Object Hook Assign

In Blender's modifier panel, every Hook modifier has an Assign button. It takes the vertices you currently have selected and commits them to that hook's influence set. Object_HookAssign is that button, exposed as a node in the Avatar Graph pack - and if you're rigging an avatar, you'll probably use it more than any other hook node.

Here's the workflow it fits into. You create a hook (via Object_HookAddNewob or Object_HookAddSelob), then come back later and say "actually, these other verts should also follow that hook." Or you set up a hook that covers the wrong region and need to re-bind. That's Assign's job: it repopulates which vertices the named hook drives, based on whatever is selected right now.

How it works

It calls bpy.ops.object.hook_assign(), with one real input beyond the object:

• modifier - the name of the Hook modifier you're assigning to. This is the gotcha: the field is typed as B_ENUM, which in this pack means a plain string you supply via the ENUM (Blender) helper node. You have to type the modifier's exact name (e.g. Hook), matching what the hook-creation nodes generated. Misspelled or wrong name → the operator silently no-ops or errors.

Blender's hook operators take the modifier name rather than an index, so this string is genuinely how you pick which hook. The pack's auto-generated schemas inherit that quirk.

BPY_OBJ sets the active object in the embedded scene and passes back out unchanged - the standard pass-through for this pack. And like the other hook nodes, this is an edit-mode operator: the mesh needs to be in edit mode with the target vertices selected. Drive selection upstream with the pack's Mesh_* nodes.

When you'd use it in an avatar graph

Any time you refine a rig. The classic path: hook the whole ponytail, realize the bottom three rows of verts shouldn't follow the head bone, deselect them, re-run Assign so only the top portion is bound. It's also how you'd graft a second accessory onto an existing hook without creating a new modifier. If you've built a character with a few hooks and want them to behave, Assign is your corrective tool.

Inputs and outputs

• BPY_OBJ - the mesh whose hook you're modifying.
• modifier - the hook modifier name (feed via the pack's ENUM node, or a string).
• BPY_OBJ output - the same object, so you can keep chaining.

Installing it

Part of Avatar Graph (avatechai/avatar-graph-comfyui). ComfyUI Manager: search "Avatar Graph". Manual:

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

The pack pins bpy==3.6.0, which needs Python 3.10.x; on 3.11+ the wheel won't build and the whole pack vanishes from the node list. First launch also downloads the SAM ViT-H checkpoint (~2.5 GB) and MediaPipe models, so the first run is slow.

Common issues

"If I connect a string to modifier, nothing happens" is the #1 report - and it's because the field wants the ENUM helper, not a plain string widget, and the value has to be the exact modifier name. Also remember edit mode + selection: run Assign in object mode and it errors exactly like Blender would. The README flags this pack as a work-in-progress, so if a hook node misbehaves, check the repo for a fix before assuming it's you.