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Merge pull request #85965 from ershn/use_heap_in_astar_path_finding

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Improve pathfinding performance by using a heap to store traversable polygons
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Rémi Verschelde 2024-09-03 11:42:48 +02:00
commit e004ae7bbe
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3 changed files with 391 additions and 84 deletions
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139
modules/navigation/nav_map.cpp
View File

@ -221,27 +221,27 @@ Vector<Vector3> NavMap::get_path(Vector3 p_origin, Vector3 p_destination, bool p
// List of all reachable navigation polys.
LocalVector<gd::NavigationPoly> navigation_polys;
navigation_polys.reserve(polygons.size() * 0.75);
navigation_polys.resize(polygons.size() + link_polygons.size());
// Add the start polygon to the reachable navigation polygons.
gd::NavigationPoly begin_navigation_poly = gd::NavigationPoly(begin_poly);
begin_navigation_poly.self_id = 0;
// Initialize the matching navigation polygon.
gd::NavigationPoly &begin_navigation_poly = navigation_polys[begin_poly->id];
begin_navigation_poly.poly = begin_poly;
begin_navigation_poly.entry = begin_point;
begin_navigation_poly.back_navigation_edge_pathway_start = begin_point;
begin_navigation_poly.back_navigation_edge_pathway_end = begin_point;
navigation_polys.push_back(begin_navigation_poly);
// List of polygon IDs to visit.
List<uint32_t> to_visit;
to_visit.push_back(0);
// Heap of polygons to travel next.
gd::Heap<gd::NavigationPoly *, gd::NavPolyTravelCostGreaterThan, gd::NavPolyHeapIndexer>
traversable_polys;
traversable_polys.reserve(polygons.size() * 0.25);
// This is an implementation of the A* algorithm.
int least_cost_id = 0;
int least_cost_id = begin_poly->id;
int prev_least_cost_id = -1;
bool found_route = false;
const gd::Polygon *reachable_end = nullptr;
real_t reachable_d = FLT_MAX;
real_t distance_to_reachable_end = FLT_MAX;
bool is_reachable = true;
while (true) {
@ -260,51 +260,57 @@ Vector<Vector3> NavMap::get_path(Vector3 p_origin, Vector3 p_destination, bool p
real_t poly_enter_cost = 0.0;
real_t poly_travel_cost = least_cost_poly.poly->owner->get_travel_cost();
if (prev_least_cost_id != -1 && (navigation_polys[prev_least_cost_id].poly->owner->get_self() != least_cost_poly.poly->owner->get_self())) {
if (prev_least_cost_id != -1 && navigation_polys[prev_least_cost_id].poly->owner->get_self() != least_cost_poly.poly->owner->get_self()) {
poly_enter_cost = least_cost_poly.poly->owner->get_enter_cost();
}
prev_least_cost_id = least_cost_id;
Vector3 pathway[2] = { connection.pathway_start, connection.pathway_end };
const Vector3 new_entry = Geometry3D::get_closest_point_to_segment(least_cost_poly.entry, pathway);
const real_t new_distance = (least_cost_poly.entry.distance_to(new_entry) * poly_travel_cost) + poly_enter_cost + least_cost_poly.traveled_distance;
const real_t new_traveled_distance = least_cost_poly.entry.distance_to(new_entry) * poly_travel_cost + poly_enter_cost + least_cost_poly.traveled_distance;
int64_t already_visited_polygon_index = navigation_polys.find(gd::NavigationPoly(connection.polygon));
// Check if the neighbor polygon has already been processed.
gd::NavigationPoly &neighbor_poly = navigation_polys[connection.polygon->id];
if (neighbor_poly.poly != nullptr) {
// If the neighbor polygon hasn't been traversed yet and the new path leading to
// it is shorter, update the polygon.
if (neighbor_poly.traversable_poly_index < traversable_polys.size() &&
new_traveled_distance < neighbor_poly.traveled_distance) {
neighbor_poly.back_navigation_poly_id = least_cost_id;
neighbor_poly.back_navigation_edge = connection.edge;
neighbor_poly.back_navigation_edge_pathway_start = connection.pathway_start;
neighbor_poly.back_navigation_edge_pathway_end = connection.pathway_end;
neighbor_poly.traveled_distance = new_traveled_distance;
neighbor_poly.distance_to_destination =
new_entry.distance_to(end_point) *
neighbor_poly.poly->owner->get_travel_cost();
neighbor_poly.entry = new_entry;
if (already_visited_polygon_index != -1) {
// Polygon already visited, check if we can reduce the travel cost.
gd::NavigationPoly &avp = navigation_polys[already_visited_polygon_index];
if (new_distance < avp.traveled_distance) {
avp.back_navigation_poly_id = least_cost_id;
avp.back_navigation_edge = connection.edge;
avp.back_navigation_edge_pathway_start = connection.pathway_start;
avp.back_navigation_edge_pathway_end = connection.pathway_end;
avp.traveled_distance = new_distance;
avp.entry = new_entry;
// Update the priority of the polygon in the heap.
traversable_polys.shift(neighbor_poly.traversable_poly_index);
}
} else {
// Add the neighbor polygon to the reachable ones.
gd::NavigationPoly new_navigation_poly = gd::NavigationPoly(connection.polygon);
new_navigation_poly.self_id = navigation_polys.size();
new_navigation_poly.back_navigation_poly_id = least_cost_id;
new_navigation_poly.back_navigation_edge = connection.edge;
new_navigation_poly.back_navigation_edge_pathway_start = connection.pathway_start;
new_navigation_poly.back_navigation_edge_pathway_end = connection.pathway_end;
new_navigation_poly.traveled_distance = new_distance;
new_navigation_poly.entry = new_entry;
navigation_polys.push_back(new_navigation_poly);
// Initialize the matching navigation polygon.
neighbor_poly.poly = connection.polygon;
neighbor_poly.back_navigation_poly_id = least_cost_id;
neighbor_poly.back_navigation_edge = connection.edge;
neighbor_poly.back_navigation_edge_pathway_start = connection.pathway_start;
neighbor_poly.back_navigation_edge_pathway_end = connection.pathway_end;
neighbor_poly.traveled_distance = new_traveled_distance;
neighbor_poly.distance_to_destination =
new_entry.distance_to(end_point) *
neighbor_poly.poly->owner->get_travel_cost();
neighbor_poly.entry = new_entry;
// Add the neighbor polygon to the polygons to visit.
to_visit.push_back(navigation_polys.size() - 1);
// Add the polygon to the heap of polygons to traverse next.
traversable_polys.push(&neighbor_poly);
}
}
}
// Removes the least cost polygon from the list of polygons to visit so we can advance.
to_visit.erase(least_cost_id);
// When the list of polygons to visit is empty at this point it means the End Polygon is not reachable
if (to_visit.size() == 0) {
// When the heap of traversable polygons is empty at this point it means the end polygon is
// unreachable.
if (traversable_polys.is_empty()) {
// Thus use the further reachable polygon
ERR_BREAK_MSG(is_reachable == false, "It's not expect to not find the most reachable polygons");
is_reachable = false;
@ -366,13 +372,12 @@ Vector<Vector3> NavMap::get_path(Vector3 p_origin, Vector3 p_destination, bool p
return path;
}
// Reset open and navigation_polys
gd::NavigationPoly np = navigation_polys[0];
navigation_polys.clear();
navigation_polys.push_back(np);
to_visit.clear();
to_visit.push_back(0);
least_cost_id = 0;
for (gd::NavigationPoly &nav_poly : navigation_polys) {
nav_poly.poly = nullptr;
}
navigation_polys[begin_poly->id].poly = begin_poly;
least_cost_id = begin_poly->id;
prev_least_cost_id = -1;
reachable_end = nullptr;
@ -380,26 +385,14 @@ Vector<Vector3> NavMap::get_path(Vector3 p_origin, Vector3 p_destination, bool p
continue;
}
// Find the polygon with the minimum cost from the list of polygons to visit.
least_cost_id = -1;
real_t least_cost = FLT_MAX;
for (List<uint32_t>::Element *element = to_visit.front(); element != nullptr; element = element->next()) {
gd::NavigationPoly *np = &navigation_polys[element->get()];
real_t cost = np->traveled_distance;
cost += (np->entry.distance_to(end_point) * np->poly->owner->get_travel_cost());
if (cost < least_cost) {
least_cost_id = np->self_id;
least_cost = cost;
}
}
// Pop the polygon with the lowest travel cost from the heap of traversable polygons.
least_cost_id = traversable_polys.pop()->poly->id;
ERR_BREAK(least_cost_id == -1);
// Stores the further reachable end polygon, in case our goal is not reachable.
// Store the farthest reachable end polygon in case our goal is not reachable.
if (is_reachable) {
real_t d = navigation_polys[least_cost_id].entry.distance_to(p_destination);
if (reachable_d > d) {
reachable_d = d;
real_t distance = navigation_polys[least_cost_id].entry.distance_to(p_destination);
if (distance_to_reachable_end > distance) {
distance_to_reachable_end = distance;
reachable_end = navigation_polys[least_cost_id].poly;
}
}
@ -943,29 +936,30 @@ void NavMap::sync() {
}
// Resize the polygon count.
int count = 0;
int polygon_count = 0;
for (const NavRegion *region : regions) {
if (!region->get_enabled()) {
continue;
}
count += region->get_polygons().size();
polygon_count += region->get_polygons().size();
}
polygons.resize(count);
polygons.resize(polygon_count);
// Copy all region polygons in the map.
count = 0;
polygon_count = 0;
for (const NavRegion *region : regions) {
if (!region->get_enabled()) {
continue;
}
const LocalVector<gd::Polygon> &polygons_source = region->get_polygons();
for (uint32_t n = 0; n < polygons_source.size(); n++) {
polygons[count + n] = polygons_source[n];
polygons[polygon_count] = polygons_source[n];
polygons[polygon_count].id = polygon_count;
polygon_count++;
}
count += region->get_polygons().size();
}
_new_pm_polygon_count = polygons.size();
_new_pm_polygon_count = polygon_count;
// Group all edges per key.
HashMap<gd::EdgeKey, Vector<gd::Edge::Connection>, gd::EdgeKey> connections;
@ -1136,6 +1130,7 @@ void NavMap::sync() {
// If we have both a start and end point, then create a synthetic polygon to route through.
if (closest_start_polygon && closest_end_polygon) {
gd::Polygon &new_polygon = link_polygons[link_poly_idx++];
new_polygon.id = polygon_count++;
new_polygon.owner = link;
new_polygon.edges.clear();

176
modules/navigation/nav_utils.h
View File

@ -98,6 +98,9 @@ struct Edge {
};
struct Polygon {
/// Id of the polygon in the map.
uint32_t id = UINT32_MAX;
/// Navigation region or link that contains this polygon.
const NavBase *owner = nullptr;
@ -111,9 +114,11 @@ struct Polygon {
};
struct NavigationPoly {
uint32_t self_id = 0;
/// This poly.
const Polygon *poly;
const Polygon *poly = nullptr;
/// Index in the heap of traversable polygons.
uint32_t traversable_poly_index = UINT32_MAX;
/// Those 4 variables are used to travel the path backwards.
int back_navigation_poly_id = -1;
@ -123,20 +128,44 @@ struct NavigationPoly {
/// The entry position of this poly.
Vector3 entry;
/// The distance to the destination.
/// The distance traveled until now (g cost).
real_t traveled_distance = 0.0;
/// The distance to the destination (h cost).
real_t distance_to_destination = 0.0;
NavigationPoly() { poly = nullptr; }
NavigationPoly(const Polygon *p_poly) :
poly(p_poly) {}
bool operator==(const NavigationPoly &other) const {
return poly == other.poly;
/// The total travel cost (f cost).
real_t total_travel_cost() const {
return traveled_distance + distance_to_destination;
}
bool operator!=(const NavigationPoly &other) const {
return !operator==(other);
bool operator==(const NavigationPoly &p_other) const {
return poly == p_other.poly;
}
bool operator!=(const NavigationPoly &p_other) const {
return !(*this == p_other);
}
};
struct NavPolyTravelCostGreaterThan {
// Returns `true` if the travel cost of `a` is higher than that of `b`.
bool operator()(const NavigationPoly *p_poly_a, const NavigationPoly *p_poly_b) const {
real_t f_cost_a = p_poly_a->total_travel_cost();
real_t h_cost_a = p_poly_a->distance_to_destination;
real_t f_cost_b = p_poly_b->total_travel_cost();
real_t h_cost_b = p_poly_b->distance_to_destination;
if (f_cost_a != f_cost_b) {
return f_cost_a > f_cost_b;
} else {
return h_cost_a > h_cost_b;
}
}
};
struct NavPolyHeapIndexer {
void operator()(NavigationPoly *p_poly, uint32_t p_heap_index) const {
p_poly->traversable_poly_index = p_heap_index;
}
};
@ -146,6 +175,129 @@ struct ClosestPointQueryResult {
RID owner;
};
template <typename T>
struct NoopIndexer {
void operator()(const T &p_value, uint32_t p_index) {}
};
/**
* A max-heap implementation that notifies of element index changes.
*/
template <typename T, typename LessThan = Comparator<T>, typename Indexer = NoopIndexer<T>>
class Heap {
LocalVector<T> _buffer;
LessThan _less_than;
Indexer _indexer;
public:
void reserve(uint32_t p_size) {
_buffer.reserve(p_size);
}
uint32_t size() const {
return _buffer.size();
}
bool is_empty() const {
return _buffer.is_empty();
}
void push(const T &p_element) {
_buffer.push_back(p_element);
_indexer(p_element, _buffer.size() - 1);
_shift_up(_buffer.size() - 1);
}
T pop() {
ERR_FAIL_COND_V_MSG(_buffer.is_empty(), T(), "Can't pop an empty heap.");
T value = _buffer[0];
_indexer(value, UINT32_MAX);
if (_buffer.size() > 1) {
_buffer[0] = _buffer[_buffer.size() - 1];
_indexer(_buffer[0], 0);
_buffer.remove_at(_buffer.size() - 1);
_shift_down(0);
} else {
_buffer.remove_at(_buffer.size() - 1);
}
return value;
}
/**
* Update the position of the element in the heap if necessary.
*/
void shift(uint32_t p_index) {
ERR_FAIL_UNSIGNED_INDEX_MSG(p_index, _buffer.size(), "Heap element index is out of range.");
if (!_shift_up(p_index)) {
_shift_down(p_index);
}
}
void clear() {
for (const T &value : _buffer) {
_indexer(value, UINT32_MAX);
}
_buffer.clear();
}
Heap() {}
Heap(const LessThan &p_less_than) :
_less_than(p_less_than) {}
Heap(const Indexer &p_indexer) :
_indexer(p_indexer) {}
Heap(const LessThan &p_less_than, const Indexer &p_indexer) :
_less_than(p_less_than), _indexer(p_indexer) {}
private:
bool _shift_up(uint32_t p_index) {
T value = _buffer[p_index];
uint32_t current_index = p_index;
uint32_t parent_index = (current_index - 1) / 2;
while (current_index > 0 && _less_than(_buffer[parent_index], value)) {
_buffer[current_index] = _buffer[parent_index];
_indexer(_buffer[current_index], current_index);
current_index = parent_index;
parent_index = (current_index - 1) / 2;
}
if (current_index != p_index) {
_buffer[current_index] = value;
_indexer(value, current_index);
return true;
} else {
return false;
}
}
bool _shift_down(uint32_t p_index) {
T value = _buffer[p_index];
uint32_t current_index = p_index;
uint32_t child_index = 2 * current_index + 1;
while (child_index < _buffer.size()) {
if (child_index + 1 < _buffer.size() &&
_less_than(_buffer[child_index], _buffer[child_index + 1])) {
child_index++;
}
if (_less_than(_buffer[child_index], value)) {
break;
}
_buffer[current_index] = _buffer[child_index];
_indexer(_buffer[current_index], current_index);
current_index = child_index;
child_index = 2 * current_index + 1;
}
if (current_index != p_index) {
_buffer[current_index] = value;
_indexer(value, current_index);
return true;
} else {
return false;
}
}
};
} // namespace gd
#endif // NAV_UTILS_H

160
tests/servers/test_navigation_server_3d.h
View File

@ -31,6 +31,7 @@
#ifndef TEST_NAVIGATION_SERVER_3D_H
#define TEST_NAVIGATION_SERVER_3D_H
#include "modules/navigation/nav_utils.h"
#include "scene/3d/mesh_instance_3d.h"
#include "scene/resources/3d/primitive_meshes.h"
#include "servers/navigation_server_3d.h"
@ -61,6 +62,32 @@ static inline Array build_array(Variant item, Targs... Fargs) {
return a;
}
struct GreaterThan {
bool operator()(int p_a, int p_b) const { return p_a > p_b; }
};
struct CompareArrayValues {
const int *array;
CompareArrayValues(const int *p_array) :
array(p_array) {}
bool operator()(uint32_t p_index_a, uint32_t p_index_b) const {
return array[p_index_a] < array[p_index_b];
}
};
struct RegisterHeapIndexes {
uint32_t *indexes;
RegisterHeapIndexes(uint32_t *p_indexes) :
indexes(p_indexes) {}
void operator()(uint32_t p_vector_index, uint32_t p_heap_index) {
indexes[p_vector_index] = p_heap_index;
}
};
TEST_SUITE("[Navigation]") {
TEST_CASE("[NavigationServer3D] Server should be empty when initialized") {
NavigationServer3D *navigation_server = NavigationServer3D::get_singleton();
@ -788,6 +815,139 @@ TEST_SUITE("[Navigation]") {
CHECK_EQ(navigation_mesh->get_vertices().size(), 0);
}
*/
TEST_CASE("[Heap] size") {
gd::Heap<int> heap;
CHECK(heap.size() == 0);
heap.push(0);
CHECK(heap.size() == 1);
heap.push(1);
CHECK(heap.size() == 2);
heap.pop();
CHECK(heap.size() == 1);
heap.pop();
CHECK(heap.size() == 0);
}
TEST_CASE("[Heap] is_empty") {
gd::Heap<int> heap;
CHECK(heap.is_empty() == true);
heap.push(0);
CHECK(heap.is_empty() == false);
heap.pop();
CHECK(heap.is_empty() == true);
}
TEST_CASE("[Heap] push/pop") {
SUBCASE("Default comparator") {
gd::Heap<int> heap;
heap.push(2);
heap.push(7);
heap.push(5);
heap.push(3);
heap.push(4);
CHECK(heap.pop() == 7);
CHECK(heap.pop() == 5);
CHECK(heap.pop() == 4);
CHECK(heap.pop() == 3);
CHECK(heap.pop() == 2);
}
SUBCASE("Custom comparator") {
GreaterThan greaterThan;
gd::Heap<int, GreaterThan> heap(greaterThan);
heap.push(2);
heap.push(7);
heap.push(5);
heap.push(3);
heap.push(4);
CHECK(heap.pop() == 2);
CHECK(heap.pop() == 3);
CHECK(heap.pop() == 4);
CHECK(heap.pop() == 5);
CHECK(heap.pop() == 7);
}
SUBCASE("Intermediate pops") {
gd::Heap<int> heap;
heap.push(0);
heap.push(3);
heap.pop();
heap.push(1);
heap.push(2);
CHECK(heap.pop() == 2);
CHECK(heap.pop() == 1);
CHECK(heap.pop() == 0);
}
}
TEST_CASE("[Heap] shift") {
int values[] = { 5, 3, 6, 7, 1 };
uint32_t heap_indexes[] = { 0, 0, 0, 0, 0 };
CompareArrayValues comparator(values);
RegisterHeapIndexes indexer(heap_indexes);
gd::Heap<uint32_t, CompareArrayValues, RegisterHeapIndexes> heap(comparator, indexer);
heap.push(0);
heap.push(1);
heap.push(2);
heap.push(3);
heap.push(4);
// Shift down: 6 -> 2
values[2] = 2;
heap.shift(heap_indexes[2]);
// Shift up: 5 -> 8
values[0] = 8;
heap.shift(heap_indexes[0]);
CHECK(heap.pop() == 0);
CHECK(heap.pop() == 3);
CHECK(heap.pop() == 1);
CHECK(heap.pop() == 2);
CHECK(heap.pop() == 4);
CHECK(heap_indexes[0] == UINT32_MAX);
CHECK(heap_indexes[1] == UINT32_MAX);
CHECK(heap_indexes[2] == UINT32_MAX);
CHECK(heap_indexes[3] == UINT32_MAX);
CHECK(heap_indexes[4] == UINT32_MAX);
}
TEST_CASE("[Heap] clear") {
uint32_t heap_indexes[] = { 0, 0, 0, 0 };
RegisterHeapIndexes indexer(heap_indexes);
gd::Heap<uint32_t, Comparator<uint32_t>, RegisterHeapIndexes> heap(indexer);
heap.push(0);
heap.push(2);
heap.push(1);
heap.push(3);
heap.clear();
CHECK(heap.size() == 0);
CHECK(heap_indexes[0] == UINT32_MAX);
CHECK(heap_indexes[1] == UINT32_MAX);
CHECK(heap_indexes[2] == UINT32_MAX);
CHECK(heap_indexes[3] == UINT32_MAX);
}
}
} //namespace TestNavigationServer3D