BD Parts Underpaint

Once you've torn a character into parts and rebuilt each one cleanly, you still need the background they sit on - but the original background has the character in it. Remove the jacket and what should show through is the shirt or skin underneath, and nobody generated that for you. BD Parts Underpaint is the node that fabricates it: it inpaints the source image where each part was removed, revealing whatever would naturally be underneath - skin under clothing, interior under panels, background behind an object.

It's the companion to BD Parts Batch Edit and they're designed to run together: Batch Edit produces the rebuilt part renders, Underpaint produces the clean base_image (source with all parts removed), and you wire that base into BD Parts Export's base_image so the rebuilt parts composite onto the clean surface. One node strips the character away, the other rebuilds the pieces - together they reassemble the whole scene.

The two modes

• per_part_sequential (default) - one Qwen inpaint pass per part, in remove_order (outer layers first: jacket, then shirt, then pants). Each pass result feeds the next, so successive layers reveal beneath each other. Most detailed, but costs N × Qwen inference time.
• all_parts_combined - unions all part masks into one, single Qwen pass. Faster, and fine when parts don't overlap much, but large masked regions are harder for Qwen to fill coherently.

prompt_template (with {tag} interpolation) controls the language of the reveal - the defaults cover characters, vehicles, and products, and the tooltips give you ready swaps for each domain. prefill_mode (default color_spread) decides what Qwen sees before it starts: cv2 Telea inpaint fills from boundary colors, which gives the model a plausible gradient to refine; nearest-neighbor, neutral gray, and flat fills are the alternatives.

Backend choice: model_type

This is the input to read carefully, because it changes what you wire:

• qwen_edit (default) - Qwen Image Edit. Uses VLM image tokens + reference latents; wire the same model/clip/vae stack as Batch Edit.
• kontext_dev - Flux Kontext Dev (flux1-kontext-dev.safetensors + DualCLIPLoader + Flux VAE). Better real-scene coherence, per the pack.
• flux_fill - Flux Fill Dev or any plain Flux inpaint model.

Each maps to different wiring, and the full-image/edit-model guidance in the tooltips is worth heeding: full_image_pass should be ON for instruction-edit models (kontext_dev, qwen_edit) - they're designed to see the whole scene, and cropping to a part's bbox makes them hallucinate context. composite_mode=mask_region pastes only the masked region back, keeping pixels outside untouched - that's the default and the right call for inpaint models.

The other controls mirror Batch Edit (steps=4, cfg=1.0, euler, simple, shift=3, CFGNorm 0.85, tonemap 2 - all Lightning-LoRA defaults). mask_dilate_pixels (default 4, range up to 256) is the one you'll actually tune: raise it to 64–128 to eliminate edge halos when removing objects with visible outlines. remove_order and skip_tags control which parts get removed and in what sequence. Outputs: parts (passthrough), base_image, image_batch (per-step frames), and summary.

Install & expectations

In ComfyUI-BrainDead: Manager search "BrainDead", or clone + pip install -r requirements.txt. It runs a 20B edit model - budget VRAM accordingly, and keep ComfyUI on a current version (V3-API pack).

The honest caveat: sequential mode with full_image_pass on means a full-image generation per part, so a five-part character is five slow passes. That's the cost of coherence - if you're in a hurry and the parts don't overlap, all_parts_combined cuts it to one. And the quality ceiling is the edit model's: Qwen Image Edit is the 2026 default for this kind of work, but "what's under the jacket" is a genuinely hard question, so skim the per-step frames in image_batch before you trust the result in production.