SceneTreeFTI faster access to Node children

Author: lawnjelly

scene/main/node.h

@@ -501,6 +501,13 @@ class Node : public Object {
 	Node *get_parent() const;
 	Node *find_parent(const String &p_pattern) const;
 
+	// Fast unsafe access to children, for bottleneck code.
+	// Use get_child_count() / get_child() for safe access.
+	// These are raw and include internal children.
+	// Callers *must* call `update_cached_children()` if there is a possibility cached children are not up to date.
+	void update_cached_children() const { _update_children_cache(); }
+	Span<Node *> get_cached_children() const { return data.children_cache.span(); }
+
 	Window *get_window() const;
 	Window *get_last_exclusive_window() const;
 

scene/main/scene_tree_fti.cpp

@@ -318,12 +318,16 @@ void SceneTreeFTI::_update_dirty_nodes(Node *p_node, uint32_t p_current_frame, f
 		return;
 	}
 
+	p_node->update_cached_children();
+	Span<Node *> children = p_node->get_cached_children();
+	uint32_t num_children = children.size();
+
 	// Not a Node3D.
 	// Could be e.g. a viewport or something
 	// so we should still recurse to children.
 	if (!s) {
-		for (int n = 0; n < p_node->get_child_count(); n++) {
-			_update_dirty_nodes(p_node->get_child(n), p_current_frame, p_interpolation_fraction, p_active, nullptr, p_depth + 1);
+		for (uint32_t n = 0; n < num_children; n++) {
+			_update_dirty_nodes(children.ptr()[n], p_current_frame, p_interpolation_fraction, p_active, nullptr, p_depth + 1);
 		}
 		return;
 	}
@@ -424,8 +428,8 @@ void SceneTreeFTI::_update_dirty_nodes(Node *p_node, uint32_t p_current_frame, f
 	s->_clear_dirty_bits(Node3D::DIRTY_GLOBAL_INTERPOLATED_TRANSFORM);
 
 	// Recurse to children.
-	for (int n = 0; n < p_node->get_child_count(); n++) {
-		_update_dirty_nodes(p_node->get_child(n), p_current_frame, p_interpolation_fraction, p_active, s->data.fti_global_xform_interp_set ? &s->data.global_transform_interpolated : &s->data.global_transform, p_depth + 1);
+	for (uint32_t n = 0; n < num_children; n++) {
+		_update_dirty_nodes(children.ptr()[n], p_current_frame, p_interpolation_fraction, p_active, s->data.fti_global_xform_interp_set ? &s->data.global_transform_interpolated : &s->data.global_transform, p_depth + 1);
 	}
 }