feat: Add VRM Blender addon with complete import/export functionality

- Add core VRM addon infrastructure with manifest and registration
- Add common utilities module with file system, logging, and conversion helpers
- Add human bone mapper with support for multiple rigging standards (Mixamo, MMD, Unreal, Rigify, etc.)
- Add VRM 0.x and 1.x format support with property groups and handlers
- Add editor UI panels for VRM metadata, spring bones, and MToon materials
- Add exporter with glTF2 extension support for VRM format serialization
- Add importer with scene reconstruction and armature generation
- Add MToon shader support with auto-setup and material migration
- Add spring bone physics simulation with constraint handling
- Add node constraint editor for advanced rigging control
- Add comprehensive validation and error handling with user dialogs
- Add scene watcher for real-time property synchronization
- Add workspace management and preference system
- Include Python cache files and Blender manifest configuration
- This is the initial commit establishing the complete VRM addon ecosystem for Blender

editor/vrm0/gizmo_group.py

@@ -0,0 +1,62 @@
+# SPDX-License-Identifier: MIT OR GPL-3.0-or-later
+from collections.abc import Set as AbstractSet
+
+from bpy.types import Armature, Context, GizmoGroup
+
+from ..extension import get_armature_extension
+
+
+# https://gist.github.com/FujiSunflower/09fdabc7ca991f8292657abc4ef001b0
+class Vrm0FirstPersonBoneOffsetGizmoGroup(GizmoGroup):
+    bl_idname = "VRM_GGT_vrm0_first_person_bone_offset"
+    bl_label = "First Person Bone Offset Gizmo"
+    bl_space_type = "VIEW_3D"
+    bl_region_type = "WINDOW"
+    bl_options: AbstractSet[str] = {"3D", "PERSISTENT"}
+
+    @classmethod
+    def poll(cls, context: Context) -> bool:
+        active_object = context.active_object
+        if not active_object:
+            return False
+        return active_object.type == "ARMATURE"
+
+    def setup(self, context: Context) -> None:
+        active_object = context.active_object
+        if not active_object:
+            return
+        armature_data = active_object.data
+        if not isinstance(armature_data, Armature):
+            return
+        ext = get_armature_extension(armature_data)
+        first_person = ext.vrm0.first_person
+        first_person_bone = armature_data.bones[
+            first_person.first_person_bone.bone_name
+        ]
+        gizmo = self.gizmos.new("GIZMO_GT_move_3d")
+        gizmo.target_set_prop("offset", first_person, "first_person_bone_offset")
+        gizmo.matrix_basis = first_person_bone.matrix_local
+        gizmo.draw_style = "CROSS_2D"
+        gizmo.draw_options = {"ALIGN_VIEW"}
+        gizmo.color = 1.0, 0.5, 0.0
+        gizmo.alpha = 0.5
+        gizmo.color_highlight = 1.0, 0.5, 1.0
+        gizmo.alpha_highlight = 0.5
+        gizmo.scale_basis = 0.25
+
+        self.first_person_gizmo = gizmo
+
+    def refresh(self, context: Context) -> None:
+        active_object = context.active_object
+        if not active_object:
+            return
+        armature_data = active_object.data
+        if not isinstance(armature_data, Armature):
+            return
+        ext = get_armature_extension(armature_data)
+        gizmo = self.first_person_gizmo
+        first_person = ext.vrm0.first_person
+        first_person_bone = armature_data.bones[
+            first_person.first_person_bone.bone_name
+        ]
+        gizmo.matrix_basis = first_person_bone.matrix_local