Unreal Engine Expert Launches ‘Great Hitch Hunt’ Initiative to Eliminate Stutters in UE Games, Provides Developer Tips

Confronting Stuttering Issues in Unreal Engine Games: Insights from Unreal Fest 2025

At Unreal Fest 2025 held in Orlando, Florida, Senior Software Engineer Ari Arnbjörnsson addressed a critical issue for PC gamers: stuttering in games developed with Unreal Engine. With an influx of recent titles marred by performance hiccups, the gaming community has been left questioning Epic Games’ response to this persistent problem.

The Heart of the Matter: ‘The Great Hitch Hunt’

In his intriguingly themed presentation titled ‘The Great Hitch Hunt’, Arnbjörnsson donned a witch hunter’s costume and challenged developers to actively eliminate the causes of stuttering. He outlined seven primary factors contributing to these gameplay disruptions and provided actionable best practices for developers aiming to enhance performance.

Identifying the Stuttering Culprits

1. Level Streaming Issues

The first major culprit is Level Streaming, which encompasses various hitches related to the dynamic loading and unloading of game environments. Arnbjörnsson noted that the improper use of static mesh actors—such as complex objects like tables and utensils—can significantly burden game performance, particularly in expansive AAA worlds. To mitigate these issues, he advocated for the use of instanced static meshes (ISMs) or hierarchical instanced static meshes (HISMs), as well as utilizing the packed level actors feature to condense numerous static meshes into fewer, less resource-intensive actors. Additionally, he mentioned upcoming advancements in Unreal Engine 5.5’s Cell Transformers, designed to automatically convert static mesh actors into instanced meshes at runtime.

2. Physics Optimization

Another source of hitches arises from physics-related processing. Developers often underestimate the need for optimization, especially following the introduction of Nanite technology in Unreal Engine 5, which leads to an assumption that complex meshes will perform seamlessly. Instead, Arnbjörnsson recommends employing simpler collision shapes—starting with spheres, then capsules, followed by boxes, and finally convex polygons. He also emphasized the importance of disabling physics interactions for distant, non-interactive objects. Epic’s experimental Async Physics Initialization feature aims to alleviate the physics burden on the game thread, but developers are advised to approach it cautiously.

3. Actor Spawning Delays

Actor Spawning delays represent the next significant challenge. Heavy actors equipped with multiple components, such as character models, can create noticeable drops in frame rates during their initialization. To address this, Arnbjörnsson suggested limiting the number of actors spawned each frame, deferring the activation of actors’ components, and implementing actor pooling strategies to reuse existing objects rather than repeatedly destroying and recreating them. Though the implementation of actor pooling as a default feature in Unreal Engine is under consideration, developers are currently encouraged to create tailored pools for their specific actor types.

4. Pipeline State Object (PSO) Compilation

One of the most prevalent causes of stuttering is related to Pipeline State Object (PSO) compilation. Unlike consoles, which boast uniform hardware configurations, PCs face challenges with shader compilation during gameplay, leading to stuttering when shaders must be compiled on-the-fly. While PSO precaching was introduced in Unreal Engine 5.3 to alleviate this issue, developers still need to devise their own PSO compilation strategies and leverage tools such as the PSO Cache Buster plugin to optimize performance further.

5. Garbage Collection Spikes

Garbage Collection can also lead to performance hitches when excessive unused UObject instances accumulate, prolonging the garbage collection process. Developers should actively manage UObject counts and intelligently schedule garbage collection to minimize disruptions. Epic is currently exploring an experimental Incremental Reachability Analysis feature, aimed at distributing garbage collection tasks over multiple frames to alleviate these issues.

6. Synchronous Loading Hitches

Synchronous loading hitches occur when the game thread is stalled by blocking asset loads, leading to frustratingly long interruptions. To combat this, developers must strictly employ asynchronous loading techniques and use asset validators like Arnbjörnsson’s CommonValidators to track problematic loading behaviors. Unreal Engine versions 5.4 and 5.5 aim to improve the situation by introducing features that allow for partial flushing of async queues.

7. Blueprint and Content Hitches

Finally, performance can be hindered by overcomplicated Blueprints and content scripts, which may involve excessive timers, frequent updates, or bloated sequences. To assist developers, Epic is enhancing the Unreal Insights tool, making it easier to visualize and rectify performance bottlenecks within projects.

Conclusion: Embracing Optimization Challenges

In wrapping up his presentation, Arnbjörnsson emphasized that while advancements in technology continually reshape the gaming landscape, developers must remain conscious of inherent limitations. Effective optimization strategies and creative problem-solving remain essential for delivering the smoothest gaming experiences possible. His session aimed not only to inform but also to inspire developers to take action against stuttering issues in their projects.

For further details, watch the full talk

here

Source & Images