Blender Finisher

Rough mesh → measured game-ready asset. An MCP server with a ruler.

Point an LLM at a dense, generated mesh and get back a budgeted, baked, importable game asset — where every step that cannot be proven to preserve the form is reverted.

Package name is niua-blender-mcp; the product is the finisher. New here? Read START_HERE.md — one page, then come back.

What makes it different

Most Blender integrations answer “can an LLM drive Blender?” — that is strata ①–②, and this repo has one of the larger ones. What it adds is stratum ③: eyes. The agent can look at what it just did — silhouette, wireframe density, UV stretch, a lit turntable — instead of driving blind and hoping.

That last row is deliberate. An earlier version shipped an opinionated finisher — triangle budgets per asset class, readiness gates, a retopo recipe. It is still in this repo and still runs under scripts/, but it is not in the release, because it is not good enough to stand behind: the reducer hits budget on simple props and cannot take a dense character there without wrecking it. A tool that fails on the hard case makes the whole MCP look broken when the Blender surface underneath is fine.

So the released MCP does not decide anything for you. modifiers.add with a DECIMATE modifier does exactly what it does in Blender; how far to take it is the agent's call, and the eyes are there to check the answer.

Status of the held-back layer: src/niua_blender_mcp/finishing/, domains/policy/, and the benchmark under evals/. It ships when a dense character survives the round trip. See ARCHITECTURE.md.

Related MCP server: BlenderMCP

Install

Let your agent do it

Paste this into Claude Code, Cursor, or any coding agent with shell access:

Install the Blender Finisher MCP server here. Follow these steps in order and STOP and
report if any check fails — do not improvise around a failure.

1. Check prerequisites:  `blender --version` (need 4.0+) and `python --version` (need 3.11+).
   If Blender is missing, stop and tell me how to install it for this OS.

2. Clone and install the server:
     git clone https://github.com/OhaoTech/niua-blender-mcp && cd niua-blender-mcp
     python -m pip install -e .

3. Install the Blender add-on (this asks Blender where its add-ons live, so no guessing):
     python scripts/install_addon.py
   Expect "add-on symlinked" (or "copied") and "__init__.py present = True".

4. Start the bridge. Blender must be VISIBLE, not headless — quality measurement needs
   OpenGL, and headless runs will revert finishing moves instead of passing them blind:
     blender --python scripts/blender_gui.py -- ./blender_addon 8765
   (Or open Blender normally → Preferences → Add-ons → enable "Niua MCP Bridge" →
   press N in the viewport → Niua tab → Start.)

5. Verify the bridge is alive:
     python scripts/bridge_call.py 8765 system.health '{}'
   Expect {"bridge": "alive", ...}. If not, report the exact error and stop.

6. Register the MCP server in my client config:
     {"mcpServers": {"blender-finisher": {"command": "python",
                                          "args": ["-m", "niua_blender_mcp"]}}}

7. Confirm the tool surface loaded — around 305 tools across domains including
   mesh, object, uv, shading, modifiers, io and feedback.

Then tell me: Blender version, whether the add-on is symlinked or copied, and the
health-check output.

Or by hand

python -m pip install -e .          # 1. server
python scripts/install_addon.py     # 2. add-on → Blender's add-ons dir
                                    # 3. enable "Niua MCP Bridge" in Preferences → Add-ons
python scripts/bridge_call.py 8765 system.health '{}'   # 4. verify

Then finish the benchmark fixtures:

python scripts/run_skill.py --skill bake_and_finish --port 8765 --outdir /tmp/niua_finish

install_addon.py supports --copy, --blender /path/to/blender, and --uninstall.

Status — honest

Pre-1.0. Latest acceptance run (full report), objective benchmark against real generator meshes:

Two open issues, stated plainly: real_character holds form beautifully (fidelity 0.990) but no current reducer can take it to budget without destroying it — both paths scored ~0.3 and were reverted, so it ships 4× over budget or not at all. And real_prop timed out in feedback.readiness, which left it unmeasured and correctly invalidated the run's grade.

Those numbers exist because the ruler exists. The claim worth attention is not the score — it is that the tool can tell you at all, and reverts what it cannot prove instead of shipping it.

Layout

▪ ships · ▫ stays in the repo (policy, harness, evidence)

START_HERE.md                 ← read this first
▪ src/niua_blender_mcp/       ← MCP server (Apache-2.0, never imports bpy)
▪   bridge.py / server.py       MCP ↔ Blender socket
▪   domains/                    the tool surface, minus policy/
▫   domains/policy/             budgets, gates, retopo/LOD/collision recipes
▫   finishing/                  asset classes + the finisher skills
▫   evals/                      benchmark harness (fixtures ~72 MB, untracked)
▪ blender_addon/niua_mcp_bridge/ ← Blender add-on (GPL-3.0, imports bpy)
▪   domains/eyes.py               the eyes: topology, UV checker, wire-shaded
▪   domains/objects.py            create, transform, shrinkwrap, bake_transfer
▫   domains/policy/ · finishing/  same held-back layer, add-on side
▫ tests/ · scripts/           ← how we prove it works
▫ docs/reports/               ← what we proved, and when
▫ docs/superpowers/           ← ARCHIVE (old plans) — do not start here

The split is enforced, not just described. Domains are discovered by module presence, so an artifact without domains/policy/ is one where those tools do not exist — there is no flag to forget. CI builds both artifacts and fails if a policy file appears in either; tests/test_product_surface.py fails if a policy tool is ever registered from a module that ships. Build the release add-on yourself with:

python scripts/build_addon_zip.py                 # the pure MCP (62 files)
python scripts/build_addon_zip.py --include-policy # dev build, everything

Develop

NIUA_SKIP_BLENDER=1 python -m pytest -q   # unit only
python -m pytest -q                       # + smoke if blender is installed

Three invariants are enforced by the test suite: the interface never imports finishing, the server never imports bpy, and every server tool has a matching add-on handler.

Optional: the export check imports the finished .glb into a headless game engine to prove it loads outside Blender — it uses a godot binary if one is on PATH purely as a reference importer, and reports unmeasured (never a fake pass) when none is found. The finisher itself has no engine dependency.

Security

system.execute_python is off by default; the bridge is localhost-only. Enable Python only for trusted local sessions (NIUA_BLENDER_MCP_ALLOW_PYTHON=1, or the N-panel toggle).

License

Two programs, two licenses, split on a real process boundary:

The add-on calls bpy, so Blender's GPL applies to it; the server is a separate process that talks over a socket and is permissively licensed. See LICENSING.md.

Deeper docs

• ARCHITECTURE.md — the four strata and the loop

• LICENSING.md — why the server is Apache-2.0 and the add-on is GPL

• docs/reports/ — live run evidence, including the honest failures

• docs/DESIGN.md — original full design (historical)