io.github.kumoproductions/mcp-cinema4d MCP Server

mcp-cinema4d

Let an LLM drive Cinema 4D. mcp-cinema4d bridges MCP-compatible clients (Claude Desktop, Claude Code, or any other stdio-capable MCP client) to a running Cinema 4D 2026 session so the model can inspect scene hierarchy, author shots, build node materials, and rig animation through a typed, undo-safe tool layer — not arbitrary Python pasted into a Script Manager.

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[!IMPORTANT] Cinema 4D now ships an official MCP server. From Cinema 4D 2026.4, Maxon builds an MCP server into Cinema 4D itself: nothing to install, set up from Preferences → MCP, and supported by Maxon. If you run 2026.4 or later and simply want an AI assistant in Cinema 4D, start there — see Maxon's MCP Server page and documentation.

mcp-cinema4d is an independent community project. It remains an option where the built-in server does not fit:

• Cinema 4D 2026.0–2026.3, which have no built-in server.
• Several Cinema 4D processes from one session (multi-instance mode), which the built-in server's documentation does not cover.
• Open source — read, audit, or extend the tools and the bridge yourself.

Do not register both servers in the same client. Their tool sets overlap (both expose exec_python, for example), so the model is offered two competing sets of Cinema 4D tools. Maxon's FAQ likewise asks you to switch third-party servers off while you use the built-in one.

Good for:

• Scene audits — "List every object on the hero layer; flag any with non-uniform scale or missing Texture tags."
• Shot setup — "Create a 1920×1080 RenderData, a camera at (0, 150, -400), and a Take that uses both."
• Material work — "Build a Redshift node material with a noise texture driving roughness at 0.4 gain."
• Procedural edits — "On every Subdivision Surface in the scene, reduce editor/render levels by 1."
• Xpresso rigs — "Build a 3-gear meshing rig where the master gear's pitch radius dynamically drives the others' size and counter-rotation via an Xpresso graph."

[!CAUTION] Do not proceed unless you understand what this does. An LLM with a live connection to Cinema 4D can read your scene, write to it, and (if you opt in) execute arbitrary code on your machine. In concrete terms:

1. Your scene data leaves your machine. Object names, hierarchy paths, material/parameter values, imported file paths — whatever the LLM reads via list_entities / describe / get_container / dump_shader / get_mesh — is forwarded to your chosen LLM provider and may be logged by your MCP client. Under NDA or on unreleased IP? Confirm with your studio/legal team first that the provider's retention policy and your client's logs are acceptable.
2. The LLM gets write access. It can create, mutate, and delete objects, tags, materials, takes, render data, and layers; import / merge / open / save files; and render. Ctrl/Cmd-Z covers most edits — save_document, open_document, render, and some call_command invocations do not.
3. Arbitrary Python is off by default. exec_python runs unrestricted code with the full authority of the Cinema 4D process (file I/O, subprocess, network). Enabled only when C4D_MCP_ENABLE_EXEC_PYTHON=1 is set on both sides; turn it back off when you no longer need it. The same applies to plugin types that store Python source in their container — Python tag, Python generator, MoGraph Python effector, Python field, and the Xpresso Python operator. Creating or editing them is gated behind a separate C4D_MCP_ENABLE_PYTHON_OPS=1 opt-in, since their code parameter is RCE-equivalent to exec_python.

Before first use: back up (or commit) your scene, start on a throwaway project, and leave your MCP client's per-call approval prompts enabled. See Security before exposing the bridge beyond loopback.

Architecture

MCP client
   ↓ stdio
MCP server  (this repo, Node.js)
   ↓ TCP, JSON Lines (default 127.0.0.1:18710)
cinema4d_mcp_bridge  (Python plugin inside C4D)
   ↓
Cinema 4D

Two pieces to install: the MCP server (this npm package, runs as an MCP stdio process) and the bridge plugin (Python, lives inside Cinema 4D). C4D must be running for the bridge to respond.

Quickstart

Assuming you already have Cinema 4D 2026.0.0+ and Node.js 24+.

1. Install the bridge plugin into Cinema 4D (one-off). Download the latest cinema4d_mcp_bridge-<version>.zip from the Releases page and extract the cinema4d_mcp_bridge/ folder into your Cinema 4D plugins directory (see Installing the bridge plugin for platform-specific paths).

2. Launch (or restart) Cinema 4D. The C4D console should print [cinema4d_mcp_bridge] listening on 127.0.0.1:18710.

3. Smoke-test the MCP server from the CLI:

   echo '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"ping","arguments":{}}}' \
     | npx -y @kumoproductions/mcp-cinema4d
   #   → {"jsonrpc":"2.0","id":1,"result":{"content":[{"type":"text","text":"{\"pong\": true, ...}"}]}}
   

Then wire it into your MCP client (see Client configuration) and try:

"List every object in the scene, then add a cube named hero 200 units above the origin."

The LLM will call list_entities → create_entity in sequence; you should see a new cube appear in the viewport.

Prefer running from a local checkout? See CONTRIBUTING.md for the source-install flow.

Client configuration

Generate a random token and set it on both the MCP server process (via the client's env map, below) and the Cinema 4D launch environment. The bridge rejects mismatched requests (constant-time compare); the Node client forwards the value automatically. Strongly recommended — localhost is not a trust boundary on a shared workstation.

openssl rand -hex 16

Register the MCP server in your client with the token in the env map:

{
  "mcpServers": {
    "cinema4d": {
      "command": "npx",
      "args": ["-y", "@kumoproductions/mcp-cinema4d"],
      "env": {
        "C4D_MCP_TOKEN": "paste-your-random-hex-here"
      }
    }
  }
}

The same C4D_MCP_* variables must also be set in the Cinema 4D launch environment — the bridge plugin reads them at C4D startup. macOS: open -a "Cinema 4D" --env C4D_MCP_TOKEN=... (or export in your shell profile before launch). Windows: set as User environment variables and restart C4D.

To change the bridge socket, set C4D_MCP_PORT (and optionally C4D_MCP_HOST — see Security) alongside C4D_MCP_TOKEN in the same env map, plus the C4D launch env.

Tools

72 tools across 17 groups. The LLM picks tools itself based on the prompt — you rarely invoke them directly. See docs/TOOLS.md for the full table with per-tool descriptions.

Entity handles

Every CRUD tool identifies entities by a typed handle object. The resolver raises on ambiguous names — prefer path when a scene contains duplicates.

name lookups are strict: if several entities share the name, the bridge returns an error listing up to five candidate paths so you can switch to a path-based handle. create_entity always returns the freshly-resolved handle (objects include path; shaders include both name and index) so chained edits stay stable.

Installing the bridge plugin

Grab the latest cinema4d_mcp_bridge-<version>.zip from Releases and extract the inner cinema4d_mcp_bridge/ folder into your Cinema 4D plugins directory:

You can also register a custom search path via Cinema 4D's Preferences → Plugins → Add and extract the zip there instead.

Launch (or restart) Cinema 4D after extracting. The plugin only reloads when C4D restarts.

Keep the plugin version pinned to the npm package version you run — a version mismatch surfaces as unknown command: <tool> in the bridge log. See CONTRIBUTING.md if you want to run a development checkout instead.

[!NOTE] Official releases only come from two places: the npm package @kumoproductions/mcp-cinema4d and the GitHub Releases page under kumoproductions/mcp-cinema4d. If you obtained a zip or a scoped npm package from anywhere else claiming to be this plugin, treat it as untrusted.

Configuration

Multiple Cinema 4D instances

Off by default. Set C4D_MCP_ENABLE_MULTIINSTANCE=1 on the MCP server to drive several Cinema 4D processes from one server — e.g. a scratch instance for a heavy test render while the primary scene stays untouched.

• list_instances shows every reachable instance. Instance 0 is the primary (C4D_MCP_PORT); the others live on C4D_MCP_PORT + id, so ids stay stable across server restarts and instances a previous session launched are picked up again.
• launch_instance starts another Cinema 4D with g_allowParallelInstance=true (Cinema 4D's own switch that lifts its one-instance-per-installation rule), its own bridge port, and the server's environment — token and opt-ins included. A cold start takes 1–2 minutes and several GB of RAM per instance; C4D_MCP_MAX_INSTANCES caps the total (default 3, primary included).
• Every other tool gains an optional instance argument. Calls without it go to the active instance (set_active_instance). When issuing calls in parallel against different instances, pass instance explicitly — the active instance is shared session state.
• stop_instance quits a secondary instance, discarding its unsaved documents. It never targets instance 0, and the bridge only honours quit when C4D_MCP_ENABLE_MULTIINSTANCE is set in its own environment — true for launched instances, not for a Cinema 4D you started yourself.
• Instances launched by the server keep running when the server exits. All instances share one preferences folder, and the last one to quit writes the preferences — avoid changing settings in scratch instances.

Security

Even without exec_python, many tools mutate state: call_command, set_params, import_scene, render, remove_entity, save_document, open_document, new_document. Treat the bridge like a local shell, not a sandbox.

• exec_python is opt-in. It runs unrestricted Python on Cinema 4D's main thread (file I/O, subprocess, network). Hidden and rejected by the bridge unless C4D_MCP_ENABLE_EXEC_PYTHON=1 is set on both the MCP server process and the Cinema 4D process. Turn it back off when you no longer need it — set-and-forget is how accidents happen.
• Python-bearing plugin types are opt-in too. Python tag (Tpython), Python generator (Opython), MoGraph Python effector, Python field (Fpython), and the Xpresso Python operator all store caller-supplied source code in their container and run it on scene evaluation — i.e. they are RCE-equivalent to exec_python. The bridge refuses create_entity, set_params, apply_xpresso_graph, and take_override operations targeting these types unless C4D_MCP_ENABLE_PYTHON_OPS=1 is set on the Cinema 4D side. Listing / reading / removing existing instances is unaffected.
• Set a shared-secret token (C4D_MCP_TOKEN). Localhost is not a trust boundary — any local process running as your user can otherwise connect. See Client configuration for the JSON snippet.
• Loopback default + remote opt-in. The bridge binds to 127.0.0.1 by default. Binding C4D_MCP_HOST to a non-loopback interface refuses to start unless C4D_MCP_ALLOW_REMOTE=1 is also set — guarding against a one-character typo (0.0.0.0) exposing C4D to the LAN.
• Multi-instance mode spawns processes. With C4D_MCP_ENABLE_MULTIINSTANCE=1, launch_instance starts Cinema 4D executables. The binary comes only from C4D_MCP_EXE or the default install location — never from tool arguments — and the new process inherits the server's environment, so the token and every C4D_MCP_ENABLE_* opt-in apply to it as well. Off by default.
• Only connect MCP clients you trust. Review their tool-use permissions so mutating tools (especially exec_python if opted in) are not auto-approved.
• Indirect prompt injection via scene content. Scene data (object names, parameter strings, imported file paths) flows back to the LLM through list_entities / describe / get_container / dump_shader / get_mesh. When exec_python is enabled, a malicious string in a scene can steer the model into running arbitrary Python. Don't run import_scene against untrusted .c4d / .fbx / .abc files while exec_python is on, and rely on your MCP client's per-call approval for exec_python / call_command / save_document / import_scene rather than blanket-approving them.
• Audit log. Every exec_python call records the code body to the local bridge log (%TEMP%/cinema4d_mcp_bridge.log on Windows, $TMPDIR/cinema4d_mcp_bridge.log on macOS) for after-the-fact review. The log is append-only with no rotation — prune it manually if it grows.

export C4D_MCP_TOKEN="$(openssl rand -hex 16)"   # set in C4D launch env too
npx -y @kumoproductions/mcp-cinema4d

Troubleshooting

Still stuck? Open an issue with the bridge log, your OS, Cinema 4D version, and the tool call that failed.

Known limitations

• modeling_command make_editable is unreliable on Cinema 4D 2026. The SDK's SendModelingCommand handling of MCOMMAND_MAKEEDITABLE shifts across builds — sometimes it returns the new polygon object, sometimes it removes the source without inserting a replacement. Use current_state_to_object instead when you need a guaranteed polygon copy (the bridge inserts the result for you and returns its handle).
• list_graph_node_assets can return an empty list on builds where the Maxon asset repository doesn't expose node-template assets through the usual query path. The tool still returns supported: true with shape-correct output; treat an empty assets array as "discovery unavailable on this C4D build" and pass $type asset ids you already know (e.g. from list_graph_nodes on an existing material).
• Node material friendly names vary. apply_graph_description accepts the declarative $type strings documented by Maxon (e.g. "Standard Material"), but the resolver varies between 2024 / 2025 / 2026 builds — when in doubt, pass the fully-qualified asset id returned by list_graph_node_assets / list_graph_nodes instead.
• exec_python is the only way to seed classical-shader fixtures. A handful of E2E tests (for dump_shader) need to build a shader tree before asserting on it, so they skip cleanly when C4D_MCP_ENABLE_EXEC_PYTHON isn't set on both sides. The tools themselves don't require exec_python.
• Older Cinema 4D versions are not tested. The CI + E2E suite targets C4D 2026. The bridge guards optional SDK constants with getattr fallbacks, so most tools likely work on 2024 / 2025 as well — but we don't verify that and won't accept bug reports that don't reproduce on 2026.

Contributing

See CONTRIBUTING.md for setup, the development loop, how to add a new tool, coding style, and the PR flow.

License

MIT © 2026 kumo.productions, Inc.

Trademarks

Cinema 4D® and Maxon® are trademarks of Maxon Computer GmbH. This project is an independent, unofficial tool, not affiliated with or endorsed by Maxon.