UV_options

UV_options (from ComfyUI-3D-MeshTool) is a settings node, not a doer. It produces a chart_options object - a bundle of parameters - that you feed into the UnwrapUV_xatlas node to control how the unwrap runs. Skip it entirely and the unwrap uses xatlas's defaults, which are fine for most meshes. Connect it and you get a hand on the steering wheel.

Every input maps one-to-one onto an xatlas.ChartOptions field, so what you see here is exactly what the C++ library exposes. There are ten of them, all sliders:

• fix_winding (BOOLEAN) - correct face winding while unwrapping
• max_boundary_length, max_chart_area - cut limits; 0 means no limit
• max_cost - overall chart-merging cost ceiling
• max_iterations - how many passes the packer does (default 1, range 1–64)
• normal_deviation_weight, normal_seam_weight, roundness_weight, straightness_weight, texture_seam_weight - the weights xatlas uses to decide where to cut and how to pack

Which ones actually matter

For a beginner, two are worth touching:

• max_iterations - bumping this from 1 toward 8–16 usually gives tighter packing on complex meshes at the cost of a little CPU time. The default of 1 is fast but not optimal.
• fix_winding - turn this on if your mesh came in with inconsistent face winding and the unwrap produces flipped islands.

The five weights are how you bias the unwrapper: raise texture_seam_weight to encourage fewer, cleaner seams for texturing, or raise straightness_weight if you want more regular charts. Don't touch them until you've seen a bad unwrap and know what you're trying to improve - defaults genuinely work.

Output

• UV_options (chart_options) - wire this into UnwrapUV_xatlas's UV_options socket.

Install

It's part of the pack:

cd ComfyUI/custom_nodes
git clone https://github.com/807502278/ComfyUI-3D-MeshTool
cd ComfyUI-3D-MeshTool
pip install -r requirements.txt

Restart ComfyUI, or install via ComfyUI Manager (search "ComfyUI-3D-MeshTool"). This node imports xatlas just to construct the options object, so the same install requirement as the unwrap applies.

Notes

The connection is optional by design - UnwrapUV_xatlas checks for a None and falls back to xatlas defaults, so you can start without this node and add it only when the default output isn't good enough. That's the right workflow: unwrap, look, and only then start tweaking weights. One quirk to expect: these are raw library parameters, so they don't have friendly unit labels and the numbers are relative weights, not absolute settings - don't expect "0.5" to mean the same thing as a similar-looking slider in Blender.