Composite Nodes Guide

The pack's compositor family is big - background removal, unified background replace, layered composites, staged workflows, MediaPipe face composites - and if you've ever stared at a UC_StagedLayeredBackgroundComposite node and wondered what half its sockets do, this node is the pack's way of handing you the manual from inside the graph. It's a documentation node: pick a topic, get a Markdown string out, drop it into a markdown preview, and read while you build.

The topic dropdown is the whole interface. It starts at node_catalog - a one-line map of every compositor node and what each is for, which is genuinely the fastest way to figure out which of the eight overlapping-looking composites you actually need. Then it goes deep on the specifics: model_inputs explains the model sockets (a disconnected background_removal_model_opt loads the internal birefnet.safetensors; a connected Core BACKGROUND_REMOVAL model overrides it, which is how you'd use a Lucida model). mask_cleanup_and_resize walks the mask controls - mask_threshold, border_cleanup_width, artifact_cleanup_radius, gap_fill_radius, feather_radius, and the resize methods with their hard-vs-soft edge behavior. There are topics for the unified replace, the layered composite, both staged workflows, the placement editor, paint layers, and the MediaPipe face composite.

Why this node exists is the real story: the compositor family is where this pack stops being "a bag of utilities" and becomes a tool with opinions. Staged compositing is a multi-pass workflow - cutouts are retained in server memory between the staging run and the final composite, and you must re-stage after restarting ComfyUI because the retained cutouts don't survive a restart. That's a genuinely easy way to end up with a confusingly empty composite, and the guide's staged_workflow topic walks you through the run_staging/run_staged/full_run distinction so you understand why.

There's a parallel UC_EncoderNodesGuide for the pack's encoder and conditioning family, but the composite guide is arguably the more essential of the two, because the compositors are the part beginners actually reach for and the part with the most moving pieces. Background removal in general is the most-commoditized operation in the ecosystem (the KB's doc on it is worth reading - BiRefNet vs InSPyReNet, and why you pick by which failure you can tolerate), but turning cutouts into a placed, layered scene is a different, fiddlier problem, and this node is the cheat sheet for exactly that.

Practical tips: the output is a single markdown string - wire it into any markdown-preview node (the pack even ships UC_MarkdownPreview). It's static documentation, so nothing about it is cached or stateful; you can call it as many times as you like. And when you hit the error about a missing birefnet.safetensors, the model_inputs topic tells you precisely where the pack expects it (ComfyUI/models/background_removal/) and where to get it.

Install is pack-standard: Manager search "ComfyUI-UtilsCollection" or git clone into custom_nodes. No models needed just to read the docs - only if you actually run a removal or composite node.