houdini-python-automation

houdini-python-automation

Version: 1.1.1 Last Updated: 2026-10-09 Dependencies: Houdini 20+, Python 3.9+

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CRITICAL: MANDATORY FIRST STEP

ALWAYS verify Python environment before execution:

import hou

# Verify Houdini session is active
try:
    hip_file = hou.hipFile.path()
    print(f"Active Houdini session: {hip_file}")
except hou.Error:
    print("ERROR: No active Houdini session")
    exit(1)

# Check Python version
import sys
print(f"Python version: {sys.version}")

Why Critical:

• Session Required: HOM (hou module) only works inside Houdini Python shell or hython
• Scene State: Some operations require saved scene (hou.hipFile.save())
• Thread Safety: UI operations must run on main thread

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QUICK START

Most Common Use Case: Batch Node Creation

Goal: Create multiple nodes programmatically and connect them

Step 1: Get Parent Context

import hou

# Get geometry object
obj = hou.node("/obj")
geo = obj.createNode("geo", "procedural_geo")

# Delete default file node
file_node = geo.node("file1")
if file_node:
    file_node.destroy()

Step 2: Create Node Network

# Create grid source
grid = geo.createNode("grid", "source_grid")
grid.parm("rows").set(50)
grid.parm("cols").set(50)

# Create mountain (noise deformation)
mountain = geo.createNode("mountain::2.0", "deform")
mountain.setInput(0, grid)

# Create scatter
scatter = geo.createNode("scatter::2.0", "scatter_points")
scatter.setInput(0, mountain)
scatter.parm("npts").set(5000)

print(f"Created {geo.children()} nodes")

Step 3: Set Display and Render Flags

# Set display flag (what you see in viewport)
scatter.setDisplayFlag(True)
scatter.setRenderFlag(True)

# Layout nodes automatically
geo.layoutChildren()

Step 4: Verify Results

# Check node count
nodes = geo.children()
print(f"Total nodes: {len(nodes)}")

# Check connections
for node in nodes:
    inputs = node.inputs()
    if inputs:
        print(f"{node.name()} <- {[n.name() for n in inputs if n]}")