Blender-Mind-MCP (Production AI 3D Modeling & Blender Bridge)

A production-grade Model Context Protocol (MCP) server and Blender Addon ecosystem for automated 3D modeling, procedural asset generation, shader authoring, and multimodal viewport inspection.

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🏗️ Prior Art & Architectural Inspiration

This project incorporates architectural lessons and benchmarks from leading GitHub Blender AI projects (such as ahujasid/blender-mcp and djeada/blender-mcp-server):

1. Thread-Safe Main-Thread Dispatching: Blender’s Python C-API (bpy) is not thread-safe. As discovered in community issue audits, executing bpy calls inside raw socket listener threads triggers memory corruptions and segmentation faults. Our Blender Addon uses a thread-safe queue.Queue coupled with bpy.app.timers to ensure all scene modifications execute strictly in Blender’s main render/GUI loop.
2. Undo Step Isolation: Every AI code execution is bracketed with bpy.ops.ed.undo_push(), enabling seamless Ctrl+Z rollbacks inside Blender.
3. Multimodal Viewport Capture: Uses offscreen OpenGL rendering (bpy.ops.render.opengl) to return Base64-encoded PNG screenshots of the 3D viewport directly to multimodal vision models.
4. Hexagonal Architecture (Ports & Adapters): Decouples pure 3D geometry generation from physical drivers, supporting both Live Socket connections (127.0.0.1:9876), headless CLI batching (blender -b), and offline procedural glTF binary simulation.

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📦 Project Structure

blender-mind-mcp/
├── addon/
│   └── blender_mcp_addon.py       # Full Blender 3.x/4.x Addon (UI Sidebar Panel, Socket Server, Viewport Capture)
├── src/
│   ├── index.ts                   # stdio JSON-RPC MCP Server entry point
│   ├── bridge/
│   │   └── socket_client.ts       # Robust TCP Socket Client with reconnect & timeout handling
│   ├── core/
│   │   └── domain/
│   │       ├── types.ts           # 3D Domain Types (Scene, Mesh, Material, Modifier, Transform)
│   │       ├── scene.ts           # Pure in-memory 3D scene graph & polygon math
│   │       └── bpy_generator.ts   # Modern Blender 4.x/3.x Python code synthesizer
│   ├── ports/
│   │   └── driver.port.ts         # BlenderDriverPort interface specification
│   ├── adapters/
│   │   ├── live_socket.adapter.ts # Live Socket Adapter (talks to active Blender GUI)
│   │   ├── blender_cli.adapter.ts # Headless CLI Adapter (talks to blender.exe)
│   │   └── mock_geometry.adapter.ts # Offline Simulation Adapter (glTF & OBJ binary synthesis)
│   └── tools/
│       └── index.ts               # 10 MCP Tools registry & dispatcher
├── tests/
│   ├── unit/                      # L1: Domain math & Python code generation
│   ├── contract/                  # L2: MCP tool schemas & argument contracts
│   ├── integration/               # L3: Binary glTF headers & TCP Socket Bridge
│   └── run_tests.ts               # Complete Truth Ladder test runner
├── package.json
└── tsconfig.json

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🚀 Quick Start

1. Install Addon in Blender

1. Open Blender (3.6+ or 4.x).
2. Go to Edit > Preferences > Add-ons > Install... (or the Install from Disk arrow in 4.2+).
3. Select addon/blender_mcp_addon.py.
4. Enable Development: Blender MCP Bridge.
5. In the 3D Viewport, press N to open the sidebar, click the Blender MCP tab, and click Start MCP Server.

2. Configure MCP Client (Antigravity / Claude / Codex)

Add to your project or global MCP configuration (.mcp.json):

{
  "mcpServers": {
    "blender": {
      "command": "node",
      "args": [
        "--disable-warning=ExperimentalWarning",
        "--experimental-strip-types",
        "C:/Users/a1691/Documents/antigravity/noble-hypatia/src/index.ts"
      ]
    }
  }
}

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🛠️ 10 Core MCP Tools

Tool Name	Description	Key Capabilities
blender_create_primitive	Create procedural 3D mesh	cube, sphere, cylinder, torus, plane, cone, monkey
blender_apply_modifier	Attach procedural modifiers	subsurf, bevel, boolean, mirror, array, solidify
blender_procedural_material	PBR Principled BSDF shader	base_color, metallic, roughness, transmission (glass), emission
blender_setup_lighting	Position & tune light sources	SUN, POINT, SPOT, AREA (wattage, radius, color tint)
blender_setup_camera	Camera framing & lens	location, look_at tracking, focal_length in mm
blender_capture_viewport	Visual viewport snapshot	Returns Base64 PNG image directly to multimodal LLMs
blender_export_asset	3D model baking & export	.glb, .gltf, .obj, .stl, .fbx
blender_inspect_scene	Topology & scene tree inspection	Hierarchical object list, polycount, vertex count, modifiers
blender_execute_bpy	Raw parameter Python execution	Sandboxed execution with stdout/stderr capture
blender_health	System diagnostics	Reports active driver, port status, and Blender build

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🧪 Truth Ladder Verification

npm test

Executes all 6 test suites across the 4-level Truth Ladder:

• L1 Unit: 100% pure domain modeling & Python code synthesizer AST checks.
• L2 Contract: Schema definitions and dispatch verification for all 10 tools.
• L3 Integration: Binary glTF v2 Header (0x46546C67) & OBJ structure validation.
• L3 Integration: Live TCP Socket Client-Server loopback test on 127.0.0.1:9899.
• L4 E2E: Live stdio JSON-RPC pipe roundtrip.