Dive into the powerful synergy of Houdini and Unreal Engine’s PCG system! Learn how SideFX Technical Artist Mohamad Salame crafts massive, dynamic worlds, from modular coliseums to intricate landscapes, using advanced procedural techniques.
Ever wondered how massive, detailed game worlds are built with incredible efficiency and flexibility? In the illuminating workshop “All Roads Lead to Hou-PCG,” Mohamad Salame, a talented Technical Artist at SideFX Labs, unveils a robust workflow for connecting Houdini’s unparalleled procedural power with Unreal Engine’s PCG (Procedural Content Generation) system. This session, originally presented at EPC 2025 HIVE, is a goldmine for technical and environment artists aiming to create vast, iteratively designed environments. Mohamad’s approach emphasizes modularity and attribute-driven instancing, allowing for seamless collaboration and rapid iteration on large-scale projects.
All Roads Lead to Hou-PCG | Mohamad Salame | SideFX | EPC 2025 HIVE by Houdini
The Core Hou-PCG Workflow
At the heart of this workflow lies the powerful concept of “Copy to Points” in Houdini, which finds its counterpart in Unreal’s PCG with the “Match and Set Attributes” node. Mohamad demonstrates how to prepare your meshes in Houdini, assigning unique ‘piece’ attributes to a meticulously crafted point cloud. This point cloud acts as the blueprint, carrying vital information like ‘orient’ for rotation and ‘scale’ (normalized to Unreal’s units) that dictates how instances will be spawned in Unreal. For a deeper dive into the basics, check out this Intro to Houdini and PCG tutorial.
Seamless Export with Alembic
When it comes to exporting your meticulously prepared data from Houdini to Unreal, Mohamad Salame highlights the Alembic (.abc) format as the recommended choice, especially for Unreal Engine 5.4 and later. The beauty of Alembic is its ability to preserve all those crucial attributes you’ve painstakingly set up in Houdini, ensuring that your procedural intent translates perfectly into Unreal’s PCG system.
Unreal Engine PCG Setup: Bringing Worlds to Life
Once your Alembic file is in Unreal, the magic truly begins. A “Static Mesh Spawner” within PCG is configured to leverage a data asset. This data asset, created using Unreal’s robust Data Asset system, essentially maps your Houdini mesh IDs to specific static meshes in Unreal. The “Get Property from Object Path” node plays a key role here, feeding your data asset into the “Match and Set Attribute” node. The creator further showcases the incredible flexibility of overriding multiple materials per mesh, even simplifying the process by renaming material slots. He provides compelling examples, from applying custom materials based on ambient occlusion to dynamically swapping proxy meshes with final high-fidelity versions.
Advanced Techniques & the Colosseum Example
Mohamad takes us through the intricate process of building a fully playable, procedural coliseum. He details how complex modular setups are managed within Houdini using HDAs (Houdini Digital Assets) paired with Python states. These HDAs output both point clouds and mesh lists, ready for PCG. For managing mesh variations, he introduces a clever solution: concatenating mesh IDs and variant IDs into a single string attribute, overcoming the ‘Copy to Points’ limitation. Batch exporting numerous meshes is streamlined using Python scripts, and a scriptable tool is even presented to autofill Unreal’s data assets by extracting IDs from mesh names – a true time-saver! For those interested in exploring the coliseum project files, you can find them on the SideFX Content Library.
Dynamic Cloth and Interactive Radial Placement
The tutorial also delves into creating dynamic cloth elements for the coliseum. While splines were initially considered, the creator opted for pre-made static meshes for performance. He demonstrates simulating hanging cloth in Houdini using Vellum, then integrating these simulated meshes. A standout feature is the “Place Radial Geometry” node in Houdini, which allows for interactive placement and manipulation of modules in a radial fashion. Thanks to Python states, artists can interact directly in the viewport – adding, duplicating, deleting, and changing mesh IDs with simple mouse actions and key modifiers (Control, Shift).
Iterative Design and Material Crafting
A core tenet of this workflow is flexibility. Mohamad illustrates how to save and load complex setups using JSON files, enabling artists to quickly recall and iterate on previously configured layouts. Material overrides can also be dynamically implemented in Unreal by referencing specific mesh IDs within the PCG graph. He even touches upon crafting beautiful painterly materials using world-aligned textures and custom node networks, complete with noise, distortion, feathering, and careful attention to gamma correction for normal maps. This level of detail ensures artistic vision is maintained throughout the procedural process.
Why Hou-PCG Matters for Modern World Building
Mohamad Salame’s workshop powerfully demonstrates that the combination of Houdini and Unreal PCG is not just about spawning objects; it’s about creating a living, breathing, and incredibly flexible pipeline for world-building. For technical artists, this means unprecedented control and efficiency. For environment artists, it means the ability to iterate rapidly on vast landscapes and intricate structures, ensuring artistic quality without sacrificing performance or flexibility. The procedural nature of Houdini, coupled with Unreal’s powerful instancing capabilities, truly makes “All Roads Lead to Hou-PCG” a mantra for modern game development, showcasing the remarkable capabilities Mohamad and the SideFX Labs team are bringing to the industry.
Source:
Houdini – All Roads Lead to Hou-PCG | Mohamad Salame | SideFX | EPC 2025 HIVE
