Object Set Use Mesh Mirror Y

Faces are symmetric left-to-right, which is why Object Set Use Mesh Mirror X is the mirror-editing flag you'll actually use on an avatar. Object Set Use Mesh Mirror Y is the same mechanism on a different axis - and for most character work, that axis is wrong. That's not a bug; it's just Blender being Blender, and this node being honest about it. Like every ObjectSet_ node in Avatech's Avatar Graph pack, it sets one property on the Blender object on its BPY_OBJ input and passes the object back.

What it actually does

Blender's mesh mirroring has three switches - X, Y, and Z - one per axis, and each mirrors your edit-mode changes across that axis' symmetry plane. X mirrors left/right, which is the natural symmetry of a face or a body. Y mirrors front/back, which is useful for things like vehicles, tools, or any object that's symmetric between its front and back halves. Z mirrors top/bottom, for things like bowls or mushrooms. use_mesh_mirror_y is the Y toggle.

For a character avatar you almost certainly don't want Y mirroring - your character's front (face, chest) and back (hair, spine) are not symmetric, and turning this on would have your edits to the front half trying to duplicate onto the back. It defaults to false, and unlike some of these flags, the default isn't just right - it's load-bearing. The node is part of the pack because Avatar Graph auto-generates a setter for every simple Blender object attribute (the list lives in blender/ops_mesh.py), not because the avatar pipeline needs it.

The inputs and outputs that matter

• BPY_OBJ - the mesh whose mirror-editing flag you're setting.
• value - boolean, default false. true turns on Y-axis mirror editing.

Output is the same BPY_OBJ, passed on unchanged.

How to install it

Part of the Avatar Graph pack - ComfyUI Manager, search "Avatar Graph", or:

cd ComfyUI/custom_nodes
git clone https://github.com/avatechai/avatar-graph-comfyui
cd avatar-graph-comfyui
pip install -r requirements.txt

restart ComfyUI. Standard pack-level gotcha: bpy==3.6.0 only ships wheels for Python 3.10.x, so a modern-Python install fails. python=3.10 conda env on Linux/macOS, Avatech's prebuilt Python-3.10 ComfyUI zip on Windows.

Gotchas

If you enable this and your front-half edits suddenly start producing weird mirrored geometry on the character's back, that's this flag working exactly as designed - turn it back off. The realistic failure mode is the opposite: leaving it on by accident and being confused by non-face-symmetric results. It's a no-op unless you're actively editing the mesh in edit mode, so on a pure generate-and-rig pipeline you'll never see it do anything.