Hermes-Houdini Bridge

Hermes Agent ↔ Houdini Python Bridge — remote node control, parameter editing, VEX injection, and scene querying via Houdini's built-in hcommand protocol.

Architecture

Hermes Agent (orange-desktop)          Houdini 21.0 (fedora.fritz.box)
┌─────────────────────┐                ┌──────────────────────────────┐
│  hhb eval "code"    │──SSH──────────→│  hcommand PORT "python code" │
│  hhb script file.py │                │       ↓                      │
│  hhb get-selected   │                │  hou module (running session) │
└─────────────────────┘                └──────────────────────────────┘

No custom server needed — uses Houdini's built-in openport + hcommand protocol. The bridge wraps SSH and command quoting so Hermes can send Python code to your live Houdini session.

Quick Start

1. Install the Shelf Tool (once)

Copy houdini/shelf/hermes_bridge.shelf to your Houdini toolbar, or run the shelf script directly in Houdini's Python Shell.

2. Open the Bridge (every session)

Click the Hermes Bridge shelf button in Houdini. It opens port 12345 and shows a status dialog.

3. Use from Hermes

# Get selected node info
./hermes/bin/hhb get-selected

# Set a parameter
./hermes/bin/hhb eval "hou.selectedNodes()[0].parm('file').set('/path/to/file.abc')"

# Query connections
./hermes/bin/hhb eval "print(hou.selectedNodes()[0].inputConnections())"

# Execute a complex Python script
./hermes/bin/hhb script ./examples/create_pyro_setup.py

Requirements

• Houdini 20+ (tested with 21.0)
• SSH access from Hermes host to Houdini workstation
• Network connectivity (port 12345, default)

Project Structure

hermes-houdini-bridge/
├── houdini/
│   └── shelf/
│       └── hermes_bridge.shelf    # Shelf tool: open/close port
├── hermes/
│   ├── bin/
│   │   └── hhb                    # Client: send commands to Houdini
│   └── skill/
│       └── SKILL.md               # Hermes skill for standard workflows
├── examples/
│   └── create_pyro_setup.py       # Example: build a pyro sim
├── docs/
│   └── REFERENCE.md               # hou module cheat sheet
└── README.md

Security

• Port 12345 opens on 0.0.0.0 — only use on trusted networks
• To restrict to localhost: modify the shelf tool's openport call to hou.hscript('openport 12345 +.+.+.+')
• The bridge uses Hermes' existing SSH key — no additional credentials needed

Troubleshooting

Symptom	Fix
hcommand: connect failed	Port not open. Click shelf button in Houdini.
hcommand: connection refused	Houdini not running or port blocked by firewall.
Python error in output	Code has syntax issues. Test in Houdini Python Shell first.
ModuleNotFoundError: No module named 'hou'	Running hython directly, not through hcommand. Use hhb.