Add ability to `bake_navigation_mesh` off thread.

This feature makes it possible to workaround problems such as:
 - long baking time due to heavy synchronization when parsing geometry
   from mesh instances
 - crash when freeing `NavigationMeshInstance` while baking
 - errors when actively baking node tree is being detached from the
   scene tree

2 files changed, 9 insertions, 5 deletions

diff --git a/scene/3d/navigation_region_3d.cpp b/scene/3d/navigation_region_3d.cpp
index 7f6ecbebb7..80be770dfc 100644
--- a/scene/3d/navigation_region_3d.cpp
+++ b/scene/3d/navigation_region_3d.cpp
@@ -165,13 +165,17 @@ void _bake_navigation_mesh(void *p_user_data) {
 	}
 }
 
-void NavigationRegion3D::bake_navigation_mesh() {
+void NavigationRegion3D::bake_navigation_mesh(bool p_on_thread) {
 	ERR_FAIL_COND_MSG(bake_thread.is_started(), "Unable to start another bake request. The navigation mesh bake thread is already baking a navigation mesh.");
 
 	BakeThreadsArgs *args = memnew(BakeThreadsArgs);
 	args->nav_region = this;
 
-	bake_thread.start(_bake_navigation_mesh, args);
+	if (p_on_thread) {
+		bake_thread.start(_bake_navigation_mesh, args);
+	} else {
+		_bake_navigation_mesh(args);
+	}
 }
 
 void NavigationRegion3D::_bake_finished(Ref<NavigationMesh> p_nav_mesh) {
@@ -204,7 +208,7 @@ void NavigationRegion3D::_bind_methods() {
 
 	ClassDB::bind_method(D_METHOD("get_region_rid"), &NavigationRegion3D::get_region_rid);
 
-	ClassDB::bind_method(D_METHOD("bake_navigation_mesh"), &NavigationRegion3D::bake_navigation_mesh);
+	ClassDB::bind_method(D_METHOD("bake_navigation_mesh", "on_thread"), &NavigationRegion3D::bake_navigation_mesh, DEFVAL(true));
 	ClassDB::bind_method(D_METHOD("_bake_finished", "nav_mesh"), &NavigationRegion3D::_bake_finished);
 
 	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "navmesh", PROPERTY_HINT_RESOURCE_TYPE, "NavigationMesh"), "set_navigation_mesh", "get_navigation_mesh");
diff --git a/scene/3d/navigation_region_3d.h b/scene/3d/navigation_region_3d.h
index 1c559bc31a..140dfebf6a 100644
--- a/scene/3d/navigation_region_3d.h
+++ b/scene/3d/navigation_region_3d.h
@@ -62,9 +62,9 @@ public:
 	void set_navigation_mesh(const Ref<NavigationMesh> &p_navmesh);
 	Ref<NavigationMesh> get_navigation_mesh() const;
 
-	/// Bakes the navigation mesh in a dedicated thread; once done, automatically
+	/// Bakes the navigation mesh; once done, automatically
 	/// sets the new navigation mesh and emits a signal
-	void bake_navigation_mesh();
+	void bake_navigation_mesh(bool p_on_thread);
 	void _bake_finished(Ref<NavigationMesh> p_nav_mesh);
 
 	TypedArray<String> get_configuration_warnings() const override;