Object Vertex Group Add

Vertex groups are how Blender labels parts of a mesh with names - "left eye," "mouth," "hair" - so that weights, shape keys, and modifiers can target specific regions instead of the whole object. Object Vertex Group Add creates one of those labels: it adds a new, empty vertex group to your mesh and makes it the active group. That's the entire job, and it wraps the Blender operator bpy.ops.object.vertex_group_add().

An empty group is only useful once it has vertices in it, so this node is the first half of a two-step dance: add the group, then assign vertices to it. In the Avatar Graph pipeline that's how a character's face gets its named regions before shape keys (blinks, mouth shapes) get wired to them. The pack's own high-level workflow does this kind of grouping constantly - Object Vertex Group Assign New exists precisely because add-then-assign is so common that they made a one-step version.

It takes a single input, BPY_OBJ - the mesh that gets the new group - and returns the same object with the group attached. There's no name input on this node (the auto-generated version doesn't expose one), so the group gets a default name like "Group"; if you need a named group, this pack's other vertex-group entry points or a rename step handle that.

Because it's built on the pack's EditOps base, the node flips into Blender edit mode to run, then returns to object mode. Fine for a fresh mesh, harmless otherwise.

Install is pack-wide: ComfyUI Manager → "Avatar Graph", or git clone https://github.com/avatechai/avatar-graph-comfyui into ComfyUI/custom_nodes and pip install -r requirements.txt on Python 3.10 (bpy==3.6.0). First launch downloads the ~2.4 GB SAM model.

Troubleshooting is mostly about ordering: the group only matters to later nodes that target groups by name, and the pack resets the Blender scene at the start of every run, so a group you added last run doesn't persist - the whole graph re-runs and rebuilds. If you find yourself adding a group and then immediately assigning everything in it, skip the two-step and use Object Vertex Group Assign New, which does both in one node.