From 1e479b02946f5bc9479b489d2909831c228f4d04 Mon Sep 17 00:00:00 2001
From: detomon <simon@monoxid.ch>
Date: Fri, 27 Sep 2024 09:04:57 +0200
Subject: [PATCH] Improve performance of
 `Skeleton3D::force_update_bone_children_transforms`

---
 scene/3d/skeleton_3d.cpp | 24 +++++++++---------------
 scene/3d/skeleton_3d.h   |  1 +
 2 files changed, 10 insertions(+), 15 deletions(-)

diff --git a/scene/3d/skeleton_3d.cpp b/scene/3d/skeleton_3d.cpp
index 0bb6f30c50a..9c034735f95 100644
--- a/scene/3d/skeleton_3d.cpp
+++ b/scene/3d/skeleton_3d.cpp
@@ -471,6 +471,7 @@ void Skeleton3D::_make_modifiers_dirty() {
 }
 
 void Skeleton3D::_update_bones_nested_set() {
+	nested_set_offset_to_bone_index.resize(bones.size());
 	bone_global_pose_dirty.resize(bones.size());
 	_make_bone_global_poses_dirty();
 
@@ -490,6 +491,7 @@ int Skeleton3D::_update_bone_nested_set(int p_bone, int p_offset) {
 		span += subspan;
 	}
 
+	nested_set_offset_to_bone_index[p_offset] = p_bone;
 	bones.write[p_bone].nested_set_offset = p_offset;
 	bones.write[p_bone].nested_set_span = span;
 
@@ -1056,14 +1058,14 @@ void Skeleton3D::force_update_bone_children_transforms(int p_bone_idx) {
 	ERR_FAIL_INDEX(p_bone_idx, bone_size);
 
 	Bone *bonesptr = bones.ptrw();
-	thread_local LocalVector<int> bones_to_process;
-	bones_to_process.clear();
-	bones_to_process.push_back(p_bone_idx);
 
-	uint32_t index = 0;
-	while (index < bones_to_process.size()) {
-		int current_bone_idx = bones_to_process[index];
+	// Loop through nested set.
+	for (int offset = 0; offset < bone_size; offset++) {
+		if (!bone_global_pose_dirty[offset]) {
+			continue;
+		}
 
+		int current_bone_idx = nested_set_offset_to_bone_index[offset];
 		Bone &b = bonesptr[current_bone_idx];
 		bool bone_enabled = b.enabled && !show_rest_only;
 
@@ -1110,15 +1112,7 @@ void Skeleton3D::force_update_bone_children_transforms(int p_bone_idx) {
 		}
 #endif // _DISABLE_DEPRECATED
 
-		bone_global_pose_dirty[b.nested_set_offset] = false;
-
-		// Add the bone's children to the list of bones to be processed.
-		int child_bone_size = b.child_bones.size();
-		for (int i = 0; i < child_bone_size; i++) {
-			bones_to_process.push_back(b.child_bones[i]);
-		}
-
-		index++;
+		bone_global_pose_dirty[offset] = false;
 	}
 }
 
diff --git a/scene/3d/skeleton_3d.h b/scene/3d/skeleton_3d.h
index d5d249e4e6f..2e1bd8b8eed 100644
--- a/scene/3d/skeleton_3d.h
+++ b/scene/3d/skeleton_3d.h
@@ -186,6 +186,7 @@ private:
 	LocalVector<BonePoseBackup> bones_backup;
 
 	// Global bone pose calculation.
+	LocalVector<int> nested_set_offset_to_bone_index; // Map from Bone::nested_set_offset to bone index.
 	LocalVector<bool> bone_global_pose_dirty; // Indexable with Bone::nested_set_offset.
 	void _update_bones_nested_set();
 	int _update_bone_nested_set(int p_bone, int p_offset);