Implemented handle normal calculation, and facing checks based on them for clicking. This doesn't work well, so it will be removed, but committing it because the normal calculations might come in handy later,.

game/addons/mesh_data_resource_editor/MIDGizmo.gd

@@ -60,6 +60,7 @@ var _mdr : MeshDataResource = null
 var _vertices : PoolVector3Array
 var _indices : PoolIntArray
 var _handle_points : PoolVector3Array
+var _handle_normals : PoolVector3Array
 var _handle_to_vertex_map : Array
 var _selected_points : PoolIntArray
 
@@ -228,18 +229,26 @@ func selection_click_select_front_or_back(index, camera, event):
 		var closest_dist : float = 1e10
 					
 		for i in range(_handle_points.size()):
+			var is_dir_similar : bool = MDRMeshUtils.is_direction_similar(_handle_normals[i], _last_known_camera_facing)
+			
+			if handle_selection_type == HandleSelectionType.HANDLE_SELECTION_TYPE_FRONT:
+				if is_dir_similar:
+					continue
+			elif handle_selection_type == HandleSelectionType.HANDLE_SELECTION_TYPE_BACK:
+				if !is_dir_similar:
+					continue
+			
 			var vert_pos_3d : Vector3 = gt.xform(_handle_points[i])
 			var vert_pos_2d : Vector2 = camera.unproject_position(vert_pos_3d)
 			var dist_3d : float = ray_from.distance_to(vert_pos_3d)
 			var dist_2d : float = gpoint.distance_to(vert_pos_2d)
-						
+
 			if (dist_2d < grab_threshold && dist_3d < closest_dist):
 				closest_dist = dist_3d
 				closest_idx = i
 
 		if (closest_idx >= 0):
 			for si in range(_selected_points.size()):
-							
 				if _selected_points[si] == closest_idx:
 					if event.alt || event.control:
 						_selected_points.remove(si)
@@ -598,6 +607,7 @@ func recalculate_handle_points() -> void:
 	if !_mdr:
 		_handle_points.resize(0)
 		_handle_to_vertex_map.resize(0)
+		_handle_normals.resize(0)
 		return
 	
 	var mdr_arr : Array = _mdr.array
@@ -605,6 +615,7 @@ func recalculate_handle_points() -> void:
 	if mdr_arr.size() != ArrayMesh.ARRAY_MAX || mdr_arr[ArrayMesh.ARRAY_VERTEX] == null || mdr_arr[ArrayMesh.ARRAY_VERTEX].size() == 0:
 		_handle_points.resize(0)
 		_handle_to_vertex_map.resize(0)
+		_handle_normals.resize(0)
 		return
 	
 	var arr : Array = Array()
@@ -626,6 +637,66 @@ func recalculate_handle_points() -> void:
 		
 		_handle_points = result[0]
 		_handle_to_vertex_map = result[1]
+		
+	recalculate_handle_normals()
+
+func recalculate_handle_normals() -> void:
+	_handle_normals.resize(0)
+	var mdr_arr : Array = _mdr.array
+	
+	if mdr_arr[ArrayMesh.ARRAY_NORMAL] == null || mdr_arr[ArrayMesh.ARRAY_NORMAL].size() != mdr_arr[ArrayMesh.ARRAY_VERTEX].size():
+		recalculate_handle_normals_no_vert_normals()
+		return
+	
+	var normals : PoolVector3Array = mdr_arr[ArrayMesh.ARRAY_NORMAL]
+	
+	for i in range(_handle_points.size()):
+		var ps : PoolIntArray = _handle_to_vertex_map[i]
+		
+		if ps.size() == 0:
+			_handle_normals.push_back(Vector3())
+			continue
+		
+		var handle_normal : Vector3 = normals[ps[0]]
+		
+		for ind in range(1, ps.size()):
+			handle_normal += normals[ps[ind]]
+			
+		handle_normal /= ps.size()
+		_handle_normals.push_back(handle_normal.normalized())
+
+func recalculate_handle_normals_no_vert_normals() -> void:
+	var mdr_arr : Array = _mdr.array
+	var vertices : PoolVector3Array = mdr_arr[ArrayMesh.ARRAY_VERTEX]
+	var indices : PoolIntArray = mdr_arr[ArrayMesh.ARRAY_INDEX]
+	
+	for i in range(_handle_points.size()):
+		var ps : PoolIntArray = _handle_to_vertex_map[i]
+		
+		if ps.size() == 0:
+			_handle_normals.push_back(Vector3())
+			continue
+		
+		var handle_normal : Vector3 = Vector3()
+
+		for ind in range(ps.size()):
+			var n : Vector3 = Vector3()
+			
+			for iind in range(indices.size()):
+				var indx : int = indices[iind]
+				
+				if ind == iind:
+					var tri_start_ind : int = iind / 3
+					tri_start_ind *= 3
+					
+					var p : Plane = Plane(vertices[tri_start_ind], vertices[tri_start_ind + 1], vertices[tri_start_ind + 2])
+					
+					n += p.normal
+			
+			handle_normal += n.normalized()
+			
+		handle_normal /= ps.size()
+		_handle_normals.push_back(handle_normal.normalized())
 
 func on_mesh_data_resource_changed(mdr : MeshDataResource) -> void:
 	if _mdr:

game/addons/mesh_data_resource_editor/utilities/mdred_mesh_utils.gd

@@ -512,6 +512,10 @@ static func is_normal_similar(v0 : Vector3, v1 : Vector3, v2 : Vector3, similar_
 	
 	return ndns >= 0
 
+static func is_direction_similar(d0 : Vector3, d1 : Vector3) -> bool:
+	var ndns : float = d0.dot(d1)
+	return ndns >= 0
+
 static func flip_triangle_ti(mdr : MeshDataResource, triangle_index : int) -> void:
 	flip_triangle(mdr, triangle_index * 3)