object picker

__init__.py

@@ -101,7 +101,6 @@ def add_capped_frustum(bm: bmesh.types.BMesh,
     hr = [bm.verts.new(p) for p in _apply(head_mat, _ring_positions(head_radius, tables))]
     tr = [bm.verts.new(p) for p in _apply(tail_mat, _ring_positions(tail_radius, tables))]
 
-    # Side quads
     for i in range(segs):
         nxt = (i + 1) % segs
         try:
@@ -109,7 +108,6 @@ def add_capped_frustum(bm: bmesh.types.BMesh,
         except ValueError:
             pass
 
-    # Head cap
     hcv = bm.verts.new(head_pos)
     for i in range(segs):
         try:
@@ -117,7 +115,6 @@ def add_capped_frustum(bm: bmesh.types.BMesh,
         except ValueError:
             pass
 
-    # Tail cap
     tcv = bm.verts.new(tail_pos)
     for i in range(segs):
         try:
@@ -148,7 +145,7 @@ def _end_matrices(world_mat: Matrix, bone_matrix: Matrix, bone_length: float):
       our Z = bone Y  (ring normal → along bone)
     """
     bx = bone_matrix.col[0].to_3d()
-    by = bone_matrix.col[1].to_3d()   # along bone
+    by = bone_matrix.col[1].to_3d()
     bz = bone_matrix.col[2].to_3d()
 
     orient = Matrix((
@@ -177,7 +174,8 @@ class ARMATURE_OT_build_envelope_mesh(bpy.types.Operator):
     bl_label   = "Build Envelope Mesh"
     bl_description = (
         "Convert the selected armature into an envelope-style mesh. "
-        "Object/Pose mode = posed bones | Edit mode = edit bones."
+        "If a target object is set in the panel, its mesh is replaced in place. "
+        "Otherwise a new object is created and assigned as the target."
     )
     bl_options = {'REGISTER', 'UNDO'}
 
@@ -219,17 +217,44 @@ class ARMATURE_OT_build_envelope_mesh(bpy.types.Operator):
                         bone.bone.head_radius, bone.bone.tail_radius,
                         bone.parent is None)
 
-        mesh = bpy.data.meshes.new(arm_obj.name + "_envelope_mesh")
-        bm.to_mesh(mesh)
-        bm.free()
-        mesh.update()
+        panel_props = context.scene.envelope_mesher
+        target      = panel_props.target
 
-        result_obj = bpy.data.objects.new(arm_obj.name + "_envelope", mesh)
+        if target is not None:
+            # Destructively replace the target's mesh data.
+            old_mesh      = target.data
+            new_mesh      = bpy.data.meshes.new(old_mesh.name)
+            bm.to_mesh(new_mesh)
+            bm.free()
+            new_mesh.update()
+            target.data = new_mesh
+            bpy.data.meshes.remove(old_mesh)
+        else:
+            # Create a new object and hand it back to the panel picker.
+            new_mesh = bpy.data.meshes.new(arm_obj.name + "_envelope_mesh")
+            bm.to_mesh(new_mesh)
+            bm.free()
+            new_mesh.update()
+            result_obj = bpy.data.objects.new(arm_obj.name + "_envelope", new_mesh)
             context.collection.objects.link(result_obj)
+            panel_props.target = result_obj
 
         return {'FINISHED'}
 
 
+# ---------------------------------------------------------------------------
+# Panel properties
+# ---------------------------------------------------------------------------
+
+class EnvelopeMesherProperties(bpy.types.PropertyGroup):
+    target: bpy.props.PointerProperty(
+        name="Target",
+        description="Object whose mesh will be replaced on each run. "
+                    "Leave empty to create a new object on first run.",
+        type=bpy.types.Object,
+    )
+
+
 # ---------------------------------------------------------------------------
 # Panel
 # ---------------------------------------------------------------------------
@@ -243,6 +268,10 @@ class VIEW3D_PT_armature_mesher(bpy.types.Panel):
 
     def draw(self, context):
         layout = self.layout
+        props  = context.scene.envelope_mesher
+
+        layout.prop(props, "target")
+
         op = layout.operator(
             ARMATURE_OT_build_envelope_mesh.bl_idname,
             text="Build Envelope Mesh",
@@ -255,13 +284,21 @@ class VIEW3D_PT_armature_mesher(bpy.types.Panel):
 # Registration
 # ---------------------------------------------------------------------------
 
-classes = (ARMATURE_OT_build_envelope_mesh, VIEW3D_PT_armature_mesher)
+classes = (
+    EnvelopeMesherProperties,
+    ARMATURE_OT_build_envelope_mesh,
+    VIEW3D_PT_armature_mesher,
+)
 
 def register():
     for cls in classes:
         bpy.utils.register_class(cls)
+    bpy.types.Scene.envelope_mesher = bpy.props.PointerProperty(
+        type=EnvelopeMesherProperties,
+    )
 
 def unregister():
+    del bpy.types.Scene.envelope_mesher
     for cls in reversed(classes):
         bpy.utils.unregister_class(cls)