# 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