Epic Games Declares War on PC Game Stuttering with “The Great Hitch Hunt” at Unreal Fest 2025

At Unreal Fest 2025 in Orlando, Florida, Epic Games’ Senior Unreal Engine Software Engineer Ari Arnbjörnsson delivered a keynote presentation titled “The Great Hitch Hunt,” offering a comprehensive technical analysis of performance issues that have long plagued Unreal Engine games on PC. Arnbjörnsson, dressed in a thematic witch hunter outfit, used the stage to rally developers toward a unified goal: eliminating stuttering and hitches through proper development practices and the effective use of new engine tools.

His talk addressed seven major sources of hitches in Unreal Engine titles and detailed both current and upcoming solutions from Epic, as well as best practices for developers.

Level Streaming Overhead

One of the most common performance bottlenecks involves inefficient use of static mesh actors. In large environments, artists often place dozens or hundreds of static assets such as tables, chairs, and utensils individually, resulting in significant memory usage and processing overhead. Arnbjörnsson advised using Instanced Static Meshes (ISMs) and Hierarchical Instanced Static Meshes (HISMs) to consolidate geometry and reduce draw calls.

Epic is currently testing Cell Transformers, a feature in Unreal Engine 5.5 that automatically converts static mesh actors into instances at runtime, and additional streaming improvements planned for Unreal Engine 5.6. These features remain experimental but represent significant potential improvements in handling large, dynamic environments.

Physics Performance

The adoption of Nanite in Unreal Engine 5 has encouraged developers to use high-detail geometry freely, but Arnbjörnsson cautioned that physics systems must still be optimized. He emphasized the use of simplified collision primitives, in order of efficiency: spheres, capsules, boxes, and convex shapes. Distant or non-interactive objects should have collisions disabled entirely.

Epic is also developing Async Physics Initialization (UE5.5/5.6) to move physics setup off the main game thread. However, this feature is still experimental and should be tested rigorously before implementation.

Actor Spawning Bottlenecks

Spawning complex actors particularly those with skeletal meshes and multiple components can introduce frame drops when executed in bulk. Developers are encouraged to limit actor spawns per frame, delay the initialization of non-critical components, and implement actor pooling to recycle instances rather than repeatedly creating and destroying them.

Although Epic has received requests to integrate actor pooling natively into Unreal Engine, the feature’s wide-ranging application across industries makes it a challenge to generalize. For now, developers are advised to implement pooling on a per-project basis.

Shader Compilation and Pipeline State Objects (PSOs)

Stuttering caused by on-the-fly shader compilation is one of the most visible issues in PC games. Unlike consoles, where permutations can be precompiled for fixed hardware, PC games must often compile shaders dynamically. While PSO precaching was introduced in Unreal Engine 5.3, Arnbjörnsson urged developers to formulate tailored caching strategies.

He also recommended the use of his custom tool, PSO Cache Buster, available on GitHub, to identify and profile uncompiled states in real-time. Epic is actively expanding its internal PSO coverage, particularly within Fortnite and Unreal sample projects.

Garbage Collection

Performance spikes due to Garbage Collection (GC) are typically caused by excessive UObject accumulation. Developers should manage object counts carefully and trigger GC events during periods of minimal activity.

Epic is working on Incremental Reachability Analysis, designed to distribute GC tasks over several frames. Additionally, the team is developing a multithread-safe incremental GC for client builds, which will further minimize frame interruptions.

Synchronous Loading

Synchronous asset loading can halt the game thread entirely, leading to noticeable pauses. Developers must adopt asynchronous loading practices wherever possible. Tools such as CommonValidators can help flag synchronous calls. Epic has also begun issuing runtime warnings for blocking loads and introduced partial async queue flushing in UE5.4 and UE5.5 to reduce impact when such loads do occur.

Blueprint and Content Scripting

Hitches related to blueprints and scripts stem from overuse of timers, tick functions, and unnecessary updates. Developers should minimize ticking, remove unneeded logic for distant actors, and optimize sequences to reduce system load. Epic continues to enhance Unreal Insights, its profiling toolset, to support deeper visibility into performance bottlenecks.

Epic’s Ongoing Commitment to Performance

Arnbjörnsson concluded his session by reminding developers that while hardware and engine capabilities have evolved, performance optimization remains a fundamental responsibility of every development team. Unreal Engine offers powerful tools, but thoughtful design, profiling, and constraint-aware development are essential to delivering polished gameplay experiences.

What’s your take on Unreal Engine’s renewed focus on PC optimization? Do you think these tools will be enough to improve game stability moving forward? Let us know in the comments.