BD Derive PBR Maps

You've got a single stylized character image and you want it to light correctly in a game engine. BD Derive PBR Maps is the node that gets you from "one picture" to "albedo, normal, roughness, metallic, and AO, plus pre-packed ORM/ARM" without any 3D baking. It's heuristic - explicitly not a measurement - which sounds like a caveat and is actually the whole point: it's the fastest way to give a background character believable material response, and it's honest about where you should hand-tune.

How it works

Everything derives from the two required inputs: image and depth (from any IMAGE-typed estimator - DepthAnythingV2, Lotus, MiDaS, Metric3D; darker = closer is the convention here). The recipe:

• Roughness - high-frequency detail in the image (busy areas get rougher) via roughness_mode (default combined), boosted by optional line art / detail texture through detail_to_roughness.
• Metallic - metallic_mode defaults to off (flat metallic_default), but low_sat_high_lum catches bright, desaturated metal candidates (gold, chrome) with metallic_lum_threshold / metallic_sat_threshold. Restrict where metal can appear with metallic_zone_mask - the README's recommended pipeline feeds an accessories mask in here so only the buckle and zips go metallic.
• AO - from depth gradients (ao_strength, ao_blur).
• Normal - derived from depth gradients unless you supply an explicit normal_map (Metric3D-NormalMapPreprocessor is the recommended source), scaled by normal_strength.

Then the outputs: albedo, normal, roughness, metallic, ao, plus packed_orm and packed_arm (AO/roughness/metallic stacked into the R/G/B channels the way Unreal and Unity like them), and status.

The two optional inputs that take it from "meh" to "good enough"

• silhouette_mask (white = subject) - multiplies everything so background pixels don't pollute the maps and, crucially, keeps transparent-PNG edge garbage out. albedo_treatment (default edge_pad) extends foreground colors into the transparent border so you don't get halo bleed at UV seams.
• aux_shading_alpha - this is the secret weapon for stylized art. Feed it the alpha output of a shading pass (like the pack's skin-details GLSL shader: low alpha = highlights, high alpha = shaded zones) and shaded areas get +roughness, +AO, −metallic, and highlights get the opposite. The README says this is far more accurate than the image-only heuristic, and it's right.

Installing and wiring

ComfyUI Manager → search "BrainDead" → install, or clone + pip:

cd ComfyUI/custom_nodes
git clone https://github.com/BizaNator/ComfyUI-BrainDead
cd ComfyUI-BrainDead
pip install -r requirements.txt

Restart, then wire: character image → depth estimator → this node, with silhouette + shading alpha if you have them. The pack's own example runs all seven outputs into BD Bulk Save with one save-context so you get albedo/normal/roughness/metallic/ao/orm/arm files in a single run.

Where people get burned

The README is refreshingly blunt: these are heuristics for background characters - for hero assets you hand-tune downstream. People also forget that metallic_mode is off by default, so their "metal" reads as rough paint until they flip it on and feed a metallic_zone_mask. And if your normal map looks wrong, wire an explicit normal_map instead of arguing with normal_strength.