fix: regenerate navmesh if already exists

Author: invertedEcho

src/enemy/spawn/mod.rs

@@ -8,7 +8,7 @@ use crate::{
     },
     nav_mesh_pathfinding::{ArchipelagoRef, ENEMY_AGENT_RADIUS},
 };
-use avian3d::math::PI;
+use avian3d::{math::PI, prelude::LinearVelocity};
 use bevy::prelude::*;
 use bevy_landmass::{
     Agent, Agent3dBundle, AgentSettings, AgentTarget3d, ArchipelagoRef3d,
@@ -138,6 +138,7 @@ fn handle_spawn_enemies_at_enemy_spawn_locations_message(
                                 TimerMode::Repeating,
                             )),
                             Visibility::Visible,
+                            LinearVelocity::ZERO,
                         ))
                         .with_child((
                             Transform {

src/game_flow/systems.rs

@@ -3,7 +3,7 @@ use bevy::{
     prelude::*,
     window::{CursorGrabMode, CursorOptions, PrimaryWindow},
 };
-use bevy_rerecast::prelude::NavmeshReady;
+use bevy_rerecast::{Navmesh, prelude::NavmeshReady};
 
 use crate::{
     enemy::Enemy,
@@ -12,6 +12,7 @@ use crate::{
         game_mode::StartGameModeMessage,
         states::{GameLoadingState, InGameState, SelectedMapState},
     },
+    nav_mesh_pathfinding::NavMeshHandle,
     player::{Player, camera::components::FreeCam},
     user_interface::main_menu::MainMenuCamera,
     world::resources::WorldSceneHandle,
@@ -126,11 +127,24 @@ pub fn check_collider_constructor_hierarchy_ready(
 }
 
 pub fn check_navmesh_ready(
-    _: On<NavmeshReady>,
+    trigger: On<NavmeshReady>,
+    mut commands: Commands,
     mut next_game_loading_state: ResMut<NextState<GameLoadingState>>,
+    mut nav_meshes: ResMut<Assets<Navmesh>>,
 ) {
+    let Some(nav_mesh_handle) = nav_meshes.get_strong_handle(trigger.0) else {
+        panic!(
+            "Got navmeshready event but the Handle could not be found using \
+             the asset id from the trigger"
+        );
+    };
+
     info!("Navmesh is now ready!");
     next_game_loading_state.set(GameLoadingState::NavMeshReady);
+
+    // need to store it in our own resource so we can call regenerate when a new map is selected
+    commands.insert_resource(NavMeshHandle(nav_mesh_handle));
+    info!("Stored navmesh handle in our own resource, `NavMeshHandle`");
 }
 
 pub fn on_game_loading_state_nav_mesh_ready(

src/nav_mesh_pathfinding/mod.rs

@@ -27,32 +27,46 @@ impl Plugin for NavMeshPathfindingPlugin {
     }
 }
 
+#[derive(Resource)]
+pub struct NavMeshHandle(pub Handle<Navmesh>);
+
 #[derive(Resource)]
 pub struct ArchipelagoRef(pub Entity);
 
 fn generate_navmesh_when_map_colliders_ready(
     mut commands: Commands,
     mut generator: NavmeshGenerator,
+    maybe_existing_nav_mesh: Option<Res<NavMeshHandle>>,
 ) {
-    let archipelago_id = commands
-        .spawn(Archipelago3d::new(ArchipelagoOptions::from_agent_radius(
-            ENEMY_AGENT_RADIUS,
-        )))
-        .id();
-    commands.insert_resource(ArchipelagoRef(archipelago_id));
-
-    let navmesh = generator.generate(NavmeshSettings {
+    let nav_mesh_settings = NavmeshSettings {
         agent_radius: ENEMY_AGENT_RADIUS,
         ..default()
-    });
+    };
 
-    commands.spawn(DetailNavmeshGizmo::new(&navmesh));
+    if let Some(existing_nav_mesh) = maybe_existing_nav_mesh {
+        info!("Nav mesh already exists, regenerating!");
+        generator.regenerate(&existing_nav_mesh.0, nav_mesh_settings);
+    } else {
+        let archipelago_id = commands
+            .spawn(Archipelago3d::new(ArchipelagoOptions::from_agent_radius(
+                ENEMY_AGENT_RADIUS,
+            )))
+            .id();
+        commands.insert_resource(ArchipelagoRef(archipelago_id));
 
-    commands.spawn(Island3dBundle {
-        island: Island,
-        archipelago_ref: ArchipelagoRef3d::new(archipelago_id),
-        nav_mesh: NavMeshHandle3d(navmesh),
-    });
+        let navmesh = generator.generate(NavmeshSettings {
+            agent_radius: ENEMY_AGENT_RADIUS,
+            ..default()
+        });
+
+        commands.spawn(DetailNavmeshGizmo::new(&navmesh));
+
+        commands.spawn(Island3dBundle {
+            island: Island,
+            archipelago_ref: ArchipelagoRef3d::new(archipelago_id),
+            nav_mesh: NavMeshHandle3d(navmesh),
+        });
+    }
 }
 
 fn update_agent_velocity(