Add Add Center of Gravity feature

mmd_uuunyaa_tools/__init__.py

@@ -27,7 +27,7 @@
     'name': 'mmd_uuunyaa_tools',
     'description': 'Utility tools for MMD model & scene editing by Uuu(/>ω<)/Nyaa!.',
     'author': 'UuuNyaa',
-    'version': (1, 4, 0),
+    'version': (1, 5, 0),
     'blender': (2, 83, 0),
     'warning': '',
     'location': 'View3D > Sidebar > MMD Tools Panel',

mmd_uuunyaa_tools/generators/physics.py

@@ -0,0 +1,58 @@
+# -*- coding: utf-8 -*-
+# Copyright 2022 UuuNyaa <[email protected]>
+# This file is part of MMD UuuNyaa Tools.
+
+from typing import List
+
+import bpy
+from mmd_uuunyaa_tools.m17n import _
+
+
+class AddCenterOfGravityObject(bpy.types.Operator):
+    bl_idname = 'mmd_uuunyaa_tools.add_center_of_gravity_object'
+    bl_label = _('Add Center of Gravity')
+    bl_options = {'REGISTER', 'UNDO'}
+
+    radius: bpy.props.FloatProperty(name=_('Radius'), default=0.1, min=0.0, precision=4, unit='LENGTH')
+
+    @classmethod
+    def poll(cls, context: bpy.types.Context):
+        return context.mode == 'POSE' and len(context.selected_pose_bones) > 0
+
+    def execute(self, context: bpy.types.Context):
+        armature_object: bpy.types.Object = context.active_object
+        selected_pose_bones: List[bpy.types.PoseBone] = context.selected_pose_bones
+
+        center_object: bpy.types.Object = bpy.data.objects.new('EMPTY', None)
+        center_object.name = 'CenterOfGravity'
+        center_object.empty_display_type = 'PLAIN_AXES'
+        center_object.empty_display_size = self.radius
+        center_object.show_in_front = True
+        context.view_layer.active_layer_collection.collection.objects.link(center_object)
+
+        total_bone_length = sum([b.length for b in selected_pose_bones])
+
+        for pose_bone in selected_pose_bones:
+            constraint: bpy.types.CopyLocationConstraint = center_object.constraints.new('COPY_LOCATION')
+            constraint.name = f'CenterOfGravity.{pose_bone.name}'
+            constraint.target = armature_object
+            constraint.subtarget = pose_bone.name
+            constraint.head_tail = 0.5
+            constraint.use_offset = True
+            constraint.influence = pose_bone.length / total_bone_length
+
+        floor_object: bpy.types.Object = bpy.data.objects.new('EMPTY', None)
+        floor_object.name = 'CenterOfGravityOnFloor'
+        floor_object.parent = center_object
+        floor_object.empty_display_type = 'SPHERE'
+        floor_object.empty_display_size = self.radius
+        floor_object.show_in_front = True
+        context.view_layer.active_layer_collection.collection.objects.link(floor_object)
+
+        constraint: bpy.types.CopyLocationConstraint = floor_object.constraints.new('COPY_LOCATION')
+        constraint.target = armature_object
+        constraint.use_x = False
+        constraint.use_y = False
+        constraint.use_z = True
+
+        return {'FINISHED'}