blender-mcp

# blender-mcp

An MCP server that builds Blender .blend files. It reaches Blender two ways:

• Headless — every call starts a fresh blender --background process. Deterministic, always available, and the right choice for generating files.

• Live — a small Blender addon opens a local port so the server can drive the Blender window you already have open, and you watch it happen.

Both routes run the same handler code, so a script behaves identically either way. A local web UI lets you upload reference images and run generation jobs with the same tools.

Requirements

Related MCP server: Blender MCP

Setup

uv sync                                        # create .venv and install
cp .env.example .env                           # then set BLENDER_MCP_EXECUTABLE
uv run python scripts/build_addon.py --install # build + install the Blender addon

If you skip .env, the server searches your PATH and the standard Program Files/Blender Foundation/Blender <version> folders on every drive, preferring the newest version it finds.

Turning on the live bridge

The addon is installed but idle until you start it:

1. Open Blender.

2. Press N in the 3D viewport to show the sidebar.

3. Open the MCP tab and click Start MCP Bridge.

Tick Start listening on launch in the addon preferences to skip this every time.

Connecting an MCP client

.cursor/mcp.json already registers the server for this project. To make it available everywhere, copy that block into ~/.cursor/mcp.json:

{
  "mcpServers": {
    "blender": {
      "command": "uv",
      "args": ["run", "--directory", "C:\\Users\\josef\\Projects\\blender-mcp", "blender-mcp"]
    }
  }
}

Quality workflow

Generation quality comes from looking, not from a single script dump:

1. list_references / view_reference — open guide images first

2. create_blend from studio or product

3. Build in small run_script steps; apply_material for metal/plastic/rubber/glass/wood

4. preview_views — multi-angle EEVEE previews; compare to refs with view_image

5. Fix, preview again

6. Final render / render_and_view (CYCLES only for finals; EEVEE while iterating)

Local web UI

uv run blender-mcp-web
# open http://127.0.0.1:8765

Upload reference images, enter a prompt, and browse jobs under output/jobs/.

• With BLENDER_MCP_LLM_API_KEY in .env — the site runs a bounded multimodal agent that calls the same Blender tools (OpenAI-compatible or Anthropic via BLENDER_MCP_LLM_PROVIDER).

• Without a key — uploads and job pages still work; open the job in Cursor and ask the MCP agent to build from output/jobs/<id>/refs.

Tools

Writing scripts

run_script and the script argument of create_blend execute in a namespace where bpy, mathutils, math, D (bpy.data) and C (bpy.context) are already bound. Send data back by assigning to result or calling emit(value).

Templates

Layout

addon/blender_mcp_addon/   Blender extension + shared handlers (incl. preview_views)
src/blender_mcp/
  server.py                MCP tools
  refs.py                  reference image library
  materials.py             procedural material presets
  templates.py             starter scenes
  agent/                   bounded multimodal generation loop
  web/                     FastAPI UI (templates + static)
  headless.py / bridge.py  Blender process / live socket
scripts/                   build, install, verification
output/                    .blend files, renders, refs/, jobs/

Testing

uv run pytest -m "not blender"   # fast
uv run pytest                    # includes real Blender runs
uv run python scripts/check_server.py
uv run python scripts/verify_live_bridge.py

Notes and limits

• run_script executes arbitrary Python inside Blender. Keep the bridge on loopback.

• Long renders block the live UI until they finish.

• viewport_screenshot is live-only.

• Cycles uses CPU unless you enable a GPU device in Blender preferences.

• The web agent needs a multimodal model that supports tool calls and images.

Licence

MIT