unreal-pcg-python

name

unreal-pcg-python

description

Guide for Unreal Engine 5.x PCG (Procedural Content Generation) Python integration. Covers the PCGPythonInterop plugin, the Execute Python Script node, PCG Python API (PCGComponent, PCGBlueprintElement, PCGSpatialData, PCGPointData), editor automation, custom PCG nodes via Python, and known limitations. Use when the user asks about PCG Python, PCGPythonInterop, Execute Python Script node, Python scripting for procedural generation, automating PCG graphs with Python, or creating custom PCG nodes with Python/Blueprint.

Unreal Engine PCG Python Integration Guide

Overview

Python interacts with UE5's Procedural Content Generation (PCG) framework at two levels:

1. PCGPythonInterop Plugin (UE 5.5+, Beta) -- An editor-only PCG graph node ("Execute Python Script") that runs Python code mid-graph.
2. PCG Python API (UE 5.2+) -- Standard unreal module classes (PCGComponent, PCGBlueprintElement, etc.) for editor automation and custom node logic.

Important: All PCG Python functionality is editor-only. Python cannot run in packaged builds or at game runtime.

Official Documentation

Resource	URL
PCG Framework Overview	https://dev.epicgames.com/documentation/en-us/unreal-engine/procedural-content-generation-overview
PCG Framework Landing Page	https://dev.epicgames.com/documentation/en-us/unreal-engine/procedural-content-generation-framework-in-unreal-engine
PCG Development Guides	https://dev.epicgames.com/documentation/en-us/unreal-engine/pcg-development-guides
PCG Node Reference	https://dev.epicgames.com/documentation/en-us/unreal-engine/procedural-content-generation-framework-node-reference-in-unreal-engine
PCG Data Types Reference	https://dev.epicgames.com/documentation/en-us/unreal-engine/procedural-content-generation-framework-data-types-reference-in-unreal-engine
PCGPythonInterop Plugin API	https://dev.epicgames.com/documentation/en-us/unreal-engine/API/PluginIndex/PCGPythonInterop
Python Editor Scripting	https://dev.epicgames.com/documentation/en-us/unreal-engine/scripting-the-unreal-editor-using-python
PCGComponent Python API	https://dev.epicgames.com/documentation/en-us/unreal-engine/python-api/class/PCGComponent
PCGBlueprintElement Python API	https://dev.epicgames.com/documentation/en-us/unreal-engine/python-api/class/PCGBlueprintElement
PCGBlueprintHelpers Python API	https://dev.epicgames.com/documentation/en-us/unreal-engine/python-api/class/PCGBlueprintHelpers
PCGSpatialData Python API	https://dev.epicgames.com/documentation/en-us/unreal-engine/python-api/class/PCGSpatialData
PCGPointData Python API	https://dev.epicgames.com/documentation/en-us/unreal-engine/python-api/class/PCGPointData
Python Interop Roadmap	https://portal.productboard.com/epicgames/1-unreal-engine-public-roadmap/c/2213-python-interop-plugin

Community Resources

Resource	URL
Forum: Create PCG Graph with Python	https://forums.unrealengine.com/t/create-pcg-graph-with-python/1714891
Forum: Generate PCG through Python	https://forums.unrealengine.com/t/generate-pcg-through-python-script/2053107
Forum: Change PCG Parameters from Python	https://forums.unrealengine.com/t/how-to-change-pcg-graph-parameters-from-python/2060532
Custom PCG Nodes Guide (Blueshift)	https://blueshift-interactive.com/2025/09/03/how-to-create-custom-pcg-nodes/
PCG Extended Toolkit (community C++ plugin)	https://github.com/PCGEx/PCGExtendedToolkit
Houdini to PCG Data Example	https://github.com/cgtoolbox/HoudiniToPCGDataExample

---

1. PCGPythonInterop Plugin ("Execute Python Script" Node)

Plugin Details

• Location: Engine/Plugins/PCGInterops/PCGPythonInterop/
• Status: Beta (IsBetaVersion: true, EnabledByDefault: false)
• Module: PCGPythonInteropEditor (Editor-only)
• Dependencies: PCG plugin + PythonScriptPlugin

Enabling the Plugin

1. Enable Python Editor Script Plugin (under Plugins > Scripting)
2. Enable PCG Python Interop (under Plugins > Procedural Content Generation)
3. Restart the editor

The "Execute Python Script" Node

This is the only node the plugin adds. It runs Python code within a PCG graph.

Two input modes:

Mode	Description
Input	Reads Python source from an FString attribute on the "Source" pin, or uses an inline default script
File	Executes a .py file from disk

Key characteristics:

• Runs on main thread only (Python GIL constraint)
• Not cacheable -- re-executes every time the graph runs
• No data output -- output pin is dependency-only (for execution ordering)
• Shows an editor toast on execution (suppressible via bMuteEditorToast)
• Default inline script: print("Hello PCG World!")

Settings (UPROPERTY):

ScriptInputMethod  -- EPCGPythonScriptInputMethod (Input or File)
ScriptSource       -- FPCGAttributePropertyInputSelector (which attribute holds the script)
ScriptPath         -- FFilePath (path to .py file, filtered to *.py)
bMuteEditorToast   -- bool (suppress editor notification)

All properties marked PCG_Overridable (can be set via PCG parameter overrides).

Planned Future Features (from source TODOs)

• EvaluateStatement mode for line-by-line feedback
• Parameter inputs/outputs (get/set variables from within Python, like Blueprint/HLSL nodes)
• Generalized source editor in PCG for HLSL + Python
• Potential multi-thread support

---

2. PCG Python API (Editor Automation)

These classes are available via import unreal in any UE Python script, independent of the PCGPythonInterop plugin.

Create PCG Graph Assets

import unreal

asset_tools = unreal.AssetToolsHelpers.get_asset_tools()
graph = asset_tools.create_asset(
    'MyPCGGraph', '/Game/PCG',
    unreal.PCGGraph, unreal.PCGGraphFactory()
)

Trigger PCG Generation

# Get PCGComponent from an actor
pcg_comp = actor.get_component_by_class(unreal.PCGComponent)

pcg_comp.generate(True)          # force full regeneration
pcg_comp.generate_local(True)    # local only, no replication
pcg_comp.set_graph(my_graph)     # swap graph asset
pcg_comp.seed = 42               # set deterministic seed
pcg_comp.cleanup(True, False)    # cleanup generated components

Work with Spatial Data

# PCGSpatialData operations
spatial_data.to_point_data()              # convert to points
spatial_data.intersect_with(other)        # boolean intersection
spatial_data.union_with(other)            # boolean union
spatial_data.subtract(other)              # boolean subtraction
spatial_data.get_bounds()                 # get spatial bounds
spatial_data.get_density_at_position(pos) # sample density

# PCGPointData
point_data = unreal.PCGPointData()
points = point_data.get_points()          # -> Array[PCGPoint]
point_data.set_points(modified_points)

PCGBlueprintHelpers (Utility Functions)

helpers = unreal.PCGBlueprintHelpers
helpers.get_actor_data(context)
helpers.get_component(context)
helpers.get_random_stream_from_point(point, settings, component)
helpers.compute_seed_from_position(position)
helpers.create_pcg_data_from_actor(actor, parse_actor)

---

3. Custom PCG Nodes via PCGBlueprintElement

PCGBlueprintElement is the base class for custom PCG nodes in Blueprint (and theoretically Python). Available since UE 5.2.

Key Overridable Methods

Method	Purpose
execute(input)	Primary execution -- receives and returns PCGDataCollection
execute_with_context(context, input)	Execution with PCG context access
point_loop_body(context, data, point, metadata, iteration)	Per-point processing
variable_loop_body(...)	Per-point, returns variable number of output points
iteration_loop_body(context, iteration, a, b, metadata)	Fixed-count iteration
node_title_override()	Custom display name
node_color_override()	Custom node color

Configurable Properties

element.custom_input_pins    # Array[PCGPinProperties]
element.custom_output_pins   # Array[PCGPinProperties]
element.has_default_in_pin   # bool
element.has_default_out_pin  # bool
element.is_cacheable         # bool
element.requires_game_thread # bool

---

4. Known Limitations

Limitation	Details
Editor-only	No Python in packaged builds or runtime. The node explicitly errors: "Editor-only, should not be used at runtime."
No programmatic node creation	Python cannot add/connect nodes within a PCG graph programmatically (Epic confirmed, as of 2024)
No data output from Execute Python Script	The node only provides execution ordering, not PCG data flow
Main thread only	Python execution blocks the main thread
API churn	Method names changed between 5.2-5.5 (e.g., loop_on_points -> point_loop)
Parameter access is finicky	Setting PCG graph parameters from Python via ParametersOverrides requires navigating complex property bags

5. Version History

UE Version	PCG Status	Python Notes
5.2	Experimental	PCGBlueprintElement, PCGComponent Python API introduced
5.3	Experimental	PCGSpatialData documented, loop API stabilized
5.4	Beta	PCGBlueprintHelpers fully documented
5.5	Beta	GPU compute path, PCGGeometryBlueprintElement added
5.7	Production-Ready	PCGPythonInterop plugin formalized, PCG Editor Mode, ~2x perf

6. Best Practices

• Use Python for automation: Batch asset creation, parameter sweeps, CI/CD pipelines
• Use Blueprint for custom nodes: More stable API, designer-friendly, works in editor
• Use C++ for performance: Multi-threaded, GPU HLSL support, full API access
• Python + PCG sweet spot: Triggering generation across many actors, managing seeds, integrating external data (Houdini, numpy), asset migration scripts