Fixed root node to point forwards under the hips.

addons/godot_vmc_tracker/vmc_source.gd

@@ -214,10 +214,15 @@ func _process_joints() -> void:
 		# Set the joint flags
 		_body_tracker.set_joint_flags(body, JOINT_TRACKING)
 
-	# Calculate and set the root joint under the hips
-	var root := _body_tracker.get_joint_transform(XRBodyTracker.JOINT_HIPS)
-	root.basis = Basis.IDENTITY
-	root.origin = root.origin.slide(Vector3.UP)
+	# Get the hips transform
+	var hips := _body_tracker.get_joint_transform(XRBodyTracker.JOINT_HIPS)
+
+	# Construct the root under the hips pointing forwards
+	var root_y = Vector3.UP
+	var root_z = -hips.basis.x.cross(root_y)
+	var root_x = root_y.cross(root_z)
+	var root_o := hips.origin.slide(Vector3.UP)
+	var root := Transform3D(root_x, root_y, root_z, root_o).orthonormalized()
 	_body_tracker.set_joint_transform(XRBodyTracker.JOINT_ROOT, root)
 	_body_tracker.set_joint_flags(XRBodyTracker.JOINT_ROOT, JOINT_TRACKING)
 

demo.tscn

@@ -1,4 +1,4 @@
-[gd_scene load_steps=13 format=3 uid="uid://dkkew3u3hi7md"]
+[gd_scene load_steps=14 format=3 uid="uid://dkkew3u3hi7md"]
 
 [ext_resource type="Script" path="res://demo.gd" id="1_7k4ei"]
 [ext_resource type="PackedScene" uid="uid://bhc6nngwjdvum" path="res://assets/test_chan/Test-Chan.fbx" id="1_lkeve"]
@@ -35,6 +35,11 @@ outer_radius = 0.6
 rings = 32
 ring_segments = 8
 
+[sub_resource type="SphereMesh" id="SphereMesh_t4i7x"]
+material = SubResource("StandardMaterial3D_gl6q7")
+radius = 0.05
+height = 0.2
+
 [sub_resource type="StyleBoxFlat" id="StyleBoxFlat_upoxw"]
 bg_color = Color(0, 0, 0, 0.498039)
 
@@ -119,6 +124,10 @@ transform = Transform3D(1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0.05, 0)
 mesh = SubResource("TorusMesh_rbtmk")
 skeleton = NodePath("")
 
+[node name="Forward" type="MeshInstance3D" parent="Chan/XRBodyModifier3D/GroundRing"]
+transform = Transform3D(1, -8.74228e-08, -8.74228e-08, 8.74228e-08, -4.37114e-08, 1, -8.74228e-08, -1, -4.37114e-08, -5.96046e-08, 0, -0.6)
+mesh = SubResource("SphereMesh_t4i7x")
+
 [node name="Kun" type="Node3D" parent="."]
 transform = Transform3D(-1, 0, 8.74228e-08, 0, 1, 0, -8.74228e-08, 0, -1, 0.6, 0, 0)
 
@@ -181,6 +190,10 @@ transform = Transform3D(1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0.05, 0)
 mesh = SubResource("TorusMesh_rbtmk")
 skeleton = NodePath("")
 
+[node name="Forward" type="MeshInstance3D" parent="Kun/XRBodyModifier3D/GroundRing"]
+transform = Transform3D(1, -8.74228e-08, -8.74228e-08, 8.74228e-08, -4.37114e-08, 1, -8.74228e-08, -1, -4.37114e-08, -5.96046e-08, 0, -0.6)
+mesh = SubResource("SphereMesh_t4i7x")
+
 [node name="PanelContainer" type="PanelContainer" parent="."]
 anchors_preset = 3
 anchor_left = 1.0