Building a Procedural Destruction Pipeline with Houdini and Unreal Engine 5
Lea Seiler and Vishwaas Khare spoke with us about the workflow behind the Procedural Chaos Destruction Framework, explaining how they used Houdini to create a scalable and performant fracture logic, and discussing how they integrated various Unreal Engine systems.
Introduction
Destruction in modern games sits at the intersection of visual fidelity, performance, and production scalability. While Unreal Engine's Chaos system provides powerful real-time simulation capabilities, building a controlled and artist-friendly pipeline around it is essential for production use.
PROJECT MAYHEM presents a procedural destruction workflow that bridges Houdini and Unreal Engine 5, enabling the generation of optimized, game-ready destruction assets with a high degree of control over fracture behavior, clustering, and performance budgets.
Houdini is used to author procedural fracture logic and asset variations, while Unreal Engine integrates these assets through Chaos, Dataflow, and Blueprint-driven systems to ensure predictable behavior, gameplay responsiveness, and efficient runtime execution.
This article breaks down the full pipeline, highlighting how each system contributes to creating scalable, controllable, and visually cohesive destruction in a real-time environment.
Houdini Digital Asset Workflow
The cutter logic
In this segment, we explore how Houdini can generate a scalable and performant fracture logic for Unreal Engine's Chaos System. A stable workflow relies on three components: a robust cutter setup, defined piece and cluster attributes, and properly configured Geometry Collection attributes. For PROJECT MAYHEM, the cutter logic was designed to support a realistic art direction by combining both Voronoi and Boolean fracture in our cutter logic.
Voronoi fracture is used to select the inside faces, which are then remeshed, enhanced with procedural noise, and finally UV unwrapped. This setup works as the foundation for the Boolean fracture. Additional cutter meshes, in the form of subdivided grids with added noise, are then copied to points in a randomized rotation, introducing controlled irregularities.
Adjusting the point distribution and density offers control over the piece count as well as features such as using localized fracture through input vertex color masks, allowing artists to direct damage in a focused, art-driven manner. This approach offers control over the art direction and performance, while giving artists control over the fracture behavior in Unreal Engine 5.
Attributes and Geometry Collections
To enable seamless interaction with Unreal Engine's Chaos system, a set of custom attributes is defined to convert the asset into a Geometry Collection. This allows Unreal Engine to differentiate between root, cluster, and individual fractured pieces.
During the Boolean fracture stage, a name attribute is generated, assigning each fractured primitive a unique ID. The RBD cluster node then groups these pieces using the cluster attribute. Exposed parameters such as cluster size and detach ratio offer artists direct control over how these clusters are formed and how they break apart during impact.
Additional Geometry Collection attributes are introduced to drive physical behavior, including collision setup, mass distribution, and damage thresholds. These attributes are critical for balancing art direction with performance while ensuring predictable and controllable destruction behavior in Unreal Engine.
Unreal Engine Integration
After assigning the HDA to a static mesh inside Unreal Engine, the tool generates a Geometry Collection ready for interaction with the Chaos System. The HDA exposes a custom parameter menu with three performance budget presets, ensuring 60 fps for low, mid, and high-end hardware.
UVs are automatically transferred from the source mesh to the Geometry Collection, ensuring UV consistency, while predefined attributes drive realistic and performant breakage behavior, and integration with Dataflow, Niagara Systems, and Blueprints enables full control over runtime interactions and visual effects.
Weapon Interaction and Gameplay Trigger
Once the HDA is baked into a Geometry Collection, the weapon logic comes into action. Upon firing, a line trace is executed from the player camera, taking into account both its position and rotation. If the trace results in a successful hit, a Blueprint Component is triggered, which drives the Niagara-based bullet impact VFX while also sending an interface event through a Blueprint Interface.
This interface event establishes the connection with the Geometry Collection Blueprint, allowing gameplay logic to remain decoupled from the destruction system while still enabling seamless communication between the two.
Geometry Collection Logic
When the "Apply Bullet Strain" interface event is received, the Geometry Collection responds by spawning a "Field System" at the impact location.
The behavior of this field is highly controllable, with parameters such as radius determining the area of influence, and additional attributes like radial magnitude, directional magnitude, torque, strain intensity, and strain falloff shaping how the force propagates through the structure.
Niagara VFX and Data Channel Logic
While the fracture system defines the physical reaction, Niagara is responsible for delivering the visual impact. To ensure scalability and performance, Niagara Data Channels are used to batch and route spawn events instead of triggering individual effects for each hit.
When an impact occurs, relevant data is written into the data channel, which is then read by the Niagara system.
Within the emitter, the data channel is accessed, and the appropriate emitter ID is supplied, allowing spawn conditions to be evaluated based on the incoming payload. Once particles are spawned, the data channel is referenced again to read additional data and drive behavior adjustments. This workflow keeps VFX tightly synchronized with gameplay events while minimizing overhead and maintaining efficient runtime performance.
Dataflow Asset Logic
For the destruction authoring pipeline, Unreal Engine's Dataflow system was also used to build a procedural and non-destructive workflow. This allowed fracture logic to be defined once and reused across multiple assets, making the system highly modular.
In practice, a single Dataflow graph was created to represent concrete fracture behavior and then applied consistently to different Geometry Collections. This approach enabled rapid iteration, as changes could be made directly within the graph and instantly reflected in the result.
Internal Material Logic
To improve visual fidelity, special attention was given to the internal faces revealed during fracture. A custom baking step was integrated into the Dataflow graph to generate thickness, curvature, and ambient occlusion data for these internal surfaces, which were then packed into an RGB mask.
This mask was used to blend between external and internal material layers that respond to the fracture. This mask data is used to control Base Color, Roughness, and other properties so the exposed surfaces look natural and consistent.
Conclusion
Working on PROJECT MAYHEM has been an invaluable experience in understanding how procedural workflows can bridge the gap between visual fidelity and real-time performance.
