, radius)) {
// calculate distance between circle's center and segment
const float dist_cm = Vector2f::closest_distance_between_line_and_point(seg_start, seg_end, center_pos_cm);
// intersects if distance is less than radius
if (dist_cm <= (radius * 100.0f)) {
return true;
}
}
}
// if we got this far then no intersection
return false;
}
// create visibility graph for all fence (with margin) points
// returns true on success. returns false on failure and err_id is updated
// requires these functions to have been run create_inclusion_polygon_with_margin, create_exclusion_polygon_with_margin, create_exclusion_circle_with_margin
bool AP_OADijkstra::create_fence_visgraph(AP_OADijkstra_Error &err_id)
{
// exit immediately if fence is not enabled
const AC_Fence *fence = AC_Fence::get_singleton();
if (fence == nullptr) {
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_FENCE_DISABLED;
return false;
}
// fail if more fence points than algorithm can handle
if (total_numpoints() >= OA_DIJKSTRA_POLYGON_SHORTPATH_NOTSET_IDX) {
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_TOO_MANY_FENCE_POINTS;
return false;
}
// clear fence points visibility graph
_fence_visgraph.clear();
// calculate distance from each point to all other points
for (uint8_t i = 0; i < total_numpoints() - 1; i++) {
Vector2f start_seg;
if (get_point(i, start_seg)) {
for (uint8_t j = i + 1; j < total_numpoints(); j++) {
Vector2f end_seg;
if (get_point(j, end_seg)) {
// if line segment does not intersect with any inclusion or exclusion zones add to visgraph
if (!intersects_fence(start_seg, end_seg)) {
if (!_fence_visgraph.add_item({AP_OAVisGraph::OATYPE_INTERMEDIATE_POINT, i},
{AP_OAVisGraph::OATYPE_INTERMEDIATE_POINT, j},
(start_seg - end_seg).length())) {
// failure to add a point can only be caused by out-of-memory
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_OUT_OF_MEMORY;
return false;
}
}
}
}
}
}
return true;
}
// updates visibility graph for a given position which is an offset (in cm) from the ekf origin
// to add an additional position (i.e. the destination) set add_extra_position = true and provide the position in the extra_position argument
// requires create_inclusion_polygon_with_margin to have been run
// returns true on success
bool AP_OADijkstra::update_visgraph(AP_OAVisGraph& visgraph, const AP_OAVisGraph::OAItemID& oaid, const Vector2f &position, bool add_extra_position, Vector2f extra_position)
{
// exit immediately if no fence (with margin) points
if (total_numpoints() == 0) {
return false;
}
// clear visibility graph
visgraph.clear();
// calculate distance from position to all inclusion/exclusion fence points
for (uint8_t i = 0; i < total_numpoints(); i++) {
Vector2f seg_end;
if (get_point(i, seg_end)) {
if (!intersects_fence(position, seg_end)) {
// line segment does not intersect with fences so add to visgraph
if (!visgraph.add_item(oaid, {AP_OAVisGraph::OATYPE_INTERMEDIATE_POINT, i}, (position - seg_end).length())) {
return false;
}
}
}
}
// add extra point to visibility graph if it doesn't intersect with polygon fence or exclusion polygons
if (add_extra_position) {
if (!intersects_fence(position, extra_position)) {
if (!visgraph.add_item(oaid, {AP_OAVisGraph::OATYPE_DESTINATION, 0}, (position - extra_position).length())) {
return false;
}
}
}
return true;
}
// update total distance for all nodes visible from current node
// curr_node_idx is an index into the _short_path_data array
void AP_OADijkstra::update_visible_node_distances(node_index curr_node_idx)
{
// sanity check
if (curr_node_idx >= _short_path_data_numpoints) {
return;
}
// get current node for convenience
const ShortPathNode &curr_node = _short_path_data[curr_node_idx];
// for each visibility graph
const AP_OAVisGraph* visgraphs[] = {&_fence_visgraph, &_destination_visgraph};
for (uint8_t v=0; v<ARRAY_SIZE(visgraphs); v++) {
// skip if empty
const AP_OAVisGraph &curr_visgraph = *visgraphs[v];
if (curr_visgraph.num_items() == 0) {
continue;
}
// search visibility graph for items visible from current_node
for (uint16_t i = 0; i < curr_visgraph.num_items(); i++) {
const AP_OAVisGraph::VisGraphItem &item = curr_visgraph[i];
// match if current node's id matches either of the id's in the graph (i.e. either end of the vector)
if ((curr_node.id == item.id1) || (curr_node.id == item.id2)) {
AP_OAVisGraph::OAItemID matching_id = (curr_node.id == item.id1) ? item.id2 : item.id1;
// find item's id in node array
node_index item_node_idx;
if (find_node_from_id(matching_id, item_node_idx)) {
// if current node's distance + distance to item is less than item's current distance, update item's distance
const float dist_to_item_via_current_node = _short_path_data[curr_node_idx].distance_cm + item.distance_cm;
if (dist_to_item_via_current_node < _short_path_data[item_node_idx].distance_cm) {
// update item's distance and set "distance_from_idx" to current node's index
_short_path_data[item_node_idx].distance_cm = dist_to_item_via_current_node;
_short_path_data[item_node_idx].distance_from_idx = curr_node_idx;
}
}
}
}
}
}
// find a node's index into _short_path_data array from it's id (i.e. id type and id number)
// returns true if successful and node_idx is updated
bool AP_OADijkstra::find_node_from_id(const AP_OAVisGraph::OAItemID &id, node_index &node_idx) const
{
switch (id.id_type) {
case AP_OAVisGraph::OATYPE_SOURCE:
// source node is always the first node
if (_short_path_data_numpoints > 0) {
node_idx = 0;
return true;
}
break;
case AP_OAVisGraph::OATYPE_DESTINATION:
// destination is always the 2nd node
if (_short_path_data_numpoints > 1) {
node_idx = 1;
return true;
}
break;
case AP_OAVisGraph::OATYPE_INTERMEDIATE_POINT:
// intermediate nodes start from 3rd node
if (_short_path_data_numpoints > id.id_num + 2) {
node_idx = id.id_num + 2;
return true;
}
break;
}
// could not find node
return false;
}
// find index of node with lowest tentative distance (ignore visited nodes)
// returns true if successful and node_idx argument is updated
bool AP_OADijkstra::find_closest_node_idx(node_index &node_idx) const
{
node_index lowest_idx = 0;
float lowest_dist = FLT_MAX;
// scan through all nodes looking for closest
for (node_index i=0; i<_short_path_data_numpoints; i++) {
const ShortPathNode &node = _short_path_data[i];
if (!node.visited && (node.distance_cm < lowest_dist)) {
lowest_idx = i;
lowest_dist = node.distance_cm;
}
}
if (lowest_dist < FLT_MAX) {
node_idx = lowest_idx;
return true;
}
return false;
}
// calculate shortest path from origin to destination
// returns true on success. returns false on failure and err_id is updated
// requires these functions to have been run: create_inclusion_polygon_with_margin, create_exclusion_polygon_with_margin, create_exclusion_circle_with_margin, create_polygon_fence_visgraph
// resulting path is stored in _shortest_path array as vector offsets from EKF origin
bool AP_OADijkstra::calc_shortest_path(const Location &origin, const Location &destination, AP_OADijkstra_Error &err_id)
{
// convert origin and destination to offsets from EKF origin
Vector2f origin_NE, destination_NE;
if (!origin.get_vector_xy_from_origin_NE(origin_NE) || !destination.get_vector_xy_from_origin_NE(destination_NE)) {
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_NO_POSITION_ESTIMATE;
return false;
}
// create visgraphs of origin and destination to fence points
if (!update_visgraph(_source_visgraph, {AP_OAVisGraph::OATYPE_SOURCE, 0}, origin_NE, true, destination_NE)) {
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_OUT_OF_MEMORY;
return false;
}
if (!update_visgraph(_destination_visgraph, {AP_OAVisGraph::OATYPE_DESTINATION, 0}, destination_NE)) {
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_OUT_OF_MEMORY;
return false;
}
// expand _short_path_data if necessary
if (!_short_path_data.expand_to_hold(2 + total_numpoints())) {
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_OUT_OF_MEMORY;
return false;
}
// add origin and destination (node_type, id, visited, distance_from_idx, distance_cm) to short_path_data array
_short_path_data[0] = {{AP_OAVisGraph::OATYPE_SOURCE, 0}, false, 0, 0};
_short_path_data[1] = {{AP_OAVisGraph::OATYPE_DESTINATION, 0}, false, OA_DIJKSTRA_POLYGON_SHORTPATH_NOTSET_IDX, FLT_MAX};
_short_path_data_numpoints = 2;
// add all inclusion and exclusion fence points to short_path_data array (node_type, id, visited, distance_from_idx, distance_cm)
for (uint8_t i=0; i<total_numpoints(); i++) {
_short_path_data[_short_path_data_numpoints++] = {{AP_OAVisGraph::OATYPE_INTERMEDIATE_POINT, i}, false, OA_DIJKSTRA_POLYGON_SHORTPATH_NOTSET_IDX, FLT_MAX};
}
// start algorithm from source point
node_index current_node_idx = 0;
// update nodes visible from source point
for (uint16_t i = 0; i < _source_visgraph.num_items(); i++) {
node_index node_idx;
if (find_node_from_id(_source_visgraph[i].id2, node_idx)) {
_short_path_data[node_idx].distance_cm = _source_visgraph[i].distance_cm;
_short_path_data[node_idx].distance_from_idx = current_node_idx;
} else {
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_COULD_NOT_FIND_PATH;
return false;
}
}
// mark source node as visited
_short_path_data[current_node_idx].visited = true;
// move current_node_idx to node with lowest distance
while (find_closest_node_idx(current_node_idx)) {
// update distances to all neighbours of current node
update_visible_node_distances(current_node_idx);
// mark current node as visited
_short_path_data[current_node_idx].visited = true;
}
// extract path starting from destination
bool success = false;
node_index nidx;
if (!find_node_from_id({AP_OAVisGraph::OATYPE_DESTINATION,0}, nidx)) {
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_COULD_NOT_FIND_PATH;
return false;
}
_path_numpoints = 0;
while (true) {
if (!_path.expand_to_hold(_path_numpoints + 1)) {
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_OUT_OF_MEMORY;
return false;
}
// fail if newest node has invalid distance_from_index
if ((_short_path_data[nidx].distance_from_idx == OA_DIJKSTRA_POLYGON_SHORTPATH_NOTSET_IDX) ||
(_short_path_data[nidx].distance_cm >= FLT_MAX)) {
break;
} else {
// add node's id to path array
_path[_path_numpoints] = _short_path_data[nidx].id;
_path_numpoints++;
// we are done if node is the source
if (_short_path_data[nidx].id.id_type == AP_OAVisGraph::OATYPE_SOURCE) {
success = true;
break;
} else {
// follow node's "distance_from_idx" to previous node on path
nidx = _short_path_data[nidx].distance_from_idx;
}
}
}
// update source and destination for by get_shortest_path_point
if (success) {
_path_source = origin_NE;
_path_destination = destination_NE;
} else {
err_id = AP_OADijkstra_Error::DIJKSTRA_ERROR_COULD_NOT_FIND_PATH;
}
return success;
}
// return point from final path as an offset (in cm) from the ekf origin
bool AP_OADijkstra::get_shortest_path_point(uint8_t point_num, Vector2f& pos)
{
if ((_path_numpoints == 0) || (point_num >= _path_numpoints)) {
return false;
}
// get id from path
AP_OAVisGraph::OAItemID id = _path[_path_numpoints - point_num - 1];
// convert id to a position offset from EKF origin
switch (id.id_type) {
case AP_OAVisGraph::OATYPE_SOURCE:
pos = _path_source;
return true;
case AP_OAVisGraph::OATYPE_DESTINATION:
pos = _path_destination;
return true;
case AP_OAVisGraph::OATYPE_INTERMEDIATE_POINT:
return get_point(id.id_num, pos);
}
// we should never reach here but just in case
return false;
}