BD Blender Quad Decimate

Most decimators produce triangles, and triangles are fine for rendering but miserable for rigging and animation workflows that want clean edge loops. BD Blender Quad Decimate is the exception: it runs Blender's Un-Subdivide modifier, which collapses a quad mesh back down while preserving quad topology. No triangulation, no n-gons - just fewer, bigger quads. If you've got a 2-million-quad character and you want something a game rig can actually deform, this is the node.

Each iteration divides the face count by roughly four. The math is in the tooltips and it's worth internalizing: 1 iteration = /4, 2 = /16, 3 = /64, 4 = /256. Two iterations takes 100k quads to ~6k, which is usually the sweet spot between "recognizable" and "cheap."

The inputs that matter

• iterations (default 2) - how many un-subdivide passes. Each one ~4x reduction. This is the only real knob for most jobs.
• pre_quad_remesh (off) - the trap-avoider. Un-Subdivide requires quad topology. If your input is a triangle mesh (very common for AI-generated geometry), enable this and it runs a Blender QUAD remesh first so Un-Subdivide has something to work with. octree_depth (7) controls the quad remesh resolution - higher = more quads to start from.
• fill_holes (default true) - closes open boundaries first.

Outputs: the decimated mesh (TRIMESH), quad_obj_path (a saved quad OBJ for rigging/animation work downstream), and status.

Install and the Blender gotcha

Standard pack install:

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

(ComfyUI Manager → "BrainDead", restart; keep ComfyUI on the V3 API.) It's a Blender node, so the recurring rule: a real Blender must exist. The README says Blender is bundled - the binary isn't in the repo. The code checks lib/blender/blender-5.0.1-linux-x64, sibling packs, then /usr/bin/blender. Install Blender or the node errors with "Blender not found."

The failure mode beginners hit: feeding a triangle mesh without pre_quad_remesh, getting an error or nothing happening, and assuming the node is broken. It's not - Un-Subdivide genuinely can't work on triangles. If your mesh is triangle soup (it is, if it came from TRELLIS/Pixal3D), just flip pre_quad_remesh on. And unlike a full remesh, Un-Subdivide is destructive by design - it merges quads back along existing loops, so run it on a copy unless you're sure. Pair with BD BlenderRemesh if you need to go from soup to clean quads at a specific resolution first.