Initial commit: Hermes-Houdini Bridge

- Shelf tool to open/close command port in Houdini - hhb client script (eval, script, get-selected, set-param, etc.) - Hermes skill with standard hou module workflows - Example: create pyro setup - hou module quick reference
2026-07-12 12:14:36 +00:00
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+# Hermes Skill: Houdini Bridge
+
+Standard workflows to control a running Houdini session via the hermes-houdini-bridge.
+
+## Trigger
+
+When the user asks to:
+- Modify node parameters in Houdini
+- Build node setups/networks in Houdini
+- Write VEX/Wrangle code in Houdini
+- Query selected nodes, connections, or scene state
+- Execute Python in a running Houdini session
+
+## Prerequisites
+
+1. User must have the Hermes Bridge shelf tool active in Houdini (port 12345 open)
+2. SSH access to the Houdini workstation (default: `niklas@192.168.178.39`)
+
+If the bridge is not open, tell the user: "Open the Hermes Bridge shelf tool in Houdini first."
+
+## Client Location
+
+`/opt/data/projects/hermes-houdini-bridge/hermes/bin/hhb`
+
+Always use this full path — the script handles SSH and hcommand internally.
+
+## Common Workflows
+
+### 1. Query Selected Nodes
+
+```bash
+/opt/data/projects/hermes-houdini-bridge/hermes/bin/hhb get-selected
+```
+
+### 2. Set a Parameter
+
+```bash
+/opt/data/projects/hermes-houdini-bridge/hermes/bin/hhb set-param <parm_name> <value>
+```
+Example: `hhb set-param file /path/to/texture.exr`
+
+### 3. Get a Parameter Value
+
+```bash
+/opt/data/projects/hermes-houdini-bridge/hermes/bin/hhb get-param <parm_name>
+```
+
+### 4. Execute Arbitrary Python
+
+```bash
+/opt/data/projects/hermes-houdini-bridge/hermes/bin/hhb eval "<python_code>"
+```
+
+The code runs in Houdini's Python environment with full `hou` module access.
+
+### 5. Check Connection
+
+```bash
+/opt/data/projects/hermes-houdini-bridge/hermes/bin/hhb status
+```
+
+## Useful hou Module Patterns
+
+### VEX in a Wrangler
+```python
+node = hou.selectedNodes()[0]
+node.parm('snippet').set('@P.y += sin(@Frame * 0.1);\n@Cd = rand(@ptnum);')
+```
+
+### Build a Node Chain
+```python
+obj = hou.node('/obj')
+geo = obj.createNode('geo', 'my_setup')
+null_in = geo.createNode('null', 'IN')
+wrangle = geo.createNode('attribwrangle', 'compute')
+null_out = geo.createNode('null', 'OUT')
+wrangle.setInput(0, null_in)
+null_out.setInput(0, wrangle)
+wrangle.parm('snippet').set('@Cd = rand(@ptnum);')
+wrangle.moveToGoodPosition()
+null_out.moveToGoodPosition()
+```
+
+### Read Node Info
+```python
+n = hou.selectedNodes()[0]
+info = {
+    'path': n.path(),
+    'type': n.type().name(),
+    'parms': {p.name(): p.eval() for p in n.parms() if not p.isAtDefault()},
+    'inputs': [c.inputNode().path() for c in n.inputConnections()],
+    'outputs': [c.outputNode().path() for c in n.outputConnections()],
+}
+print(info)
+```
+
+### Create a Material
+```python
+matnet = hou.node('/mat')
+principled = matnet.createNode('principledshader::2.0', 'my_material')
+principled.parm('basecolorr').set(1.0)
+principled.parm('basecolorg').set(0.2)
+principled.parm('basecolorb').set(0.1)
+principled.parm('rough').set(0.3)
+```
+
+## Pitfalls
+
+- Complex Python with quotes/backticks: Use `hhb script file.py` instead of `hhb eval "..."` 
+- Parameter names are internal (e.g., `file`, not `File`)
+- Node types: check with `node.type().name()` first
+- hcommand timeouts: complex scripts may take time, especially if triggering cooks
+- Selected node counts: always check `len(hou.selectedNodes())` before operating